The Second International Pawpaw Conference
September 21-22, 2001

Frankfort, Kentucky

Sponsored by
Kentucky State University
and The PawPaw Foundation

With additional support from
The Kentucky Center for Agricultural Development
The Governor’s Agricultural Development Board
Nature’s Sunshine Products

Program and Abstracts

The PawPaw Foundation

Conference Program Committee Members
Kirk Pomper (Chair), Robert Barney, Noland Williams, Charliese Brown, Wyvette Williams, Marion Simon, Snake Jones, Eddie Reed, Mac Stone, Susan Templeton, Jean Ward and Dewayne Ingram

Committee Advisor
Harold R. Benson

Proceedings Associate Editors
Robert Barney and Kirk Pomper

The Kentucky State University Pawpaw Research cover art work was created by Ms. Wyvette Williams and is the property of the Kentucky State University

TABLE OF CONTENTS

Schedule of Events (Friday)
Schedule of Events (Saturday)
Abstracts
Figure 1. Germination percentage of pawpaw seeds after stratification at 5^oC
Figure 2. Germination percentage in two seed lots of pawpaw after storage
Figure 3. Root formation in seedling cuttings treated with 10,000 ppm IBA
Figure 4. Shoot formation from seedling and rejuvenated explants pawpaw
Table 1. Summary of Tree Growth and Fruit Production in 2001 for the KSU Pawpaw Regional Variety Trial in Frankfort, Kentucky
Table 2. Summary of Fruit Production in 2001 for the KSU-UK Pawpaw
Regional Variety Trial in Princeton, Kentucky
Table 3. Survival of Pawpaws at Corvallis, Oregon Regional Variety Trial
Appendix A. Maps
Appendix B. Pawpaw Regional Variety Trial Field Plan
Appendix C. Survival, Growth and Establishment of Grafted Pawpaws in Upstate New York
Appendix D. Repository Accessions at the USDA National Clonal Germplasm Repository for Asimina spp.
 

Schedule of Events

Friday, 9/21/01

  8:00-9:00 am   Registration and Refreshments-KSU Extension Building (Room 238)

  9:00-9:10 am   Introductory Remarks and Welcome
                            Dr. George W. Reid – President of Kentucky State University
                            Dr. Kenoye K. Eke – Vice President for Academic Affairs, KSU
                            Dr. Harold R. Benson – Director of Land Grant Programs, KSU
                            Dr. Kirk W. Pomper – Principal Investigator of Horticulture, KSU

  9:10-9:30 am   Overview of KSU program
   (Abstract 01)  The KSU Pawpaw Program
                           Kirk W. Pomper, Land Grant Program, KSU, Frankfort, KY

  9:30-10:45 am   Propagation Round Table
   (02)            Propagation of Pawpaw
                             Cynthia Finneseth1, Sharon Kester1, Robert Geneve*1,
                             Kirk Pomper2, and Desmond Layne3, 1Dept. of Horticulture,
                             University of Kentucky, 2Land Grant Program, KSU, and 3Dept.
                             of Horticulture, Clemson University (20 min)

   (03)          Induction of Roots on Seedling Cuttings of Pawpaw Following Inoculation
                           with Agrobacterium rhizogenes
                            Greg Dortch, Caula A. Beyl*, and Tomas Ayala-Silva
                            Dept. of Plant and Soil Science, Alabama A&M University (15 min)

    (04)        Container Production of Pawpaw Seedlings
                           Kirk W. Pomper*1, Desmond R. Layne2, and Snake C. Jones1; 1Land
                           Grant Program, 2Dept. of Horticulture, Clemson University (10 min)

                  Discussion with
                           Jim Gilbert, Northwoods Wholesale Nursery, Molalla, OR
                           Larry Sibley, Tollgate Gardens and Nursery, Bellevue, MI
                           John Brittain, Nolin River Nut Tree Nursery, Upton, KY
                           Lisa Brittain, Nolin River Nut Tree Nursery, Upton, KY
                           Mark Blossom, Blossom Nursery, Eureka Springs, AR
                           Annie Black, Hidden Springs Nursery, Cookeville, TN

10:45-11:00 am  Break

11:00-12:00 Noon   Regional Variety Trial Reports
  (05)                 The Pawpaw Regional Variety Trial: Background and Early Results
                                   Kirk W. Pomper*1, Desmond R. Layne2, and Neal Peterson3, 1Land
                                   Grant Program, KSU, 2Department of Horticulture, Clemson
                                   University, and 3Peterson Pawpaws, Franklin, WV. (20 min)

                         Update on the Iowa Pawpaw Regional Variety Trial
                                   Tom Wahl, Red Fern Farm, Wapello, IA. (10 min)

    (06)               Update on the Pawpaw Plantings in Michigan
                                   Mario Mandujano* and Dennis Fulbright, Botany and Plant Pathology,
                                   Michigan State University, MI (10 min)

    (07)               Corvallis Oregon Regional Pawpaw Trial in Distress
                                   Joseph D. Postman* and Kim E. Hummer, USDA National Clonal
                                   Germplasm Repository, Corvallis, Oregon. (20 min)

                         Discussion

 12:00-1:15 pm  Lunch

  1:15 -1:30 pm   Board buses

  1:30-2:30 pm   Trip to Seelbach in Louisville

 2:45-3:45 pm  Fruit Tasting and Discussion (Mezzanine Ballroom)
                        Pawpaw fruit from cultivars and PPF advanced selections
                        will be provided for tasting

  3:45-4:45 pm  Fruit Ripening and Handling (Mezzanine Ballroom)
     (08)        Ripening and Postharvest Storage of Pawpaw
                           Douglas D. Archbold1, Rumphan Koslanund1, and Kirk W. Pomper2
                            1Department of Horticulture, University of Kentucky, 2Land Grant
                            Program, KSU, (30 min)

                 Disscussion with
                          Neal Peterson, Peterson Pawpaws, Franklin, WV
                          Chris Chmiel, Intergration Acres, Albany, OH
                          And others

  4:45 –5:00 pm Break
 
 

  5:00- 6:00 pm     Cooking with Pawpaws (Grand Ballroom; 10th floor)
                               Jerry Slater, Director of Resturants, Seelbach Hilton, Lousiville, KY
                               Chefs Jim Gerhardt and Michael Cunha, The Seelbach Oakroom

  6:00 – 9:00 pm   Dinner at the Seelbach from the Chefs of the Five Diamond Restaurant,
                            the Oakroom (Grand Ballroom; 10th floor)

                      PPF award presentations starting at 7:00 pm

   (09)           The Art of Pawpaw Growing in Italy
                               Maurizio Cocchi*, Elvio Bellini, and Domenico Montanari,
                               Department of Horticulture, University of Florence, Italy
                               (15 min)

                     Show-and-tell session (20 min)

                     Poster Session (remaining time)
 (10)             Effects of Substituting Pawpaw Fruit Puree for Fat on the
                           Sensory Properties of a Plain Shortened Cake
                               Tiffany Wiese* and Melani W. Duffrin, Ohio University, Athens, OH

 (11)             Consumer Acceptance of Pawpaw (Asimina triloba) Fruit Puree as a
                            Fat- Reducing Agent in Muffins, Compared to Muffins Made
                            With Applesauce and Fat
                               Melani W. Duffrin*, David H. Holben, and
                               Matthew J. Bremner, Ohio University, Athens, OH

  (12)            Favorable Taste Ratings Reported for Several Pawpaw Products
                               Susan B. Templeton* and Martha A. Marlette, Human Nutrition
                               Research, Kentucky State University, Frankfort, KY

8:45 pm  Board Buses

9:00 pm  Return to Frankfort
 

Saturday, 9/22/01 (at the KSU Research and Demonstration Farm)

