Genetic Variability Studies in Papaya (Carica papaya L.)

Papaya is one of the most widely cultivated tropical fruit tree. Pusa Nanha x Solo, Pusa Dwarf x Coorg Honeydew, Pusa Nanha x Coorg Honeydew and Solo x Coorg Honeydew were the hybrids selected for the study. Characterization of papaya hybrids was done using Random Amplified Polymorphic DNA technique, which is quick, reliable and widely applicable. Genomic DNA was successfully isolated from four papaya hybrids using CTAB (Cetyl trimethyl ammonium bromide) method. All the 10 primers yielded amplification products with the DNA of Pusa Nanha x Coorg Honeydew. Primers OPA-03, OPA-04, OPA-12, OPB-04 and OPB-17 gave 40 scorable bands, with an average of 8.0 bands per primer. A genetic similarity matrix was constructed using the Jaccard's Coefficient Method. The pair wise similarity coefficient values varied from 0.389 to 0.714. The least similarity coefficient value (0.389) was that of Pusa Dwarf x Coorg Honeydew with Solo x Coorg Honeydew. The highest value (0.714) for similarity index was obtained for Pusa Nanha x Coorg Honeydew with Pusa Dwarf x Coorg Honeydew followed by Pusa Nanha x Coorg Honeydew-Pusa Nanha x Solo pair (0.658). Results of the trial revealed that the largest cluster in dendrogram was formed by three hybrids namely Pusa Nanha x Coorg Honeydew, Pusa Dwarf x Coorg Honeydew and Pusa Nanha x Solo. The second cluster contained only one hybrid-Solo x Coorg Honeydew. The pair wise similarity coefficient values varied from 0.389 to 0.714. The minimum similarity coefficient detected in the present study was 0.389, suggesting a genetic differentiation among the papaya hybrids.