Studies on the genetic polymorphism of courgetti (Cucurbita pepo L.) accessions by ISSR analysis

Abstract

Purpose. Identify genetic polymorphism and divergence of C. pepo L. varieties and hybrids of different geographical origin using ISSR markers.Methods. ISSR analysis was used to evaluate the genetic polymorphism of 29 C. pepo L. varieties and hybrids of different origin. The similarity coefficient between the investigated courgetti accessions was calculated by the Nei – Li’s formula. Calculating coefficients of similarity and phylogenetic tree construction was performed with the Phylip-3.69 software package. The cluster analysis was performed by the Neighbor-joining method. The validity of the accessions grouping into clusters was tested by bootstrap analysis.Results. The use of 13 primers in the intermicrosatellite regions revealed 129 loci of courgetti DNA, among them 109 were polymorphic, 20 were monomorphic, 11 were unique to certain accessions. Electrophoregrams of the amplification products of the investigated accessions differed in the number and size of the amplicons. High DNA polymorphism of the investigated courgetti accessions was found, which ranged from 62,5% (primer UBC 810) to 100% (primers UBC 2, UBC 3, and UBC 846). The level of molecular genetic polymorphism of courgetti accessions varied from 55,8 to 63,6% in the 'Rimini' and 'Eight Ball' hybrids correspondingly. Low genetic divergence was determined between the C. pepo L. specimens, the Nei – Li similarity coefficient was 0,0005–0,0092. Using the cluster analysis, courgetti accessions were grouped into two clusters. The main criterion for clustering was the level of genetic divergence. The geographical origin of the accessions did not affect the peculiarities of their grouping.Conclusions. The results of the study of courgetti accessions of different geographical origin using ISSR analysis revealed high genetic polymorphism and little genetic divergence between the experimental accessions. Unique DNA fragments have been identified and can be used for the certification of relevant samples, as well as for the development of other molecular genetic markers. The obtained information may be useful for optimizing the courgetti breeding process and for further studies in the molecular genetics of this culture.