GENETIC DIVERSITY IN FOUR SPECIES OF MEXICAN SQUASH (Cucurbita spp.)

Abstract

Accessions of four Mexican species of squash (Curcubita argyrosperma Huber, C. pepo L., C. moschata (Duchesne ex Lam.) Duchesne ex Poiret, and C. ficifolia Bouché) from Central-Southern México were analyzed to determine genetic diversity among and within species, and to obtain the corresponding genetic fingerprints. RAPD (Random Amplified Polymorphic DNA) molecular markers were used. Sixty primers were tested, and 185 loci were studied. Percentage of polymorphic loci among species was 90.6 %. Low genetic variability was detected within species, accounting for 14.7 % of polymorphism in C. argyrosperma, 14 % in C. ficifolia, 20.8 % in C. pepo and 37 % in C. moschata. Genetic flow was present at low levels (Nm = 0.14), indicating the occurrence of less than one migrant per generation among populations of species. The coefficient of genetic differentiation among population (Gst = 0.77) showed
that the four species are highly differentiated. RAPD markers grouped the species into four large groups, each species corresponding to one group. C. argyrosperma and C. moschata were the most related species with an identity coefficient of 0.79. C. pepo was related to C. argyrosperma and C. moschata with identity coefficients of 0.63 and 0.69, respectively. C. ficifolia was the most distant species.