Cultivar-To-Wild Population Introgression in Cucurbita pepo subsp. ovifera

Abstract

Cultivar-to-wild population transgene flow occurs and can pose potential socio-ecological risks. In the USA, transgenic commercial squash cultivars [i.e., Cucurbita pepo subspecies ovifera var. ovifera] are cultivated in close proximity to cross-compatible wild squash taxa (i.e., vars. ozarkana and texana) that are native to the Americas. This association provides a unique opportunity for assessing cultivar-to-wild genetic introgression in this species. Thus, experiments were conducted using previously characterized random amplified polymorphic DNA (RAPD) to determine whether gene flow has occurred and whether alleles from putative introgression from cultivar-to-wild population exists in free-living populations. Free-living populations of C. pepo from the Ozark Plateau (southern Missouri, northwestern Arkansas, northeastern Oklahoma), Mississippi, Texas, Illinois, Kentucky, and Louisiana were examined using 21 RAPD primers (23 discriminatory bands). Banding morphotypes were useful for discriminating cultivated and wild populations. It appears that C. pepo populations in southeastern Texas and the Ozark Plateau are relatively homogeneous and did not have band morphotypes from cultivated types. Thus, these populations are most representative of var. texana (Texas) and var. ozarkana (the Ozark Plateau). The genetic compositions of accessions from some free-living populations, particularly in Illinois and Kentucky, suggest that squash, pumpkin, and ornamental gourd farming continue to be sources of genetic contamination for nearby wild populations. Thus, gene flow from transgenic cultivars to wild populations is likely, which, in turn, will lead to changes in the genetic structure of such populations.

Key Words:

• Random amplified polymorphic DNA
• gene flow
• socio-ecological risk
• introgression

Additional information

Notes on contributors

Sang-Min Chung

Sang-Min Chung was Research Associate, USDA/ARS, Vegetable Crops Research Unit, Department of Horticulture, 1575 Linden Drive, University of Wisconsin, Madison, WI 53706. Currently Sang-Min Chung is Assistant Professor, Department of Life Science, Dongguk University, Seoul 100-175, Republic of Korea.