ABSTRACT. Kernel number per ear (KNE) is one of the most important yield-related agronomic traits in maize (Zea mays). To clarify its genetic basis, we made a quantitative trait locus (QTL) analysis of KNE in a recombinant inbred line population derived from lines Mo17 and Huangzao4, under two nitrogen (N) regimes. Seven QTLs, on chromosomes 4, 6 and 9, were mapped under the high N regime, which explained phenotypic variation ranging from 5.03 to 15.49%. Under the low N regime, three QTLs were located on chromosomes 6 and 9, which accounted for phenotypic variation ranging from 8.54 to 12.21%. These QTLs had different mapping intervals to their nearest markers, ranging from 0 to 16.5 cM. According to the chromosome positions and genetic effects of these QTLs, only seven QTLs for KNE were identified in our experiment, out of which three were found under both N regimes, on chromosomes 6 (one) and 9 (two); the other four were mapped only under the high N regime, on chromosomes 4 (three) and 6 (one). This information could be useful for developing marker-assisted selection in maize-breeding projects.

Grain rate (GR) is a very important trait in maize (Zea mays L.) breeding program related to yield. To realize its genetic basis, a recombinant inbred line (RIL) population and different nitrogen (N) regimes were used to map the quantitative trait loci (QTLs) for GR in maize. As a result, two QTLs were identified under high N regime and could explain a total of 14.84% of phenotypic variance. Due to additive effect, the QTL on chromosome 6 could decrease 0.029 of GR, while the QTL on chromosome 9 could increase 0.0203 of GR. Under low N regime, one QTL was mapped on chromosome 6 and could account for 9.52% of phenotypic variance, and owning to additive effect, the QTL could make GR decrease by 0.0234. The result in comparison with previous studies showed that the three QTLs in this present study were new quantitative loci associated with GR in maize. These results were beneficial for understanding the genetic basis of GR in maize.