MOLECULAR GENETICS OF STERILITY MOSAIC DISEASE (SMD) RESISTANCE IN PIGEONPEA (Cajanus cajan (L.) Millsp.)
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Date
2015-12-12
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
The present investigation was carried to understand the genetics of resistance to
SMD in pigeonpea. Genetic variability was studied among 70 pigeonpea genotypes for
twelve leaf morpho-anatomical traits. Analysis of variance and descriptive statistics
revealed presence of higher variability for these traits. The traits such as trichome
numbers, length on both surfaces of leaf and leaf chlorophyll content showed highest
GCV, PCV, broad sense heritability, genetic advance for direct selection. Screening of 70
genotypes against Bengaluru isolate of SMD revealed, only two cultivars (ICPL 7035 and
BRG 3) and 11 wild genotypes were resistant. Correlations study on extreme 23 resistant
and susceptible genotypes revealed significant negative association of trichome numbers
on both leaf surfaces with other leaf traits. While, significant positive correlation was
observed for trichome lengths on both surfaces of leaf with leaf thickness. The specific
leaf area, weight, trichome numbers and length on lower surface of leaf showed higher
discrimination function in relation to per cent disease incidence. Biochemical analysis
revealed all susceptible genotypes with higher mean protein content (15.96) compared to
resistant genotypes (9.06). SSAP and TRAP markers were developed based on active
retroelement CcRT8 and two R genes. SSR markers revealed BRG 3 and ICP 7035 were
the best resistant donors. The frequency distribution graph of F6 84RIL population
against SMD revealed platykurtic (Kurtosis= -0.019) and negatively skewed (Skewness=
-1.124) suggesting involvement of two or more genes for resistance. Parental
polymorphism revealed, out of 55 SSR primers 40 were polymorphic between ICP 8863
(S) × BRG 3(R). Through bulk segregant and single-marker analysis three markers viz.,
AHSSR 50150, AHSSR 34130 and AHSSR 20125 were found closely associated with SMD
resistance and explaining 21, 8 and 6 per cent of phenotypic variations. The information
generated will be very useful for resistance breeding in pigeonpea.
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