A comparative survey of genetic diversity among a set of Caricaceae accessions using microsatellite markers

A preliminary survey of genetic diversity among 34 commercially popular Carica papaya cultivars from India and abroad, 6 accessions of Vasconcellea species and 1 accession of Jacaratia spinosa, was done using 20 simple sequence repeat (SSR) markers. The SSR profiles were used to find out total number of alleles, null and rare alleles, Polymorphism Information Content (PIC) values and to calculate similarity matrix using Jaccard's coefficient. The subsequent dendrogram was made by unweighted pair-group method of arithmetic average (UPGMA) and neighbor-joining method. Based on these parameters a comparison was made between the Indian papaya cultivars and the rest of the accessions. All the markers showed polymorphism and a total of 140 alleles were identified. The average number of alleles was 7 alleles/locus. Categorically the Vasconcellea and Jacaratia species had 54 alleles, the 7 non-Indian Carica papaya accessions had 70 and the 27 Indian accessions had 102 alleles. The average PIC value was 0.735 per marker. A total of 37 rare alleles were identified. Jacaratia spinosa had 17 rare alleles. Nineteen null alleles were detected among the Carica papaya accessions. A Carica papaya accession from South Africa, Hortus Gold had 5 null alleles. The genetic similarity among the accessions ranged from 7% to 67%. In the dendrogram, the Vasconcellea and Jacaratia spinosa accessions separated as a distinct cluster from the rest of the Carica papaya accessions. The study indicated that the accessions of Indian Carica papaya cultivars included in this survey are genetically more diverse than the non-Indian Carica papaya cultivars.