Assessment of genetic diversity of pumpkins (Cucurbita spp.) from western Kenya using SSR molecular markers.

Pumpkins (Cucurbita spp.) are among most neglected and underutilized crops cultivated for food and medicine. The major constraint to pumpkin production is lack of genetically improved seeds. The current study was aimed at evaluating the genetic diversity of pumpkins from eight counties in western Kenya using five SSR markers. Seeds were extracted from pumpkin fruits, dried and planted on plastic trays for 4 weeks. DNA was isolated from young leaves using CTAB method and amplified. The samples were genotyped using an ABI 3730 genetic analyzer and the allelic data analyzed using Power Marker V 3.25, DARwin V 6.0.12 and GenAIEx V 6.41software. The five SSR loci were polymorphic with a total of 33 alleles and a mean PIC value of 0.534. The gene diversity and observed heterozygosity was 0.796-0.329 and 0.967-0.164, respectively. Most of genetic variations were found within and among individual samples rather than among counties, with samples of some counties having private alleles. Based on the inbreeding coefficient (F), there was outbreeding in pumpkins from Kakamega county (F = - 0.282) and inbreeding in pumpkins from Kisii, Bungoma and Nyamira counties (F = 0.500, 0.409 and 0.286 respectively). The findings of this study suggest that genetic variation and distribution of pumpkins in western Kenya was due to monocropping and intercropping farming systems, trading of pumpkins in markets and exchange of seeds among local farmers rather than geographical and climatic differences.