MOLECULAR CHARACTERIZATION OF NL-1N STRAIN OF BCMV INFECTING COMMON BEAN IN HIMACHAL PRADESH AND DEVELOPMENT OF DIAGNOSTIC KITS
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Date
2014
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CSK Himachal Pradesh Krishi Vishavavidyalaya, Palampur
Abstract
Common bean (Phaseolus vulgaris L.), locally known as “Rajmash” one of the most
widely grown grain legume crop grown around the world is vulnerable to the attack of wide range
of plant pathogens. Among these bean mosaic disease caused by Bean common mosaic virus
(BCMV), a member of family Potyviridae is most important to low yield contributing factor
because of its regular occurrence and ubiquitous seed borne nature. In India, five strains of
BCMV viz., NL-1, NL-1n, NL-4, NL-7 and NL-7n have been reported from north-western
Himalayas, of which NL-1n is widely prevalent in the entire region. The present investigations on
BCMV- NL-1n strain were undertaken to obtain complete genome sequence, relationship with
different strains and to elucidate the presence of R-genes to find out durable sources of resistance.
Typical symptoms produced were mosaic, blistering, downward leaf rolling, green vein banding,
thickening of leaves, reduction of leaf lamina and leaf deformation which were more severe on
seed borne infected plants as compared to sap inoculated. DAS-ELISA test and coat protein gene
amplification confirmed the identity of virus as BCMV and reaction pattern on International
differential set of bean varieties established the strain identity. This strain was separated from
other BCMV strains on the basis of temperature sensitivity assay as it induced temperature
insensitive necrosis on cv. Jubila that contains resistance gene (I, bc-1), thus differs from all other
strains of BCMV and BCMNV. The genome size was 10.081 kb and contains an open reading
frame that encoded a single polyprotein of 3222 amino acids which cleaved into ten proteins
typical of Potyvirus. Sequence homology, multiple alignment and phylogenetic analysis on
nucleotide and amino acid sequences showed that BCMV-NL-1n is more closely related to
BCMV-NL-1 though clustered along with other strains and isolates of BCMV. HC-Pro region
sequences based comparison among BCMV strains showed its potential for the discrimination of
different strains, however, it still needs further validation involving more number of isolates.
Under artificial inoculation conditions, 130 common bean accessions were found resistant to
strain BCMV-NL-1n in a panel of 304 accessions comprising of diverse germplasm. BCMV
resistance gene prediction based on marker assisted selection (MAS) approach, using tightly
linked SCAR markers showed the presence of three resistance genes viz., I, bc-12 and bc-3 genes
in 105, 53 and 22 common bean accessions found resistant in the present study. Five genotypes
viz., IC-43567, EC-109731, EC-116178, EC-120636 and Improved Tender Green possessed all
the three genes. The resistant sources identified against the prevalent strains can be exploited in
resistance breeding programme.
Description
Doctoral Dissertation
Keywords
##Unable to generate tags d8135.pdf, Bean, ##Unable to generate tags d8135.pdf, Plant Pathology, ##Unable to generate tags d8135.pdf, Rajmash