The use of genetic markers for detecting DNA polymorphism, genotype identification and phylogenetic relationships among banana cultivars

Abstract

Genetic variations and relationships among 21 commercially important banana cultivars of South India were evaluated using 50 decamer RAPD primers and 12 ISSR primers. The primers were selected after a preliminary screening of several such primers for their ability to produce clear and reproducible patterns of multiple bands. The analyses resulted in the amplification of totally 641 bands of 200-3100bp, of which 382 bands were polymorphic, corresponding to nearly 60% genetic diversity. The RAPD and ISSR surveys between pairs of 21 cultivars revealed 60.15% and 56.73% of polymorphic bands, respectively. A strong linear relationship was observed between the Resolving power (Rp) of the primer and its ability to distinguish genotypes. Based on these data, a genetic similarity matrix was established and a dendrogram for each set of primers was developed by UPGMA. The genetic similarity coefficients in RAPD analysis ranged from 0.3177 to 0.7818 and in ISSR analysis from 0.1800 to 0.8462. A fingerprinting key was generated where the presence/absence of specific RAPD/ISSR bands were recorded for each cultivar. The presence of a specific RAPD (OPC-5(800)) band was observed for an endemic cultivar--Nanjanagudu Rasabale (NR). The study resulted in the identification and molecular classification of South Indian banana cultivars of which Robusta and Williams are global and others have either limited geographical distribution or purely endemic to South India. A group of eight cultivars was identified that are highly distinct from one another. The members of this group may be useful for generating 2X and 4X breeding populations for further use in breeding secondary triploid hybrids.