Identification of QTL for ear row number and two-ranked versus many-ranked ear in maize across four environments

Ear row number (ERN) is not only a key trait involved in maize ( Zea mays L.) evolution but also an important component directly related to grain yield. In this report, 325 recombinant inbred lines (RILs, F 6:7 ) derived from a cross between B73 with 16 rows and SICAU1212 with four rows (two-ranked with two rows per rank) were utilized to detect quantitative trait loci (QTL) associated with ERN and two-ranked versus many-ranked ears (TR). Compared to modern maize that formed approximately 8–20 rows, SICAU1212 with four rows was the extreme case. A total of 12 and 8 QTLs were associated with ERN and TR across four environments through single-environment mapping, respectively. Each QTL responsible for ERN explained 2.33–21.28 % of the phenotypic variation. And the TR variation contributed by individual TR QTL ranged from 2.09 to 12.99 %. Notably, only three QTLs, qERN2 - 1 (bin 2.02), qERN8 - 1 (bin 8.02) and qERN8 - 2 (bin 8.04), were consistently detected in each environment and by joint analysis among all environments, which simultaneously influenced ERN and TR. One of the three QTLs, qERN8 - 1 was also identified as interacting with environment. In addition, nine pairs of significant epistatic interactions (two for ERN and seven for TR) were detected among all QTLs. The epistasis between qTR2 - 1 and qTR8 - 1 was consistent in most environments. This present study may provide the understanding of the genetic basis of ERN and TR and a foundation for further fine-mapping of these common QTLs.