Advanced Backcross QTL Analysis in Barley

Abstract

An advanced backcross population was constructed from H. spontaneum (accession CPI 71284-48) and the well-adapted Australian feed variety Barque as the recurrent parent. 19 BC₁F₁ individuals were each backcrossed to Barque. The subsequent 19 BC₂F₁ individuals were used to generate separate doubled haploid populations. The final combined population comprised 370 DH lines, which was reduced to 325 after selection against brittle rachis. An F₂ population was also developed from the H. spontaneum × Barque F₁. Genotyping was completed with 122 SSR markers. The F₂ derived population was genotyped with the same markers to provide an accurate linkage map, and the BC₁ and BC₂ generations were also genotyped to examine recombination of H. spontaneum linkage blocks through the backcrossing process. An analysis of the genetic structure of this population will be presented and the implications for introgression from H. spontaneum discussed. The AB-QTL population was evaluated in summer nursery rows in 2001/02, in yield trials at 2 low rainfall sites in southern Australia in 2002 and 2003. A range of agronomic and production traits, and NIR predicted malting quality traits were assessed. Markers linked to deleterious wild barley traits were identified, including head shattering, long peduncle, and free threshing ability. QTL analysis identified H. spontaneum alleles associated with improved grain yield and disease resistance. The application of AB-QTL analysis in genetic analysis and barley breeding will be discussed.