Identification of large-effect QTL for kernel row number has potential for maize yield improvement

The kernel row number (KRN) per ear is an important component of maize (Zea mays L.) yield. In this study, a line with six kernel rows, MT-6, was used to investigate the genetic basis of KRN by quantitative trait locus (QTL) mapping. MT-6 was derived from a maize inbred line Mo17 and a teosinte entry X26-4 (Zea mays ssp. mexicana), with 23 % of its genome being homologous to X26-4. An MT-6/B73 F₂ segregating population consisting of 266 individuals was genotyped using 192 molecular markers spread evenly across the genome. The same F₂ population, together with its F_2:3 population, was phenotyped for KRN in three environments. Five individual QTL for KRN, including three substantially consistent major QTL detected in all environments, were identified on chromosomes 1, 2, 3, 4, and 5, respectively. These QTL accounted for 39.5–65.0 % of the KRN variation in these populations. Additionally, one pair of epistatic interaction between two loci with additive effects was detected and accounted for about 3 % of KRN variation. These results demonstrate that a few major QTL could substantially affect the evolution of maize KRNs and therefore provide valuable information for our understanding of the mechanism of KRN and the improvement in maize grain yield by molecular breeding.