Current Projects

The genus Asimina is the only temperate representative of the tropical Annonaceae, or Custard Apple family, and includes eight species, Asimina triloba (L.) Dunal., A. parviflora (Michx.) Dunal., A. incana (Bartr.) Exell., A. obovata (Willd.) Nash, A. reticulata Shuttlw. ex Chapman, A. tetramera Small, A. pygmaea (Bartr.) Dunal, and A. longifolia Kral, that are indigenous to North America. The best-known species is Asimina triloba, the North American pawpaw, which has the largest edible fruit native to the United States . This species isdiploid(n=2x=18), outcrosses, and is pollinated by flies and beetles. The pawpaw fruit is very nutritious and has an almost tropical aroma and smooth, custard-like texture, with flavors reminiscent of a combination of mango, banana, and pineapple. The high fruit quality and attractive ornamental appearance give the pawpaw great potential as a commercial tree fruit or as a component in landscapes.

From about 1900 to 1960, at least 56 pawpaw cultivars were selected and named. However, fewer than 20 of these selections remain, with many being lost from cultivation through neglect, abandonment of collections, and loss of records necessary for identification. Since 1960, additional pawpaw cultivars have been selected from the wild or developed as a result of breeding efforts of hobbyists. More than 40 cultivars are currently commercially available. The loss of cultivars over the last century may have led to erosion in the genetic base of current pawpaw cultivars.

In 1994, Kentucky State University (KSU) was designated as a satellite repository for Asimina preservation in the U.S. Department of Agriculture (USDA), National Plant Germplasm System (NPGS). Germplasm evaluation, preservation, and dissemination have been a high priority at KSU since that time. The repository orchards currently contain over 1700 accessions collected from the wild in 17 states and more than 40 cultivars. One of the goals of the repository is to assess levels of genetic diversity in native populations and commercially available cultivars. Another goal is to acquire unique germplasm to include in our repository collection. Such material could be useful in future pawpaw breeding efforts. A range of molecular markers (e.g., RAPD, ISSR, SSR, etc.) are being utilized in for fingerprinting of cultivars and to evaluate genetic diversity in pawpaw at KSU.

Staff

Dr. Kirk W. Pomper, Principal Investigator
Dr. Sanjun Gu, Co-Investigator
Dr. Li Lu,  Co-Investigator
Mr. Jeremy Lowe, Co-Investigator
Ms. Sheri Crabtree, Co-Investigator
Ms. Angie Whitehouse, Technician
Ms. Lauren Collins, Undergraduate Student

Student Involvement
Undergraduate students who are interested in learning molecular biology techniques, usually those interested in biomedical careers, or are interested in projects involving plant growth and development, have received training in Horticulture Program’s laboratory. This "hands on" research experience may be taken for credit as BIO 410: Special Problems in Biology (Prerequisite: Consent of the instructor. A course in which advanced Biology students who demonstrate ability and interest in the field pursue an independent experimental or library research project. May be repeated once for credit). Students can also find research projects involving molecular genetics and information about KSU biotechnology at http://biotech.kysu.edu/ .

  Recent Publications

Duffrin M.W. and K.W. Pomper. 2006. Development of Flavor Descriptors for Pawpaw Fruit Puree: A Step Toward the Establishment of a Native Tree Fruit Industry. Family & Consumer Sciences Research Journal. 35:118-130. [PDF ]

Pomper, K.W. and D.R. Layne. 2005. The North American Pawpaw: Botany and Horticulture. Horticultural Reviews. Vol. 31:351-384. [PDF ]

Koslanund, R., D.D. Archbold, and K.W. Pomper. 2005. Pawpaw [Asimina triloba (L.)] Fruit Ripening. I. Ethylene Biosynthesis and Production. J. Amer. Soc. Hort. Sci. 130:638-642.  [PDF ]

Koslanund, R., D.D. Archbold, and K.W. Pomper. 2005. Pawpaw [Asimina triloba (L.)] Fruit Ripening. II. Activity of Selected Cell-wall Degrading Enzymes. J. Amer. Soc. Hort. Sci. 130:643-648. [PDF ]

Pomper, K.W. and M. A. Grusak. 2004. Calcium uptake and whole-plant water use influence pod calcium concentration in snap bean plants. J. Amer. Soc. Hort. Sci. 129:890-895. [PDF ]

Pomper, K.W., S.B. Crabtree, S.P. Brown, S.C. Jones, T.M. Bonney, and D.R. Layne. 2003. Assessment of genetic diversity of pawpaw varieties with inter-simple sequence repeat markers. Journal of American Society of Horticultural Science . 128:521-525.