MOLECULAR CHARACTERIZATION AND DIAGNOSIS OF CUCUMBER MOSAIC VIRUS (CMV) INFECTING HOT AND BELL PEPPERS (Capsicum annuum L.)
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Date
2014-07-10
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University of Agricultural Sciences, Bengaluru
Abstract
Cucumber Mosaic Virus (CMV), which is widely distributed having a wide host
range, affects seriously both Hot and Bell peppers in Karnataka. Survey during 2013-14
in Southern Karnataka has indicated the incidence of CMV from 33.33 to 50.00 per cent
in different locations based on visual observations; where as analysis of symptomatic and
non-symptomatic samples by ELISA showed 24.00 to 40.00 per cent. Two isolates viz.,
CMV-KO and CMV-R inoculated to 27 plant species, of which seven species showed
CMV infection. Biological and molecular variability was noticed in different
geographical locations. The complete genome sequence of CMV-KO isolate was
determined by sequencing the PCR amplified fragments. The genome of CMV-KO
comprises of RNA1 with 3358nt, containing a single ORF encoding 1a protein, which is
required for viral replication with methyltransferase and helicase motifs. The RNA2 of
3045nt long contains two ORFs i.e. ORF2a and ORF2b. The ORF2a codes for replication
associated protein and ORF2b overlapping with 2a coding silencing suppressor protein.
The RNA3 of 2220nt long also contains two ORFs i.e. the ORF at the 5’, which encodes
the movement protein (3a); and the ORF at 3’, which codes for coat protein (3b); with an
intergenic region of 299nt. Sequence analysis revealed that 91-94 per cent homology with
Ia subgroup isolates and less than 75 per cent homology with subgroup II isolates. Out of
50 Capsicum genotypes screened by mechanical inoculation, 25 genotypes exhibited
immune reaction and two genotypes resistant reaction, which was confirmed by ELISA
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