Microsatellite fingerprinting and analysis of intra-population divergence in morphotaxonomic traits in a large Musa (AAB genome) germplasm

Plantain (Musa spp. AAB genome) is a major staple with an incredibly enormous potential for domestic and global trade that can serve as a vital source of income for many developing countries. The fruits are extraordinarily significant, providing an important and cheap source of dietary energy, vitamins, and several essential minerals to millions of consumers within the humid and sub-humid tropics. As molecular characterization is important for sustainable exploitation of crops, the extent of genetic and agro-morphological differentiation in a large Musa population of 109 accessions was evaluated using 10 microsatellite (SSR) markers and 14 morphotaxonomic descriptors, as a basis for selection of high yielding varieties. Measurement of DNA diversity delineated the plantains into 2 major groups and 8 distinct clusters, each with several sub-clusters. There was equally a very wide diversity detected in morphotaxonomic traits including pseudostem girth, number of bunches per plant, number of hands per bunch, number of fruits per bunch, number of fruits per hand, bunch weight, length of plant cycle, and flowering to harvest interval, which varied significantly (p < 0.05) amongst the accessions. Selection based on cluster analysis using standard morphological data also delineated the cultivars into 8 distinct clusters, with one of these containing samples that were most distant to all others and exhibited a 'double bunching' phenotype at fruiting; tacitly implying the presence of significant variability that symbolizes an excellent opportunity to bring about genetic improvement through selection of improved varieties. Principal component analysis based on morphotaxonomic traits revealed 7 attributes which contributed to 79.95% of total variation that was quite similar to the 71.87% detected using microsatellite fingerprinting. Correlation analysis between selected agronomic traits demonstrated that pseudostem girth was positively associated with bunch weight, number of hands per bunch, number of fruits per bunch, number of fruits per hand, and flowering to harvest interval across all accessions. Collectively, the data in this study suggest that plantain accessions with very unique traits expressing paramount horticultural significance are available within the diverse germplasm evaluated and are currently being collected for future breeding purposes to broaden the genetic base of this important crop.