Genetic dissection of ear-related traits using immortalized F2 population in maize

Ear-related traits are often selection targets for maize improvement. This study used an immortalized F2 (IF2) population to elucidate the genetic basis of ear-related traits. Twelve ear-related traits (namely, row number (RN), kernel number per row (KNPR), ear length (EL), ear diameter (ED), ten-kernel thickness (TKT), ear weight (EW), cob diameter (CD), kernel length (KL), kernel width (KW), grain weight per ear (GW), 100-kernel weight (HKW), and grain yield per plot (GY)), were collected from the IF2 population. The ear-related traits were comprised of 265 crosses from 516 individuals of the recombinant inbred lines (RILs) under two separated environments in 2017 and 2018, respectively. Quantitative trait loci (QTL) analyses identified 165 ear traits related QTLs, which explained phenotypic variation ranging from 0.1% to 12.66%. Among the 165 QTLs, 19 underlying nine ear-related traits (CD, ED, GY, RN, TKT, HKW, KL, GW, and KNPR) were identified across multiple environments and recognized as reliable QTLs. Furthermore, 44.85% of the total QTLs showed an overdominance effect, and 12.72% showed a dominance effect. Additionally, we found 35 genomic regions exhibiting pleiotropic effects across the whole maize genome, and 17 heterotic loci (HL) for RN, EL, ED and EW were identified. The results provide insights into genetic components of ear-related traits and enhance the understanding of the genetic basis of heterosis in maize.