  9:30-10:00 am   Refreshments at KSU farm

10:00-10:45 am   Pawpaw Anticancer and Pesticide Products
   (13)           Pawpaw Anticancer and Pesticide Products
                           Jerry McLaughlin, Research and Development,
                           Nature’s Sunshine Products, Spanish Fork, UT

10:45-12:00 Noon   Marketing Pawpaw
                         Marketing Opportunities for Pawpaw
                                 Beth Floyd, Kentucky Department of Agriculture,
                                 Frankfort, KY (30 min)

   (14)                      Pawpaw Havesting, Processing, and Product Development in
                                Southern Ohio
                                   Chris Chmiel, Integration Acres, Albany, OH (20 min)

                       Discussion

12:00-1:00 pm  Lunch

  1:00-2:00 pm  Pawpaw Growers Roundtable
   (15)                Investigation and Evaluation of Pawpaws in North Carolina
                           Milton B. Parker, Jr., North Carolina State University, Columbus &
                          Robeson Counties, NC (20 min)

                  Discussion with
                           Roland McIntosh, Stanton, KY
                           Ilze Sillers, Versailles, KY
                           Neal Peterson, Franklin, WV
                           Chris Chmiel, Albany, OH
                           And others

   2:00-3:20 pm Submitted Talks and Additional Posters
   (16)          Comparative Reproductive Biology of two Florida Pawpaws,
                           Asimina reticulata Chapman and Asimina tetramera Small.
                             Anne C. Cox, Florida International University, Miami, FL (20 min)

    (17)        The Pawpaw Research Program at the Department of Horticulture of
                         Florence, Italy
                           Elvio Bellini and Maurizio Cocchi*, Department of
                           Horticulture, University of Florence, Italy. (20 min)

    (18)        Early Vegetative Growth Characteristics of 7 Varieties of Pawpaw
                          (Asimina triloba)
                           Anthony Bratsch*1 and Robert Bellm2
                            1Virginia Tech, Department of Horticulture, Blacksburg, VA
                            2University of Illinois Extension, Edwardsville Center, Edwardsville, IL
                           (20 min)

    (19)        Pawpaw Cultivar Development: Past and Present
                           Neal Peterson, Peterson Pawpaws, Franklin, WV. (20 min)

  3:20-3:30 pm  Break

  3:30-4:00 pm  Posters
    (20)        Evaluation of Pawpaw Extracts for Insecticidal Effects on Cucumber Beetles
                           Gary R. Cline*1, John D. Sedlacek1, John C. Snyder2, Anthony
                           Silvernail1 and Kirk W. Pomper1, 1Land Grant Program, KSU, and
                           2Dept. of  Horticulture, University of Kentucky

    (21)        DNA Fingerprinting of Pawpaw Cultivars Using the Inter Simple
                          Sequence Repeat Marker System
                           Snake C. Jones* and Kirk W. Pomper. Land Grant Program, KSU

    (22)        Identification of Inter Simple Sequence Repeat Markers That Segregate in a Simple
                         Mendelian Fashion in a Controlled Cross of Pawpaw
                           Sheri B. Crabtree*, Shawn P. Brown, and Kirk W. Pomper. Land Grant
                           Program, KSU, Frankfort KY

    (23)        Assessment of Genetic Diversity and Clonality Within Native Pawpaw Patches Using RAPDs
                           Tera M. Bonney*1, Sheri B. Crabtree1, Kirk W. Pomper1, and Robert L.
                           Geneve2. 1Land Grant Program, KSU, 2Dept. of Horticulture, University
                           of Kentucky, Lexington, KY

  4:00-5:30 pm  Orchard Tours, Fruit and Product Tasting, Grafting Demo,
                         Nursery Production Demo

  5:30-8:00 pm  Closing Dinner at the KSU Farm
 

Abstract (01)

The Kentucky State University Pawpaw Program

Kirk W. Pomper; Kentucky State University, Atwood Research Facility, Frankfort, KY 40601-2355

Kentucky State University (KSU) has had a comprehensive pawpaw [Asimina triloba (L.) Dunal] research project since 1990 with the goal of developing pawpaw into a new high-value tree fruit crop. The pawpaw program was initiated by Brett Callaway in 1990 and was expanded by Desmond Layne from 1993 to 1997. It has been under the direction of Kirk Pomper since 1998.  An overview of current KSU pawpaw extension and research activities will be discussed. Current extension activities include: 1) a web site, at http://www.pawpaw.kysu.edu, for the dissemination of information on pawpaw to scientists and growers; 2) an annual pawpaw field day, which has been presented each fall since 1998; and 3) responses to over 350 phone calls, emails, and letters each year. The objectives of the research program have been aimed at: 1) understanding the fruit ripening process; 2) conducting pawpaw variety trials; 3) optimizing seedling and clonal propagation methods; 4) enhancing pawpaw germplasm through collection and assessment; and 5) developing orchard management recommendations. Research efforts with Douglas Archbold and Robert Geneve of the University of Kentucky have attempted to understand the fruit ripening process and improve propagation methods, respectively. In 1994, KSU was approved as the USDA National Clonal Germplasm Repository for Pawpaw for Asimina spp., or gene bank; therefore, germplasm evaluation, preservation, and dissemination have been a high priority for the program. There are presently over 1700 accessions (trees) from 17 states and over 40 cultivars contained in the repository orchards. Molecular marker methodologies have been used in fingerprinting pawpaw cultivars and assessing genetic diversity across the pawpaw’s native range. Pawpaw seedlings with promising fruit characteristics have been identified in the repository collection and have been propagated for further evaluation as potential cultivars for release by KSU. The largest challenges that face the development of a commercial pawpaw industry are: developing a grower base, improving orchard establishment rates, rootstock development, improving clonal propagation methods, new cultivar development, postharvest handling of fruit, and developing an overall marketing strategy. This program is attempting to address these challenges.
 

Abstract (02)

Propagation of Pawpaw (Asimina triloba)

Cynthia Finneseth1, Sharon Kester1, Robert Geneve*1, Kirk Pomper2 and Desmond Layne3; University of Kentucky and Kentucky State University, Lexington, Kentucky 40546, 2Land-Grant Program, Atwood Research Facility, Kentucky State University, Frankfort, KY 40601-2355, 3Department of  Horticulture, Clemson University, Clemson, SC 29634-0375;

The North American pawpaw is a temperate member of the mostly tropical Annonaceae or Custard Apple family. Pawpaw has commercial value both as a small landscape tree and as an orchard fruit crop. It is also the source of several novel botanical and medicinal extracts.  Nurseries commonly propagate pawpaw from seed or chip budding. Seed propagation of pawpaw is important to the nursery industry as a source of seedlings for both ornamental and understock production. Currently, chip budding is used to propagate superior fruiting cultivars. One problem with budding is the propensity for pawpaw understocks to sucker and potentially compete with the desired cultivar. Cutting or tissue culture propagation would be a desirable way to establish pawpaw cultivars on their own roots. The objective of our research program in pawpaw is to develop propagation methods for seedling and clonal establishment of plants for commercial production.
 

Abstract (03)

Induction of Roots on Seedling Cuttings of Pawpaw Following Inoculation with Agrobacterium rhizogenes

Greg Dortch, Caula A. Beyl*, and Tomas Ayala-Silva
Department of Plant and Soil Science, Alabama A&M University, Normal, AL 35762

Agrobacterium rhizogenes, the bacterium that causes hairy root disease, was evaluated to determine its potential for inducing roots in normally recalcitrant cuttings of pawpaw (Asimina triloba (L.) Dunal).  Cuttings from three sources were collected May 11, 2001. These consisted of terminal shoot cuttings obtained from the basal portion of mature trees in a stand located in Huntsville, AL.  The second source of cuttings consisted of terminal cuttings excised from seedlings germinated in the spring.  The third source of shoots were those induced from root cuttings collected February 7, 2001 and allowed to form shoots. The response to inoculation with  either  A. rhizogenes strain MT 232 or MSU-1 was compared with the rooting response to 20,000 ppm indole-3-butyric acid.  Cuttings were evaluated on August 1, 2001. Only A. rhizogenes treatment  resulted in successful root formation.  Strain was not important as both resulted in 33% rooting. Juvenility is still a major factor influencing the success of the treatments because the induction of roots only occurred on cuttings taken from seedlings.  No roots resulted from any treatment of cuttings taken from those which were induced on root sections nor those taken from mature trees.  Treatment with Agrobacterium rhizogenes may have the potential to aid in root induction and also offer altered phenotypic characteristics in transformed root systems.
 

