Diversity analysis in Indian cooking bananas (Musa, ABB) through morphotaxonomic and molecular characterisation.

Abstract

Improvement of ABB bananas is one of the breeding objectives of the National Research Centre for Banana (NRCB), India. India is one of the main centres of origin and domestication of Musa balbisiana. The ability of the species to introgress naturally with Musa acuminata has contributed to the wide diversity of B and B-rich genomes (like ABB) in India. The NRCB field genebank has a vast collection of 125 cooking banana accessions, dominated by the Monthan and Bluggoe subgroups. Phylogenetic studies offer the potential for unveiling the diversity available in the cooking bananas for exploitation in genetic improvement programmes. In the present study, the ABB germplasm was characterised through morphotaxonomic traits and molecular markers, with AA and BB genomes included as reference groups. The data were subjected to Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) using NTSYS (Rohlf, 1998). Out of 125 accessions characterised morphotaxonomically, 71 accessions were distinct, whilst the rest (54) were synonyms. Forty-eight accessions, suspected to be synonyms based on morphotaxonomic characterisation, were characterised using 36 pairs of microsatellite markers. In both systems, cluster analysis resulted in two major clusters. Cluster 1 comprised AA accessions and cluster 2 included BB and ABB accessions. Though Monthan and Bluggoe are the major subgroups, the current study also resulted in another subgroup called Bontha, which clustered along with Monthan at 40% similarity. The estimated Cophenetic correlation coefficients were significant (0.98) in both molecular and morphotaxonomic characterisation, indicating a good fit of the dendrogram with the similarity matrices produced. The two-dimensional scatter plot obtained as a result of PCA also confirmed the clustering patterns elucidated by HCA. The phylogenetic relationships derived in the present study complemented with fertility studies facilitate identification of diverse parents, useful for the development of superior hybrids. These data also facilitated the elimination of synonyms during the establishment of a comprehensive core collection at NRCB.