QTL IDENTIFICATION AND MARKER ASSISTED SELECTION FOR SORGHUM DOWNY MILDEW RESISTANCE IN MAIZE (Zea mays L.)
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Date
2014-01-10
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University of Agricultural Sciences GKVK, Bangalore
Abstract
Sorghum downy mildew (SDM) of maize caused by
Peronosclerospora sorghi (Weston and Uppal) is a serious disease in
Southern India. An attempt was made to identify resistant sources to
develop mapping population and identification of QTLs implicated in
resistance to SDM. A set of 50 inbreds were evaluated for their reaction to
SDM at Mandya during kharif and rabi 2010 and genotypes CML226,
SKV50 and EC598475 were resistant. The magnitude of variation revealed
by PCV and GCV was high for SDM. QTLs mediating resistance were
mapped using 128 SSRs and 191 SNPs in 200 F2:3progenies derived from
the cross CML153 (susceptible) X CML226 (resistant). A total of 319
polymorphic markers were assigned to ten chromosomes of maize with
threshold LOD of 3 covering 2065.3cM with average interval length
between markers of 6.47cM. About 90% of genome was located within
10cM distance to the nearest marker. Eight putative QTLs were detected
for resistance to SDM using composite interval mapping. Despite seasonal
differences, three consensus QTLs on chromosome bin locations 2.09,
3.04 and 6.05 had a major effect in combined analysis and explained total
of 55. 9% of the phenotypic variation. Co-localization of these QTLs in bins
2.09 and 3.04 was observed with major QTLs for different biotic stresses.
This indicates common dependency on the .expression of SDM and
different biotic stress resistance. From the F3 progenies; 108 resistant
. plants wre advanced to F6 employing Marker Assisted Selection. In F4 and
Fs generations, the progenies were selected and advanced based on
flanking SSR markers (Phil01049, Umc1030, umc1388 and umc1462) of
three major QTLs identified on chromosomes 2, 3 and 6. In F6 generation,
33 resistant lines were identified in the SDM screening nursery at ZARS,
V.C. Farm, Mandya during Kharif-2013, thereby proving the utility of
major QTLs identified in the study.
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