Abstract (04)

Container Production of Pawpaw Seedlings

Kirk W. Pomper*1, Desmond R. Layne2, and Snake C. Jones1; 1Land-Grant Program, Atwood Research Facility, Kentucky State University, Frankfort, KY 40601-2355; 2Department of Horticulture, Clemson University, Clemson, SC 29634-0375;

Pawpaw [Asimina triloba (L.) Dunal] is a native American fruit tree that has potential as a new fruit crop or for use in landscapes, but little information is available to nurseries on the production of containerized plants. In a series of experiments, the growth of pawpaw seedlings in Rootrainers was examined with various fertilization regimes, substrates, and shade levels. In an initial greenhouse experiment, growth of pawpaw seedlings was examined in three fertilization regimes and four substrates: 1) ProMix, 2) 6 pine bark:1 sand (v/v), 3) 1 sand:1 sphagnum peat moss, and 4) 4 pine bark:1 sand:1 sphagnum peat moss medium. A similar germination rate of 80% was obtained in all substrates. Weekly fertigation treatments were imposed when seedlings had 2 to 3 leaves, at 0, 50, and 100 mg/L-1 N as Peters 20N-8.6P-16.6K (Peters 20-20-20) water-soluble fertilizer plus soluble trace elements. After 140 days at the highest fertilizer rate, plant height, leaf number, and dry weight (roots, shoots, and total plant) were greater in ProMix and 1 sand:1 sphagnum peat moss than in 6 pine bark:1 sand (v/v) or 4 pine bark:1 sand:1 sphagnum peat moss.  Overall, plant biomass production was greater in ProMix than in 6 pine bark:1 sand (v/v).  In a separate greenhouse experiment, growth of seedlings was examined with Osmocote 14N-6.1P-11.5K (Osmocote 14-14-14) as the sole fertilizer source incorporated into ProMix at six treatment levels of: 0, 0.81, 2.22, 4.43, 8.86, or 17.72 kg/m-3 (0, 1.37, 3.74, 7.47, 14.93, or 29.86 lb/yard3). Early seedling growth was hastened in the 2.22 kg/m-3 (3.74 lb/yard3) treatment, but it was delayed in the17.72 kg?m-3 (29.86 lb/yard3) treatment, when compared to non-fertilized control plants. When seedlings were harvested 17 weeks after sowing, plants had the greatest shoot, root, and total dry weight with Osmocote at a rate of 2.22 kg/m-3  (3.74 lb/ yard3). The influence of shading, with 100% polypropylene shade fabric, on the growth of pawpaw seedlings in ProMix in containers was examined in the greenhouse and outdoors. Growth characteristics of pawpaw seedlings were positively influenced by low to moderate shading (28% or 51%) outdoors and low shading (33%) in the greenhouse.
 

Abstract (05)

The Pawpaw Regional Variety Trial: Background and Early Data

Kirk W. Pomper1, Desmond R. Layne2, R. Neal Peterson3, and Dwight Wolfe4;
 1Land-Grant Program, Atwood Research Facility, Kentucky State University (KSU), Frankfort, KY 40601-2355; 2Department of Horticulture, Clemson University, Clemson, SC 29634-0375; 3The Peterson Pawpaws, PO Box 1277,  Franklin, WV 26807; 4Department of  Horticulture, University of Kentucky, Research & Education Ctr, 1205 Hopkinsville Street, Princeton, KY 42445

In 1993, The PawPaw Foundation (PPF) and KSU embarked on a joint venture to evaluate many of the commercially available named pawpaw [Asimina triloba (L.) Dunal] cultivars and PPF’s advanced selections within and outside of pawpaw’s native range. Orchards for the regional variety trial (RVT), consisting of about 300 trees each, were planted in 13 different locations from Fall 1995 through Spring of 1999.  At each RVT site, 5 to 8 replicate trees of each of the 28 grafted scion varieties are being tested in a randomized complete block experimental design. Named cultivars being tested include Middletown, Mitchell, NC-1, Overleese, PA-Golden, Sunflower, Taylor, Taytwo, Wells, and Wilson. The other 18 clones to be evaluated originated in PPF orchards at the University of Maryland Experiment Stations at Wye, MD and Keedysville, MD.  Seedling trees from local native sources were planted around the perimeter as a buffer against edge effects and to allow comparisons with local germplasm. Variables being studied in the trial include climate, culture, pests, growth, flowering, yield, and fruit characteristics. Trees will be evaluated for several years for yield, year-to-year consistency, regional suitability, etc., and at the end of the trial period, regional recommendations will be made. In 1995, RVT plantings were established in KY (Princeton, KY), LA, NC, OR, and SC. In 1998, an RVT planting was established in KY (Frankfort, KY). In 1999, RVT orchards were planted in IN, IA, MI, MD, NE, NY, and OH. In the Frankfort, Kentucky planting, 95% of the trees survived since being planted in 1998. Most selections have displayed excellent vigor, in terms of tree diameter, with the exception of the selections: 5-5, 3-21, 11-5, ‘Middletown’, ‘Taytwo’, and 2-10 (Table 1). The cultivar PA-Golden had the best early fruit production as evidenced by the fact that 5 of 8 trees had fruit in 2001.  In the Princeton, Kentucky planting, only 55% of the trees planted in 1995 have survived (Table 2). The selections ‘Sunflower’, PA-Golden, Wilson, 1-23, 8-20, Middletown, NC-1, and 9-58 have shown good fruit production in 2001 on the remaining trees. With the limited data that we have collected so far in the Kentucky trials, is appears that PA-Golden has at least preformed well in the two locations, other cultivars and PPF selections show promise.
 

Abstract (06)

Growing pawpaw in Michigan

Mario Mandujano* and Dennis W. Fulbright; Department of Plant Pathology, Michigan State University, East Lansing, MI 48824-1312

Some Michigan growers have a long history working with pawpaw cultivation and some of the more common, established varieties originated from these early workers in Michigan. This rich history has long captured the interest of other Michigan nut growers who have had interests in establishing pawpaw plantations; however, many fundamental questions concerning the establishment, growth, precocity and fruit production remain unanswered. Working with the Pawpaw Foundation, we have attempted to establish in Jackson, Michigan, a variety trial with young, grafted trees.  Twenty-eight varieties were received from Northwoods Nursery (Molalla, Oregon) on 15 April 1999.  Many of the young trees were very small and had already sprouted when they arrived so they were stored in a pole barn and watered as needed until planting.  The site was prepared by placing an 8-foot deer fence around the planting site and treating the soil with methyl bromide two weeks prior to planting.  The planting plan of the Foundation was followed with trees planted 6 feet apart within rows and 18 feet apart between rows.  The trees were planted on 2 June and soon after planting it became hot and dry.  Irrigation was not available until two weeks after the trees were planted.  It was during this time that some trees were lost to the heat.  The trees were watered as needed after the initial two weeks and in the second year and each year since, the trees were fertilized with ammonium sulfate plus micronutrients. Survival of the varieties within the planting has been variable.  At this time all varieties and lines are still represented by at least one tree except 5-5 where all the trees have died, and only PA Golden is still represented by all eight trees.  Those varieties and lines with seven survivors are 2-10, 3-2-1, and Mitchell.  Those varieties or lines with five or six survivors include 4-2, 7-90, and Taylor.  Varieties with only half of the planted trees still growing include Taytwo and Wells.  The majority of the trees are represented by only two or three survivors and they include 1-7-2,1-23, 3-11, 2-54, 11-5, 9-47, 8-20, Middletown, 11-13, 8-58,1-7-1, 9-58, Overlease and Sunflower. Lines 1-68, 10-35 and Wilson only have one tree remaining of the 8 planted. Trees showing the most vigorous growth at this time are Taytwo, Mitchell, 3-21 and PA Golden.  In Michigan, we recommend establishing fruit or nut tree orchards with large, robust planting stock and the trees that started this variety trial did not meet that criteria.
 

