Role of B-genome in evolution of Banana (Musa spp) cultivars and spread of Banana Streak Virus (BSV)

Abstract

Plantains and bananas originated from intra and inter specific hybridization between two wild species. M. acuminata Colla. and M. balbisiana Colla., which contributed A and B genomes respectively. B genome is very important as it is associated with resistance to pests, diseases and drought tolerance, determination of the starch type. Although integration of BSV DNA into the host’s genome is not required for viral replication, the genome of banana contains numerous endogenous BSV (eBSV) sequences of banana B genome. With this background investigation on “Role of B-genome in evolution of Banana (Musa spp) cultivars and spread of Banana Streak Virus (BSV)” was carried out. Results revealed that Musa F1 hybrids displayed a wide segregation in all selected morphological characteristics, floral characters such as male bud shape, bract apex shape, wax on the bract, compound tepal basic color, stigma color, lobe color of compound tepal etc showed highest segregation compared to other morphological traits. Sample of 50 accessions of natural hybrids representing various genome combinations were tested with the SSR marker (Ma_gSS8) amplified an allele of 733 bp in the accessions with exclusively AA genome, 652 bp in accessions having only the BB genome and both the alleles in the interspecific hybrids, which reveled the use of this marker in distinguishing the genomes. And using degenerate conserved primer specific for RT/RNase H regions of ORF-III of BSV amplified eBSVs from two parents i.e. Calcutta-4 and Beeheekela, 20 from out of 82 F1 hybrids and in few natural hybrids, Multiple alignments of these sequences with already known sequences of eBSV present in the NCBI data base indicated that natural hybrid (BB), male parent Beeheekela (BB) and F1 hybrids (AAXBB) sequences showed 91.32-96.4% nucleotide identity, indicating the BSV genome is passed on from male parent to the hybrids, whereas female parent (Calcutta-4) eBSV has nucleotide homology of only 63% which indicates this eBSV of AA genome has not passed on to the hybrids, however this has 90.3% homology with natural hybrid of ABB group indicating the fact that in nature it might be transferred or integrated in to the BB genome.