Genetic Diversity and Population Structure Assessed by SSR in a Peruvian Germplasm Collection of Loche Squash (Cucurbita moschata, Cucurbitaceae)

Abstract

Loche is an ancient landrace of squash from Northern Peru, notable for its vegetative re-production and lack of seeds in fruits. To date, very little is known about its genetics. Here, we used 21 simple sequence repeats to assess the genetic diversity and population structure of a collection of 100 samples of loche from three localities in Peru, and 10 samples of related species, C. pepo and C. maxima (110 accessions in total). A total 85 bands were manually scored, obtaining an average of 4.05 alleles per locus. UPGMA clustering method and principal coordinate analysis showed a clear identification between the three species of Cucurbita. Population structure analysis clustered the 110 accessions into five populations: (i) three of loche, (ii) one of C. pepo, and (iii) one of C. maxima. Genetic diversity estimation was conducted considering only the three groups (populations) of loche identified, which was 0.024 as an average. AMOVA revealed the greatest variation between populations (79.66%) and indicated that variability within populations is 20.33%. Vegetative prop-agation by means of stem cuttings and cultivation in a very restricted geographical area would ex-plain the rather low diversity of loche. This in turn would suggest that the apparent variation ob-served in fruit shape may be explained by somatic mutation and/or environmental factors.