Abstract (07)

Corvallis Oregon Regional Pawpaw Trial in Distress

Joseph D. Postman and Kim E. Hummer; National Clonal Germplasm Repository, 33447 Peoria Road, Corvallis, Oregon 97333

A pawpaw field trial was established at the National Clonal Germplasm Repository, Corvallis, Oregon in the fall of 1995. This orchard is a replicated planting of 28 cultivars, 8 trees each, grafted onto seedling rootstocks and planted in a randomized block design. The perimeter of the field is surrounded by a 1 tree wide border of Asimina triloba seedlings or ‘guard’ trees.  Two years after planting 32 trees had either failed to establish or had died after an initial healthy start. Additional trees were observed to decline each succeeding year (see Table 3). Vascular wilt-like symptoms become apparent each spring after trees have leafed out. As transpiration demand increased with warmer and drier weather, severely affected trees collapsed and died. Moderately affected trees become chlorotic with stunted new growth. Blue and black vascular discoloration was observed beneath the bark of declining trees along the lower parts of the main stem, particularly at and above the graft unions. This symptom has been described as a “blue stain”.  A canker-like bark splitting was observed near the base of many declining trees, with smaller cankers on upper scaffold branches.  By July of 1999, 25% of grafted trees had died, and two years later mortality exceeded 50%.  Seedling guard trees were unaffected until July 2000 when 6 guard trees of 76 died and 10 more were in decline.  By July of 2001 14 guard trees were dead.

Efforts to identify a pathogen associated with tree decline have so far been unsuccessful.  Samples were sent to the Oregon State University (OSU) Plant Disease Clinic in 1999. No fungi were consistently isolated from declining trees.  In May of 2000 the OSU clinic cultured several bacterial isolates from affected trees.  Assays were done using ‘Biolog™’ culture plates but no bacteria could be identified that were likely pathogens.  In summer of 2000 a number of bacteria were isolated by USDA/ARS collaborators in Corvallis, but again no likely pathogens were identified.  The search for a possible bacterial pathogen will continue, and samples are also being tested for phytoplasmas and viruses and the possibility of a nematode connection.

Initial poor establishment of selections 1-68 and 11-13 (3/8 alive in spring of 1999) and Taytwo (4/8 alive) suggest that either scions of these selections may have been diseased when they were initially grafted, or these selections are more susceptible to this tree decline than the other genotypes in the planting.  In July, 2001, after 6 years in the field, mortality was 75% or more for selections 1-7-1, 1-23, 1-68, 3-11, 3-21, 11-13, Overleese, and Taytwo.  Selections with highest survival include 9-58 (7 surviving trees) and Wilson (100% survival).  Trees have been rated for symptom severity each year since 1999.  Selections with the lowest symptom severity include 1-7-2, 2-54, 7-90, 8-58, 9-58, Mitchell, PA-Golden, Taylor and Wilson. The slow demise of the Corvallis regional variety trial may help to identify sources of resistance to this as yet unidentified disease of pawpaws.
 

Abstract (08)

Ripening and Postharvest Storage of Pawpaw

Douglas D. Archbold1, Rumphan Koslanund1, and Kirk W. Pomper2; 1Department of Horticulture, University of Kentucky, Lexington, KY 40546-0091, and 2Atwood Research Center, Kentucky State University, Frankfort, KY 40601-2335

Ripening characteristics and postharvest cold storage of pawpaw are under study to develop recommendations for harvest and shelf life extension of the fresh fruit. We have determined that pawpaw is a climacteric fruit, characterized by elevated ethylene production and respiration during ripening. Storage of both firm and slightly soft fruit at 4 ºC for at least 4 weeks kept fruit from ripening further, and moving the fruit from cold storage to room temperature allowed the process to continue. Firm, mature green fruit ripened about 2 days behind those harvested slightly soft. Fruit harvested immature failed to ripen, and ‘dropped’ fruit were over-ripe. Both internal and external firmness decreased over time starting at harvest in the same pattern although the internal tissue was softer than the external skin. The implications of these results with respect to the development of harvest and storage procedures for extending pawpaw shelf life, and the potential for manipulation of the timing and rate of ripening, will be discussed.
 

Abstract (09)

State of the Art of the Pawpaw Culture in Italy

Maurizio Cocchi*, Elvio Bellini, and Domenico Montanari; Department of Horticulture
University of Florence, Via G. Donizetti 86, Florence, Italy 50144

Several cultivation experiences and trials that have been performed in Italy during the last 20 years demonstrate that Asimina triloba is a very hard species which grows well in the soils and climate of northern Italy. For this reason Asimina triloba is an interesting tree which will be able to raise the number of fruit species that can be cultivated in Italy. This paper is a resume of the state of the art of the cultivation of Asimina triloba in Italy; in particular the authors describe the establishment of an experimental orchard in Faenza (Italy), the propagation techniques that have shown the best results, the response of this species to climatic and soil conditions of northern Italy, and the production of fruit.
 

Abstract (10)

Effects of Substituting Pawpaw Fruit Puree for Fat on the Sensory Properties of a Plain Shortened Cake

Tiffany Wiese* and Melani W. Duffrin; Ohio University, Grover Center W345, 340 Estates Drive, Athens, OH 45701

The nutrient composition and the custard like texture of the pawpaw fruit make it an excellent candidate as a fat-reducing agent in baked goods.  The objective of our study was to determine consumer acceptance (N=105) of plain shortened cake (PSC) using pawpaw fruit puree as a partial replacement for fat in the food formulation.  The cakes were prepared by replacing 25%, 50%, and 75% of the fat with pawpaw fruit puree and then compared to a control using 100% vegetable shortening.  Mean scores suggested that panelists liked all cake samples to some degree ranging from like slightly to extremely.  Panelists detected no differences between the control and the 25% fat replacement sample for all sensory attributes.  Notable preference differences were detected between the control and 25% samples and the 50% and 75% samples for the attributes of color, texture, tenderness, and overall acceptability. A preference difference was detected in flavor between the 25% and 50% samples and in aftertaste between the control and the 50% sample.  Data suggest that a 25% fat replacement with pawpaw fruit puree is acceptable in a PSC formula.  Replacing 75% of the fat with pawpaw fruit puree was acceptable only in the category of flavor.  The notable differences in color, texture, tenderness, after taste, and overall acceptability attributes may be overcome with further research and product development.  Higher levels of fat replacement may prove to be acceptable in other types of cake formulations and testing the various varieties of pawpaw fruit as a fat-replacement in baked goods is warranted.
 

