Alternate S1 and Diallel Cross Selection for High Yield and High Combining Ability Maize (Zea mays L.) Inbred

Abstract

                Five S2 maize families and 5 plants per family were derived from Agronomy Department, Kasetsart University program. They were selected by two cycles of S1 selection in R-49 grouped replicated honeycomb (HC) design with equilateral triangle of side 0.866 m and 40 replications. The 25
S2 plants were designated as line number 1 to 25. Selection was continued by bulk family pedigree method until S4 lines were obtained. Simultaneously, remnant S2 seeds were diallel crossed within each family set and the top intra-family hybrid (F1 C0) of each set was self pollinated to obtain S1s which subsequently diallel crossed to obtain intra-family hybrids of cycle-1 (F1C1). However, only S1s of the top F1 C0 of the first top 3 family sets were used. Moreover, the top F1 C0 of each set were diallel crossed and testcrossed to their corresponding S4 sister lines to obtain inter family and intra-family testcross hybrids, respectively. All types of hybrids and S4 lines were evaluated for their yielding ability and combining ability at the National Corn and Sorghum Research Center, Thailand.

                Intra-family hybrids of the cycle-0 and cycle-1 were at par with the common check for grain yield. However, the yield of one intra-family testcross hybrid of the second set of cycle-0 was significantly higher than that of the common check, while two inter-family hybrids of cycle-0 were relatively high yield but not significant from the single cross, Agron2029. Yield of most S4 lines from pedigree selection were relatively high and could be used for commercial seed production. The methods fitted to the additive gene effect model and effectively identified high yielding early generation hybrids which could be used as source of either recycled single cross hybrids or modified double cross hybrids. It is expected that this
research will provide a guide line for appropriate selection intensities for inbred line development in maize. The method is the alternate S1-diallel cross selection for high yield and high combining ability inbreds in highly selected materials for the production of hybrids which adapt to wide ranges of plant densities.