Preliminary study on 'genomewide selection' for maize (Zea mays L.) breeding in Japanese public sectors : Estimated selection response in the first selfing cycle of single-cross progeny

Japanese public sectors are now expected to breed high-yielding silage maize varieties highly adapted to the Japanese climates in order to support the governmental policy to raise the feed self-sufficiency ratio from 26% (in 2008) to 38% by 2020. Genomewide selection (GwS) is a technique to substitute a part of phenotyping with molecular marker genotyping, and is thought to be suitable to accumulate favorable genes in many minor quantitative trait loci (QTLs) whereby yield is thought to be controlled. The purpose of this study was to use computer simulations to evaluate the potential of GwS from the viewpoint of maize breeding sections of Japanese public sectors interested in rapider yield improvement through selection at early breeding stages. It was assumed in each repeat of the simulation experiments that eight S1 (first selfing generation) candidates were selected from 1000 solely on their molecular marker information obtained from testcross investigation with GwS. The experiments indicated that (i) shorter intervals of molecular marker loci led to moderately larger selection response (SR) when the intervals were more than 20 cM, but not when they were less than 20 cM, (ii) higher heritability unexceptionally led to larger SR, and (iii) larger training population size led to slightly larger SR in most cases. The results suggest that it is important for the success of GwS to obtain high heritability in the field for testcross investigation, and that GwS will be a powerful tool for maize breeding sections of Japanese public sectors targeting rapider yield improvement.