Abstract (11)

Consumer Acceptance of Pawpaw (Asimina triloba) Fruit Puree as a Fat-Reducing Agent in Muffins, Compared to Muffins Made With Applesauce and Fat

Melani W. Duffrin*, David H. Holben, and Matthew J. Bremner; Ohio University, Grover Center W345, 340 Estates Drive, Athens, OH 45701

This study determined the consumer acceptance of pawpaw pulp as a fat-reducing agent in muffins as compared to muffins made with fat (regular) and muffins made with applesauce.  No significant differences were noted between the applesauce and pawpaw muffins.  Overall, the analysis of variance indicated the muffins made with pawpaw puree were equally acceptable to the other muffins for all characteristics, with the exception of appearance (color), in which regular muffins were preferred over the pawpaw variation.  The muffins made with applesauce were equally acceptable to the other muffins, with the exception of texture and overall acceptability, in which the regular muffins were preferred.  Given the efforts to domesticate the pawpaw, food science professionals should be aware of this fruit and its potential use as a fat-reducing agent.
 

Abstract (12)

Favorable Taste Ratings Reported for Several Pawpaw Products

Susan B. Templeton and Martha A. Marlette; Human Nutrition Research, Kentucky State University, Frankfort, KY 40601.

Consumed as fresh fruit, the pawpaw has a short shelf-life, only 2-3 days at room temperature and up to three weeks with refrigeration. There is commercial processing potential for pawpaw pulp in juices, ice cream, baked goods, etc. Consumer acceptability of such products needs to be investigated. One hundred and five attendees of the 2nd Annual Pawpaw Field Day held at the KSU Research Farm participated in a tasting of selected pawpaw products. Fifty-six percent of tasters were male; 58% were 41-60 years of age. Only 72% of tasters had eaten pawpaw before. Items were rated on a scale from 1 = "Liked it extremely" to 7 = "Disliked it extremely." Pawpaw ice cream was the best received item (55% of tasters liked it extremely), followed by pawpaw cake with lemon icing, liked extremely by 45%.  The pawpaw/grape juice drink was liked extremely by 31% of participants. Three alternative recipes for pawpaw butter were presented; the plain pawpaw butter was liked extremely by 26% of tasters; pawpaw butter prepared with lemon and grape juice was liked extremely by 11%, while the version prepared with orange and lemon was liked extremely by only 8%.  Two versions of pawpaw custard were presented. The custard prepared from select fruit was liked extremely by 42% of tasters, while the custard prepared from seconds was liked extremely by only 16%.  The highest percent of tasters reporting they disliked an item was 17% for pawpaw butter with orange and lemon; the lowest was 0% for pawpaw ice cream.
 

Abstract (13)

Pawpaw Anticancer and Pesticide Products

Dr. Jerry L. McLaughlin; V.P.-R&D/AQ/CSO, Nature's Sunshine Products, 1655 North Main Street, Spanish Fork, Utah 84660

For over 20 years, my research has focused on the bioactive components of pawpaw and their possible development in anticancer and pesticidal products.  The most potent components of pawpaw are a complex mixture of over 50 derivatives of C-32 and C-34 long chain fatty acids that are called the Annonaceous acetogenins.  These compounds are powerful inhibitors of mitochondrial complex I (NADH: ubiquinone oxidoreductase) and of the NADH oxidase found in the cell membranes of tumor cells.  Their net effect is reduction of ATP (adenosine triphosphate) levels and, consequently, depletion of intracellular biochemical energy.  Since resistance mechanisms often require ATP (to drive efflux pumps), the acetogenins effectively thwart resistance to pesticide and anticancer agents.  A few terminal cancer patients have consumed a tea made from powdered pawpaw twigs with some evidence of prolongation of life.  However, our current efforts are being directed toward development of "Pawpaw Special Treatment Shampoo".  Tests have shown that this shampoo is very effective against pesticide-resistant headlice.  A garden pesticide has been successfully formulated, but it is currently too expensive to be economically practical.  Genetic variations from tree to tree can cause significant variation in acetogenin content, and monthly variations in acetogenin content necessitates biomass collection only be made during a brief season.  The high costs for biomass collection and extraction currently limit the uses of these products, but we anticipate that these costs can be decreased in the future with agricultural propagation of the twigs as a new crop.  The shampoo should be on the market by the time of this conference with the initial biomass supplies coming from wild crafting of the twigs in a sustainable way that preserves the trees.
 

Abstract  (14)

Pawpaw Havesting, Processing, and Product Development in Southern Ohio

Chris Chmiel; Intergration Acres, 160 Cherry Ridge Rd, Albany, OH 45710

Chris Chmiel is a 1992 graduate of the Ohio University Specialized Studies Program.  His program, entitled "Wholistic Transition to Sustainability," was an interdisciplinary program focused around botany, economics, anthropology and the arts.  In 1995, Chris began gathering pawpaws from the hillsides of Athens County in southeast Ohio.  After researching the pawpaw industry on the Internet in 1996, Chris decided to experiment with processing the fragile fruit into a frozen pulp puree.  In January of 1997, Chris teamed up with the chefs at Casa Nueva (www.casanueva.com) for Pawpaw Night.  This well-attended event started a pawpaw craze in the Athens area.  Pawpaw cheesecake, pawpaw habanero salsa, pawpaw coladas, pawpaw ice cream and pawpaw curry made this an memorable event.  This experience of pawpaw harvesting and processing helped Chris get a job with Understory, Inc.  This company received a grant from the USDA to research non-timber forest products in the region.  Chris focused on the pawpaw and spicebush development and research.  From natural observation, Chris had noticed that the local pawpaw patches close to or in animal pastures were more productive.  He set about studying this pawpaw-growing model by capturing pollinators and recording tree fruiting characteristics.

Chris began processing pawpaws on a larger scale in 1997.  By roaming the countryside and buying from others, Chris was able to harvest almost 2,000 pounds of fruit.  Most of the fruit was processed into Pawpaw Pleasures, a two-pound package of frozen pawpaw pulp and one-pound packages of frozen pawpaw pyramids.  Some fresh fruit was also sold to a specialty fruit broker from the East Coast.  Chris now began selling Pawpaw Pleasures to local and regional restaurants and direct to customers of all sorts.  In 1998, Chris approached the village of Albany, Ohio, to see if they had an official village tree.  Since they didn't, and many on the village council liked pawpaw fruit, they decided to endorse Chris' proposal and name the pawpaw tree their official fruit.  This then quickly evolved into the first annual Albany, Ohio, Pawpaw Festival in 1999.  This event featured a pawpaw cook-off, pawpaw eating
contest and a best pawpaw contest.  Because this year's festival was very late in the season--October 10th--the pawpaw fruit crop was fairly marginal.

In 2000, Chris wrote and received a USDA Sustainable Agriculture Research and Education (SARE) Producer Grant titled "Improving Production in Native Pawpaw Patches."  This grant provided an opportunity to improve the native pawpaw patches by removing some of their competition and creating better access through thick brush.  Grafts of superior varieties were also grafted into these patches to see if this would help with pollination.  Soil samples, organic fertilizers and shade tolerant ground covers were also worked with in this grant.
Most recently, Chris has written and received another SARE producer grant to use grazing animals for managing pawpaw patches.  This is possible because of the natural pesticides in the pawpaw tree make it unpalatable to grazing animals. Chris' business is called Integration Acres.  Their product line includes Pawpaw Pleasures, as well as, three jarred pawpaw products  Pawpaw Spice Jam, Pawpaw Simmer Sauce and Pawpaw Autumn Harvest Chutney.  All these products are available online at http://www.integrationacres.com.
 

