Genetic differentiation of Pisang Awak subvarieties and genetic variation among ‘Mali-Ong’ plantlets in Thailand using RAPD and SRAP markers

Abstract

Banana (Musa spp.) is a globally important fruit crop, with most cultivated varieties originating from hybridizations between M. acuminata (A genome) and M. balbisiana (B genome). Triploid ABB hybrids, carrying two B-genome and one A-genome sets, are valued for their stress tolerance and adaptability. In Thailand, ‘Kluai Namwa’ (Pisang Awak) is the most widely cultivated ABB cultivar, but it shows considerable phenotypic variation across subvarieties. Because morphological classification is often unreliable, molecular tools are needed to assess genetic identity and diversity. A total of 28 Thai banana genotypes, representing the AA, BB, and ABB genome groups, were analyzed using RAPD and SRAP markers. RAPD produced 109 bands with 93.6 % polymorphism, while SRAP generated 278 bands with 92.5 % polymorphism, indicating substantial genetic variation. The mean polymorphic information content was 0.22 for RAPD and 0.24 for SRAP, confirming the discriminatory power of both marker systems. UPGMA clustering separated the genotypes into two major clusters corresponding to A- and B-genome contributions, a structure further supported by PCoA. Distinctive bands, such as RAPD primer S7 (2.50 kb) and SRAP combination Me6/Em8 (0.80 kb), specifically identified ‘Kluai Hak Muk’ cooking bananas, demonstrating the potential of these markers for cultivar authentication. The genetic stability of 16 ‘Kluai Namwa Mali-Ong’ plantlets from different locations was also evaluated. Results revealed high clonal uniformity (mean similarity = 0.858) with only minor variation, likely reflecting localized cultivation practices. Overall, RAPD and SRAP markers proved effective for genome identification, diversity assessment, and clonal stability monitoring in Thai bananas. These tools will support banana breeding, germplasm conservation, and reliable authentication of high-value cultivars.