Combining Ability Analysis of RILs Developed from a YML32 × Q11 Cross for Grain Yield and Resistance to Gray Leaf Spot
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The development of resistant lines and hybrids is an economical way to control disease and improve yield stability. The objectives of this study were (i) to investigate if differences in resistance to gray leaf spot (GLS, caused by Cercospora zeina) exist among recombinant inbred lines (RILs) with and without the quantitative trait locus encompassing the resistance-carrying GZ204/IDP5 DNA segment (RDNAS) and to determine its effect on grain yield, and (ii) to determine general combining ability and specific combining ability effects for grain yield and GLS scores (GLSS). Four RILs (three with RDNAS [RL1_1, RL1_2, and RL2_1] and one without RDNAS [RL2_2]) were developed via marker-assisted selection from a cross between YML32 and Q11-an elite line susceptible to GLS. The four RILs and the susceptible parent (Q11) were crossed as testers with 13 maize (Zea mays L.) lines of known heterotic groups (Suwan1, Reid, and non-Reid). The three RDNAS-carrying RILs showed reduced GLSS and improved grain yield stability, but grain yield itself was not significantly increased. These three RILs also showed negative general combining ability effects for GLSS. RL2_1 was the best line for improving GLS resistance. The RILs possessing the RDNAS in crosses with lines from the Suwan1 heterotic group had lower GLSS than those from Reid and non-Reid heterotic groups, suggesting that resistance genes or quantitative trait loci, in addition to RDNAS, might be present in Suwan1.
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