Abstract (15)

Investigation and Evaluation of Pawpaws in North Carolina

Milton B. Parker, Jr.; NC Cooperative Extension Service, 622 Wedgewood Dr,
Whiteville, NC 28472

Interest in pawpaws, Asimina triloba, began with the awarding of a SARE Producer Grant.  The grant was submitted by Charles Lowery, Ag. Extension Agent, Robeson County in 1999.  The total amount was $9,635.00 for three years.  The title is "Growing Pawpaws and Oriental Persimmons as Sustainable Crops".  The grower cooperator is Mr. Lesley Sanderson in Robeson County.  The grower wanted to investigate alternative crops that were sustainable.  Pawpaws and Oriental persimmons were selected for their few insect or disease pests.  A visit to Kentucky State University in Frankfort, Kentucky in September, 1999 resulted in information on the culture of pawpaws.
 In April 2001, 225 pawpaw trees (10 varieties) were planted.  The varieties were obtained from two nursery sources.  This planting has been established as an official regional evaluation trial.
 Several hundred seeds were provided by Kentucky State University principal investigator Dr. Kirk Pomper.  360 seedlings were germinated and are being grown in two-gallon containers.  Two year old seedlings have been distributed to several growers for evaluation.
 In September 2000 a large native pawpaw stand was located on the bluffs overlooking the Cape Fear River in Bladen County, N.C.
 Pawpaws in this native stand vary in height from 18' to over 30'.  Fruit growing individually or in clusters have been identified and tagged for future fruit selection.
 Can pawpaws be seriously considered as an alternative for tobacco in S.E. North Carolina?
 

Abstract (16)

Comparative Reproductive Biology of two Florida Pawpaws, Asimina reticulata Chapman and Asimina tetramera Small.

Anne C. Cox; Florida International University, Miami, FL 32321

Research was conducted comparing the phenology and breeding systems of two Florida endemic pawpaws, Asimina reticulata, widespread in peninsular Florida, and Asimina tetramera, a federally endangered species limited to two counties on the Atlantic Coastal Ridge.  The purpose of this study was to determine if differences contribute to the rarity of Asimina tetramera compared with A. reticulata.  The study was conducted in sand pine scrub sites, the largest populations of  A. tetramera in the two counties.  Flowering seasons differ for the two species.  Both species are hermaphroditic and strongly protogynous.  Pollination experiments show that neither species is autogamous and the primary breeding mechanism is outcrossing, although low levels of geitonogamous pollination occur in mature scrub habitats.  High levels of inbreeding depression were noted in both species at both sites but inbreeding depression was relaxed the first year post-fire.  Fruit set in mature habitats may be pollinator limited.

Insects associated with the flowers of both Asimina species were investigated in sand pine scrub habitat in southeastern Florida from 1994-1996.  The most commonly represented orders were Coleoptera (25 spp.), Lepidoptera (3 spp.) and Hymenoptera (3 spp.).  All Coleoptera were flower visitors; one species visited flowers of the two Asimina at both sites: Euphoria sepulchralis (Fabricius) (Scarabeaidae).  Eggs and larvae of Eurytides marcellus (Cramer) (Lepidoptera: Papilionidae) were observed on both species of Asimina during each yeare of the study.
 

Abstract (17)

The Pawpaw Research Program at  the Department of Horticulture of Florence ,Italy

Elvio Bellini and Maurizio Cocchi*;  Department of Horticulture, University of Florence, Via G. Donizetti 86, Florence, Italy 50144

This work will provide a brief description of the research programs that are being carried out at the Department of Horticulture of Florence:
-Seedling cultivation for genetic improvement purposes
-First results of the ongoing research on vegetative habits and fruit production of some Asimina cultivars in the Italian environment
-Future perspectives of our researches for the potential commercial exploitation of Asimina triloba for fruit production and acetogenins extraction for pest management use.
 

Abstract (18)

Early Vegetative Growth Characteristics of 7 Varieties of Pawpaw (Asimina triloba)

Anthony Bratsch1 and Robert Bellm2
1Virginia Tech, Department of Horticulture, Blacksburg, VA 24061
2University of Illinois Extension, Edwardsville Center, Edwardsville, IL 62025

For three seasons after planting, (1998-2000), early growth and development were characterized for 7 pawpaw varieties: Davis, Taylor, Rebecca’s Gold, Sunflower, Overleese, Prolific, Wells, (grafted on Pawpaw Foundation rootstock, Northwoods Nursery, Mollala, OR).  The experiment was conducted near Belleville, IL, on an Oconee Silt Loam soil. Ridged planting beds were formed 15cm high x 1.8m wide and 7.6m apart to facilitate drainage. Trees were set 5/28/98, 2.1m apart in rows, with 8 replications/variety in a RCB design. Growth parameter data included trunk cross sectional area, tree height and maximum spread; shoot and branch development, winter damage and floral initiation.

The varieties Sunflower, Prolific and Wells exhibited best total shoot growth in the planting year, from 55.7 to 61cm. All varieties lost new shoot growth to winter cold following the year of planting, with Sunflower (49.9%), Wells (44.8%) and Overleese (73.4%) losing the greatest percentage. Of 56 total trees planted, only two were lost in year 1 to cold damage. The onset of secondary branching was measured in year 2, with an average of 3.8- 4.75 bud breaks/tree. Main/lead shoot growth from these bud breaks ranged from a low of 15.7cm (Rebecca’s Gold) to a high of 44.2cm (Overleese). Overleese also exhibited the highest average shoot growth at 33.6cm, but also had the lowest bud break/tree. In all varieties, apical bud shoot growth was less than shoots originating from mid-stem and lower buds, which often became the dominant leaders.

By the end of year 3, 41% (Davis) to 62% (Taylor) of new shoots grew to lengths >30cm. Lower shoot number often, but not always, correlated with increased shoot length. Total shoot number/tree ranged from a low of 13.3 (Taylor), and 16.0 (Davis), to a high of 23.6 in Prolific, which had 52% of shoots >30cm in length. Multiple branched (3+ growing points) scaffolds formed by the end of the third year, were similar among varieties, from 3.6-4.1/tree. Cross sectional trunk area, height, and spread were greatest with Prolific, with similar size parameter trends occurring in Sunflower, Overleese and Wells. These same varieties also had the highest occurrence (3.6-6.0 buds/plant) of floral primordia present when evaluated spring of 2001, though many flower buds did not develop fully. Prolific and Wells produced the greatest number of open, viable flowers at 1.1-1.5/plant.  Though no trees were lost following the severe winter of 2000-2001, many suffered some tip dieback (2-20cm). Best hardiness was observed in Sunflower, which averaged only1.1 dead growing points/tree and most sensitive was Wells with 3.6 tips/tree lost to cold damage.
 

Abstract (19)

Pawpaw Cultivar Development: Past and Present

R. Neal Peterson, Peterson Pawpaws, PO Box 1277, Franklin, WV 26807.

Pawpaws are in the earliest stages of cultivar development. The vast majority of cultivars have been selected from the wild. Not many cultivars have been selected in cultivated settings where numerous seedlings growing side-by-side were compared. Fewer than five have been the result of deliberate crosses. The history of pawpaw cultivar development has seen the re-creation of the wheel many times, as researcher after researcher has sought superior pawpaws in the wild. This type of work has not accelerated the development of improved cultivars, but has been extremely beneficial in assembling diverse valuable germplasm. Evaluation of the 40+ extant cultivars has not been done where cultivars can be compared in standardized settings — the logical first step in a breeding program. Nor has evaluation been done of the gene pool to calculate correlations and linkages between important traits. Nor have estimates of heritabilities been computed. Great scientific work remains to be done on pawpaw genetics. The greatest accomplishments in pawpaw breeding lie ahead. Unfortunately for breeders, virtually all the germplasm collected before 1950 has been lost. My breeding efforts began by concentrating on relocating those lost collections from the early 20th century, and accessing their surviving germplasm for my work. After 18 years of growing 1400+ trees, comparing, evaluating and propagating trees, and of continually evolving in my understanding of what makes a good pawpaw, I have reached the point where I am ready to release a few of my best varieties to the public.
 

