Genetic analysis of kernel weight and kernel size in wheat (Triticum aestivum L.) using unconditional and conditional QTL mapping

Abstract

Thousand kernel weight (TKW) is commonly regarded as a complex trait in wheat. Both unconditional and conditional quantitative trait locus (QTL) analyses were conducted using software QTLNetwork 2.0 in four environments to evaluate the genetic relationships between TKW and kernel size. These analyses involved a set of 182 F8:9 recombinant inbred lines derived from “Shannong01-35 × Gaocheng9411” with a genetic linkage map consisting of 503 molecular markers. Additive effects, epistatic effects, and genotype-by-environment (G × E) interactions of QTLs for TKW and kernel size were analyzed. A total of nine additive QTLs for TKW and kernel size were identified using unconditional analysis, which distributed on chromosomes 1B, 1D, 3D, 4B, 5B, and 6A. Among these, four QTLs were detected to be related to several different kernel traits. QTkw4B.1-7, QTkw5B.1-12, QTkw5B.1-17, and QTkw6A.1-29 were identified through both conditional and unconditional analyses. Seven QTLs for TKW were only identified under conditional QTL mapping. These included conditional QTLs for TKW influenced by or independent of the given kernel size traits. Twelve pairs of epistatic interaction QTLs involving 18 loci for the measured kernel traits were detected in unconditional analysis. The QTLs discovered in the present study through the combination of conditional and unconditional QTL mapping could increase the understanding of the genetic interrelationships between TKW and kernel size traits at the QTL level and provide the guiding information for breeding programs.