Genome-Wide QTL Mapping for Post-Flowering Drought Tolerance and Validation of Charcoal Rot Resistance QTLs in NILs of Sorghum
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Date
2011
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UAS Dharwad
Abstract
Two Recombinant Inbred Line Populations (RIP) derived from the cross
IS9830 x E36-1 (RIP1) and N13 x E36-1 (RIP2) were field evaluated for stay-green
and yield related traits during rabi season at two locations over three years. Parents
IS9830 and N13 were non-stay-green and E36-1 was a stay-green donor. Analysis of
variance showed positive significant association in both RIPs. A total of 530 genic
and 270 nuclear SSR markers were screened to finally genotype 40 genic, 71 nuclear
SSR markers for RIP1 and 68 genic and 70 nuclear SSR for RIP2 to construct genetic
linkage maps together with 46 anchor markers. The genetic linkage maps spanned
over 1661.1 cM and 2003.8 cM for RIP1 and RIP2, respectively. Same were used for
mapping the stable QTLs for stay-green components: stg1 (GLA15DAF) flanked by
Xtxp34-Xtxp285 on LG-A, stg2 (GLA30DAF) flanked by Xtxp205-Xtxp231 on LGE,
stg3 (GLA45DAF) flanked by Xtxp298-Xtxp324 on LG-J and dC flanked by
Xtxp6-Xiabt73 on LG-I, together accounting for 40.91 and 48.76 per cent of
phenotypic variance in RIP1 and RIP2, respectively; the positive additive effects at all
the loci was contributed by E36-1. The stable QTLs for other yield related traits
were also mapped.
The stable QTLs for component traits of charcoal rot resistance viz., cr1
(Xtxp176-Xiabt312) for lodging per cent on LG-I, cr2 (Xtxp297-Xiabt173) for
number of internodes crossed by the fungus on LG-B and cr3 (Xiabt275-Xiabt241)
for length of infection on LG-I were introgressed from E36-1 into M35-1 and SPV86
susceptible backgrounds with recurrent foreground and background screening across
BC1F1, BC2F1, BC3F1 generations and the BC3F2 progenies with various QTLs
combinations in homozygous condition pinned down. The BC3G3 near isogenic lines
(NILs) were evaluated: NILs with all the 3 QTLs recorded lodging per cent of 0.9 and
1.2 against 41.46 and 53.38 per cent incidence in controls, respectively in M35-1 and
SPV86 backgrounds. The next best NIL in both backgrounds carried cr1 and cr2.
These NILs have immediate practical utility as resistant versions.