Abstract (20)

Evaluation of Pawpaw Extracts for Insecticidal Effects on Cucumber Beetles

G. R. Cline1, J.D. Sedlacek1, J. C. Snyder2, Anthony Silvernail1, and K.W. Pomper1
1Kentucky State University and 2University of Kentucky

Cucumber beetles are major insect pests of cucurbit vegetables including melons, squash, cucumbers, and pumpkins.  Pawpaw contains acetogenin compounds which are known to be toxic to other organisms.  Insecticidal effects of pawpaw extracts on cucumber beetles will be determined in a three year project funded by the Sustainable Agriculture Research and Education Program (SARE) beginning January, 2002.   One objective will be to determine direct and systemic toxic effects of pawpaw extracts on cucumber beetles in laboratory experiments.  Another objective will be to examine insecticidal effects of pawpaw extract on cucumber beetles in field studies with muskmelons.  Twigs from more than ten pawpaw genotypes were collected in May and ground.  In year one, extracts containing  actetogenin compounds will be obtained from the pawpaw twigs by sequential extraction with ethanol, chloroform, and hexane.  Relative activity of the extracts will be determined by their toxicity to brine shrimp in a bioassay.  Three pawpaw genotypes producing the most toxic extracts will be identified.    In laboratory experiments, different concentrations of extracts from these three genotypes will be applied to muskmelon leaves and evaluated for their ability to kill and/or repel cucumber beetles.  One of the three genotypes will be selected, and various concentrations of the extract from this genotype will tested as organic insecticides for cucumber beetles in field experiments with muskmelon.  Hopefully, pawpaw extract will prove effective as an organic insecticide for cucumber beetles.
 

Abstract (21)

DNA Fingerprinting of Pawpaw Cultivars Using the Inter Simple Sequence Repeat Marker System

Snake C. Jones* and Kirk W. Pomper. Land Grant Program, Kentucky State University, Atwood Research Facility, Frankfort, KY  40601-2335

Pawpaw [Asimina triloba (L.) Dunal] is a native American tree fruit that has great potential as a new commercial crop. Fruit size and quality vary considerably from tree to tree. Therefore, the reliable identification of clonally propagated superior varieties is important to nurseries that produce pawpaw cultivars and subsequently to growers who wish to establish orchards that produce high quality fruit. Kentucky State University (KSU) has served as the USDA National Clonal Germplasm Repository for Asimina spp. since 1994, as a satellite site of the repository at Corvallis, OR. The repository orchards at KSU contain more than 1700 pawpaw accessions from 16 different states, including 17 commercially available cultivars and 34 advanced selections from the PawPaw Foundation's breeding program. Our goal is to develop a reliable and reproducible DNA fingerprinting system to identify cultivars and determine genetic relationships among these geneotypes. In an effort to develop a fingerprinting system, DNA was extracted from leaf tissue of 39 pawpaw advanced selections and cultivars from the KSU repository orchards and was subjected to the Inter Simple Sequence Repeat (ISSR) methodology using the University of British Columbia microsatellite primer set #9. Four reproducible polymorphic ISSR markers have been identified using two primers, UBC857 and UBC858. Primer screening and marker selections are continuing until we identify sufficient markers to distinguish all 39 pawpaw genotypes.
 

Abstract (22)

Identification of Inter Simple Sequence Repeat Markers That Segregate in a Simple Mendelian Fashion in a Controlled Cross of Pawpaw

Sheri B. Crabtree*, Shawn P. Brown, and Kirk W. Pomper.  Kentucky State University, Atwood Research Facility, Frankfort KY 40601-2335

The pawpaw [Asimina triloba (L.) Dunal] is a tree fruit native to many areas of the southeastern and midwestern United States.  Kentucky State University is the site of the USDA National Clonal Germplasm Repository for Asmina spp.; our goal is to assess levels of genetic diversity in pawpaw across its native range and include additional unique material in our repository collection.   The objective of this study was to identify Inter Simple Sequence Repeat (ISSR) markers that segregate in a simple Mendelian fashion and use this information to assess genetic diversity of pawpaw across its native range.   Leaf samples from the 30 progeny of a controlled cross (1-7-1 x 2-54 and reciprocal) and the parents were collected, DNA was extracted, and the DNA subjected to the ISSR methodology using the University of British Colombia microsatellite primer set #9.  After chi-square analysis, three Mendelian markers at a 3:1 ratio and seven Mendelian markers at a 1:1 ratio were identified using ISSR primers. Additional ISSR primers continue to be screened to identify additional Mendelian markers.  Leaf samples from patches were collected in 11 states in the pawpaw’s native range and preliminary genetic diversity analysis using ISSR Mendelian markers is presented.
 

Abstract (23)

Assessment of Genetic Diversity and Clonality Within Native Pawpaw Patches using RAPDs

Tera M. Bonney*1, Sheri B. Crabtree1, Kirk W. Pomper1, and Robert L. Geneve2. 1Land Grant Program, Kentucky State University, Atwood Research Facility, Frankfort, KY 40601, 2Department of Horticulture, University of Kentucky, Lexington, KY 40546

Pawpaw [Asimina triloba (L.) Dunal] is a tree native to most of the eastern United States that has great potential as a new tree-fruit crop. Kentucky State University serves as the USDA National Clonal Germplasm Repository for Asimina species. The level of genetic diversity in pawpaw throughout its native range has not been fully examined. Current research efforts are directed toward assessing genetic diversity in pawpaw and improving the diversity contained in our repository collection. Pawpaw is known to reproduce both sexually and asexually, through profuse root suckering, suggesting that pawpaw patches may tend to be clonal in structure. Therefore, an investigation into the structure of genetic diversity within native patches is required in order to develop a sampling strategy for larger-scale genetic diversity studies and germplasm collection.  In order to test the ability of the RAPD methodology to identify clones, young leaf samples were collected from root suckers of seedling pawpaw trees (study #1).  Leaf samples were also collected from three native pawpaw patches in Franklin County, Kentucky (study #2).  DNA was screened with four RAPD primers, OPA-10, OPA-11, OPC-08 and OPD-20.  RAPD markers in the native patch study were identified, but reproducibility was poor.  Yet RAPD markers in the root sucker study had consistent banding patterns.  As it was often necessary to collect leaves of various ages within the native patches, the results suggest that leaf age may affect the quality of DNA extracted.  Contaminants from mature leaves may interfere with PCR amplification, therefore leaf age may be an important consideration in genetic diversity studies.
 

Figure 1. Germination percentage of pawpaw seeds after stratification at 5^oC.

(see Abstract 02; Finneseth et al.)
 

Figure 2. Germination percentage in two seed lots of pawpaw after storage.

(see Abstract 02; Finneseth et al.)
 

.Figure 3. Root formation in seedling cuttings treated with 10,000 ppm IBA.

(see Abstract 02; Finneseth et al.)

Figure 4. Shoot formation from seedling and rejuvenated explants pawpaw.

(see Abstract 02; Finneseth et al.)
 

Table 1. Summary of Tree Growth and Fruit Production in 2001 for the KSU Pawpaw Regional Variety Trial in Frankfort, Kentucky

Trees planted: March 1998
Number of trees planted: 224
(8 trees of each selection were planted)
Number of trees remaining: 211
Trunk diameter: measured April, 2001
Fruit count: taken on July 4, 2001
 

LSD 0.05 = 6.4 for diameter
(see Abstract 04; Pomper et al.)

Table 2. Summary of Fruit Production in 2001 for the KSU-UK Pawpaw Regional Variety Trial in Princeton, Kentucky

Trees planted: October, 1995
Number of trees planted: 224
(8 trees of each selection were planted)
Number of trees remaining: 122
Fruit count: July 3, 2001; for trees remaining
from the 1995 planting dates
 

*Average fruit weight based on 10 or more fruit; 100g = 3.5 oz.
(see Abstract 04; Pomper et al.)

