Investigation and validation of QTL for yield and yield components in winter barley

Abstract

The rapid development of biotechnologies in crop genetics has increased the prospects for more efficient crop improvement. In barley breeding programmes, marker assisted selection (MAS) approaches for quantitative trait loci (QTL) for yield and yield components is still developing as it requires a thorough understanding of the genetic architecture of complex traits. This project reports an investigation of QTL for yield and yield components in two-row winter barley using three QTL mapping experiments. First, a bi-parental mapping population from an elite cross identified 23 genetic factors involved in the control of complex traits, including a strong grain weight QTL on the short arm of chromosome 2H. Second, two genome wide association studies (GWAS) were used to explore the genetic diversity for agronomic traits in European variety panels used in the NUE-CROPS and the AGOUEB projects. The integration of QTL mapping results revealed clustering of significant effects as potential targets for MAS. A major QTL cluster identified on 2H suggests that the centromeric HvCEN candidate gene is strongly involved in controlling the phenology and number of grains per ear in two-row winter barley and has additional pleiotropic effects on several agronomic traits. Some QTL effects were further confirmed by a QTL validation experiment using near isogenic lines (NILs) developed from advanced breeding material alongside the mapping experiments. Most of the QTL clusters involving different yield components showed that allele effects mirrored phenotypic correlations and a few QTL clusters were identified that had unidirectional increasing effects on all traits, such as an important tillering locus on 4HL. The exploitation of comparative genomics with rice revealed that SNP haplotypes could be used for candidate gene discovery at barley QTL clusters. The complexity of the QTL clusters associated with yield and yield components highlight the challenges in identifying relevant targets for marker assisted breeding when accounting for pleiotropic effects of loci controlling phenology and correlated traits. The study provides insights into the genetic architecture of complex traits in small grain cereals and for the implementation of associated QTL in commercial barley breeding activities.