Combining Ability of Maize Inbred Lines under Water Stress Conditions

Abstract

Cultivating drought-tolerant maize is an effective strategy for reducing yield losses caused by dry spells during the growing season. The study aims to evaluate the combining ability of maize inbred lines under drought conditions to develop drought-tolerant hybrids with relatively high yields. The first experiment was conducted using a factorial mating design, producing 63 hybrids from 16 inbred lines (7 lines in Group 1 and 9 lines in Group 2). These hybrids were subsequently evaluated together with elite hybrid varieties and commercial varieties, totaling 70 varieties, with DOA Nakhon Sawan 5 used as the check variety. The test was performed under conditions of withholding water from before flowering for 2 weeks until reaching 1 month, then watering as usual. The second experiment was done using a 7 × 10 alpha lattice design with two replications during the 2024 dry season. The result showed that five hybrids, namely Nei502007 x Nei542006, Nei502007 x Nei542018, TF7 x Nei542020, Nei502007 x Nei532003, and TF7 x Nei542006, gave yields of 1,146, 1,046, 1,037, 1,034, and 1,026 kg/rai, respectively. These yields were higher than that of the check variety, DOA Nakhon Sawan 5 (749 kg/rai), but were not significantly different from those of the commercial hybrid DK7212C and CP389, which yielded 1,066 and 1,059 kg/rai, respectively. In addition, four inbred lines with high positive general combining ability and values significant difference from zero, Nei502007, Nei532003, Nei542006, and Nei542020, were selected as testers to evaluate yield potential for new hybrid development. These inbred lines will be used for development of drought-tolerant maize varieties in the future.