Table 3. Survival of Pawpaws at Corvallis, Oregon Regional Variety Trial
Trees Planted in 1995 - 8 Trees per Cultivar - 76 Seedling Perimeter Guard Trees

(see Abstract 06; Postman and Hummer)

Appendix A
  Maps

Not Available

Appendix B
 Pawpaw Regional Variety Trial Field Plan

Not Available
 

Appendix C

Survival, Growth and Establishment of Grafted Pawpaws in Upstate New York

Ian A. Merwin and Rachel Byard
118 Plant Science Bldg.
Dept. of Horticulture, Cornell University, Ithaca, NY, 14853

 The Finger Lakes and Lake Ontario regions of upstate New York are at the northern limits of the original range for pawpaw (Asimina triloba) in North America.  When the national pawpaw Regional Variety Trials (RVTs) were organized in 1994, we offered to establish a test planting on a Cornell research farm in Lansing N.Y. to evaluate survival and adaptation of promising pawpaw varieties in a cool humid fruit-growing region.  In April 1999, we received and planted 224 recently grafted pawpaws from the RVT nursery in Oregon, representing 8 replications of 28 varieties.  These were planted in am orchard site that should be well suited for this species.  The glacial till soil is a gravelly silt loam in texture, with pH ranging from 5.6 to 6.2, and 8% slopes facing southwest near the deepest part of Cayuga Lake, which remains unfrozen in winter, creating a strong “lake effect” that moderates mid-winter cold temperatures.  Trickle irrigation was installed at planting, and weed control in the tree row provided with post-emergence herbicides (primarily glyphosate).

 In accordance with protocols for the RVTs, shortly after planting we installed translucent double-walled polyethylene “tree-tubes” around each pawpaw, securing them with bamboo stakes.  During a week of unusually warm days in July 1999 with afternoon temperatures around 36 ^o C (90 ^o F), most of the foliage within tubes was scorched and wilted.  Tubes were removed promptly, and the young trees grew replacement leaves.  We subsequently replaced the tree tubes with 45-cm high black polyethylene open mesh cylinders often used to protect young fruit trees from meadow vole (Microtus spp.) depredation in the northeastern U.S.  These open mesh cylinders provide a semi-shaded  environment similar to the natural understory conditions where pawpaw seedlings and root suckers thrive, and we recommend that others evaluate them as an alternative to the more expensive tree-tubes for promoting establishment of newly planted trees.

 The first two winters at our test planting site were unusually mild for the Finger Lakes region, with the lowest recorded temperatures above –16 ^o C (0 ^o F).  Despite these mild winters, there was extensive winter mortality of some pawpaw vareties, with survival rates >75% for eleven varieties, and <40% for five other varieties (Table 1). We also rated tree growth vigor, which differed substantially among varieties (P=0.02) and was positively correlated with survival rates (Table 1).  We attributed the poor survival of some varieties to the heat stress of damaged foliage as described above, and to intrinsic differences and potential weakness or incompatibility of scions and their seedling rootstocks.  We did not observe the putative “blight” that has been reported at the source nursery and some of the other RVT sites around the U.S.

By coincidence, our test planting was adjacent to a row of 50 seedling pawpaws planted in April 1998 and maintained similarly to the RVT except that open mesh guards were used instead of tree tubes.  The growth and survival of these 50 seedlings has been excellent in comparison with the RVT planting (right vs. left hand sides of Figure 1, respectively), demonstrating that site conditions were not the cause of the high mortality and low vigor observed in many of the grafted pawpaws.

 The main problem observed in our seedling pawpaw planting has been very poor fertilization or viability of flowers.  These seedling trees (and a few of our grafted clones) have flowered profusely during the past two Springs, but only a few flowers produced viable fruit.  We speculate that lack of suitable pollen vectors is the cause of this poor fruit set, because observations during bloom revealed little or no insect activity in the pawpaw flowers.  Insect activity (primarily Hymenopterans and Dipterans) in adjacent pome and stone fruit plantings has been excellent during both years of observations, so there is no lack of potential pollen vectors.  We conclude that poor establishment of grafted clonal pawpaws, and insufficient pollination or fertilization of established pawpaws may be important limitations of successful commercialization of this new fruit crop under conditions typical of upstate New York.
 
 

Table 1.  Average vigor of shoot growth and percent survival of 28 clonally
propagated pawpaw varieties in an upstate New York planting during 1999-2001.

^zRating scale: 0=No growth (dead), 5=most growth,
 

Figure 1.  View of one block (center of picture) in a Lansing, N.Y. pawpaw variety trial during its third year of growth in late June, 2001.  Each tree represents one replicate for each of the 28 varieties.  The adjacent row (right hand side of picture) of much larger seedling pawpaws was planted two years earlier, and has established very successfully, with excellent growth and negligible winter mortality.  Open black plastic mesh cylinders were placed around each grafted tree after heat stress damaged foliage within the initially used translucent plastic “tree-tubes” (as described in accompanying text).

Appendix D
Repository Accessions at the USDA National Clonal Germplasm Repository
for Asimina spp.

Principal Investigator: Dr. Kirk W. Pomper

Kentucky State University (KSU) has served as the USDA National Clonal Germplasm Repository for Asimina spp. since 1994, as a satellite site of the repository at Corvallis OR. The orchards at KSU contain more than 1700 pawpaw accessions from 66 distinct geographic regions in 16 different states, and includes 17 commercially available cultivars and 34 advanced selections from the PawPaw Foundation's breeding program. As of 2001, there were 850 pawpaw trees located in KSU’s Germplasm orchard, 340 trees in the Hybrid Orchard, 300 trees in the Regional Variety Trial Orchard, and 235 trees in the Alpha Orchard. About 200 pawpaw trees produced fruit at KSU in 2000, all trees were located in the Alpha orchard and were seedlings of 8 to 9 years old. There is also a collection of subtropical pawpaws in the KSU greenhouse representing Asimina longifolia, A. parviflora, and A. tetramera. In response to requests from the public for pawpaw germplasm, KSU is currently distributing small amounts of seed and will distribute scion wood in several years.

Current Asimina Germplasm Collection at KSU:

1. Pawpaw Trees Planted at KSU Research Farm: The orchards KSU contain more than 1700 accessions from 66 distinct geographic regions from 16 different states including

2.  Pawpaw Seedlings: Approximately 700 trees, 4 to 10 years in age, are planted in the KSU germplasm orchard from 16 states: Arkansas, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, New York, Ohio, Oklahoma, Pennsylvania, Tennessee, Virginia, and West Virginia.

3.  Grafted Pawpaw Trees: There are 435 total grafted trees that are between 2 and 4 years old in the KSU orchards. There are 215 grafted trees are part of the Pawpaw Regional Variety Trial (see Appendix B). There are 30 grafted trees in five replicated blocks each containing Taytoo, Taylor, Mitchell, NC-1, PA-Golden, and Overleese. There are 15 and 10 trees of k8-2 and k2-7, respectively, in replicated block plantings. There is a planting containing following grafted trees: 16 k8-2, 10 PA-Golden, 10 NC-1, 8 k2-7, and 6 k2-11. There are 140 additional grafted commercial cultivars and PPF advanced selections in the orchards.

4.   Pawpaw Intraspecific Hybrid Seedling Trees: 340 trees from PPF's advanced crosses.

5.  Interspecific Hybrids:  from PPF and Mr. Har Mahdeem -  seedlings from the following crosses  i. Asimina triloba x A. reticulata (55 seedlings); ii. Asimina triloba x A. obovata (3 seedlings);  and iii. Asimina triloba x A. parviflora (20 seedlings).

6.  Other Genera/Species: from PPF and Mr. Har Mahdeem -  In the field: Asimina parviflora (15 seedlings), in the greenhouse: Asimina tetramera (15 seedlings) and Asimina longifolia (5 seedlings) A. parviflora (4 seedlings)