Coat protein diversity in Bean Common Mosaic Virus and 40 elucidation of R genes in Indian landraces of Phaseolus vulgaris L

Abstract

Present investigations on bean mosaic disease caused by bean common mosaic virus (BCMV), a member of family Potyviridae were undertaken to study the molecular diversity different strains of the virus using 3 terminal region and to elucidate the presence of R-genes to find out durable sources of resistance. Symptomatology of different isolates belonging to 4 strains viz., NL-1, NL-1n, NL-7 and NL-7n consisted of mosaic, blistering, downward leaf rolling, green vein banding, thickening of leaves, reduction of leaf lamina and leaf deformation. Severity of symptoms was more in seed borne infected plants as compared to sap inoculated plants. Identity of the virus was established by DAS-ELISA and RT-PCR while strains were identified on the basis of International bean differential set. Total genomic RNA was subjected to RT-PCR generating an amplicon of ~1300 bp, eluted, cloned in pGEMT easy vector and transformed in DH5and#945; strain of E. coli. Colony PCR of positive clones confirmed the presence of insert and thus plasmid containing positive insert was isolated, lyophilized and custom sequenced. Sequences of various isolates comprised of partial NIb, complete cp and 3 UTR and were submitted in NCBI genbank. Sequence homology, multiple alignment and evolutionary divergence of 3 terminal region could not differentiate the test isolates as per the pathogenic strain groups, thereby indicating least role of this region in characterization of strains of the same virus. However, this region clearly distinguished the virus species. Similar analysis of individual components of 3 terminal region also exhibited the same pattern. Out of 347 common bean accessions, 91 accessions were found resistant to NL-1 and NL-1n strain. Prediction of resistance genes in 31 resistant accessions using tightly linked markers showed that 3 R-genes viz., I, bc-12 and bc-3 genes were present in 19, 20 and one cultivar respectively. In order to characterize the pathogenic strains of the virus under study other regions of the viral genome needs to be