VALIDATION OF QTLs IMPLICATED IN RESISTANCE TO SORGHUM DOWNY MILDEW AND COMBINING ABILITY STUDIES IN MAIZE (Zea mays L.)
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Date
2010-06-15
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University of Agricultural Sciences, Bangalore
Abstract
An investigation was carried out to validate the QTLs conferring resistance to sorghum
downy mildew (SDM) and to understand the combining ability, nature of gene action, magnitude of heterosis for yield and other important traits of newly developed inbred lines in maize (Zea mays L.) available at Zonal Agricultural Research Station, V.C. Farm, Mandya. SDM is caused by Peronosclerospora sorghi and the resistance is of polygenic nature. This study was conducted to validate QTLs reported previously, in the F2 population derived from the cross MAI 105 x CM 500. The F2 progeny consisting of 159 plants, along with the parental lines were evaluated in the disease screening nursery at Mandya during rabi 2009. The parental screening with eight SSR primers reported to be linked to resistance revealed that the SSR markers bnlgl893, phi078, phi 102 and mmc0241 failed to differentiate parents where as the other markers nc013, bnlgll54, phi073 and bnlgl702 clearly differentiated the parents, but these markers failed to differentiate resistant and susceptible bulks and the banding pattern on
individual plants used for constituting bulks was not consistent with the phenotypes and this
could be due to a combination of various factors.
Combining ability analysis using line x tester design was conducted in inbred lines by
crossing thirty four lines with five testers. The ratio of sea / gca variance revealed that there was
preponderance of non additive gene action in the expression of all the traits under study. Inbred
lines viz., MAI 708, MAI 109, MAI 111, MAI 121, Cymt 3 and Cymt 30 were found to be good
general combiners for yield and yield attributing characters. Tester CM 500 was high combiner
for grain yield. Among the crosses, MAI 109 X MAI 105, MAI 109 X CM 202, Cymt 30 X NAI
137, Cymt 3 X SKV 50 and Cymt 3 X CM 202 exhibited highest significant sea effects and high
heterosis over checks for yield and yield attributing traits.
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