MOLECULAR CHARACTERIZATION, HOST PLANT RESISTANCE AND EPIDEMIOLOGY OF BEAN COMMON MOSAIC VIRUS (BCMV) INFECTING COWPEA (Vigna unguiculata L. Walp)
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Date
2015-12-01
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
The etiological agent causing cowpea mosaic was identified as
Bean common mosaic virus (BCMV) on the basis of RT-PCR and electron
microscopy. An approximately 750bp PCR product corresponding to coat
protein (CP) region of virus and the presence of long flexuous filamentous
particles measuring about 952 nm in size typical to genus potyvirus were
observed under electron microscope. The characterized virus isolate
genome had 10054 nucleotides, excluding the 3’terminal poly (A) tail.
Comparison of polyprotein of virus with other potyviruses showed similar
genome organization with 9 cleavage sites resulted 10 functional
proteins.The pairwise sequence comparison of individual genes, P1
showed most divergent, but CP gene was less divergent at nucleotide and
amino acid level. A phylogenetic tree constructed based on multiple
sequence alignments of the polyprotein nucleotide and amino acid
sequences of cowpea BCMV and potyviruses, showed virus is closely
related to BCMV-HB. Whereas, Soybean variant of china (KJ807806) and
NL1 isolate (AY112735) showed 93.8 % (5’UTR) and 94.9 % (3’UTR)
homology respectively with other BCMV isolates. This virus transmitted
to different leguminous plant species and produced systemic symptoms
under greenhouse conditions. Out of 100 cowpea genotypes screened,
three genotypes viz., IC 8966, V 5 and IC 202806 showed immune
reaction in both field and greenhouse conditions. Single marker analysis
(SMA) was revealed out of 4 SSR markers linked to BCMV resistance,
M135 marker explains 28.2 % of phenotypic variation (R2) and
Polymorphic information content (PIC) value of these markers was ranged
from 0.23 to 0.37. The correlation and regression analysis showed
rainfall and minimum temperature had significant negative impact and
strong relationship with aphid population, whereas weak correlation was
observed with disease incidence. In present study aphid population had
non-significant impact and weak association with disease incidence. Path
coefficient analysis revealed most of the weather parameters exerted their
indirect contributions to the aphid population and disease incidence
except minimum temperature.
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