A major QTL conferring crown rot resistance in barley and its association with plant height

Abstract

Crown rot (CR) is one of the most destructive diseases of barley and wheat. Fusarium species causing CR survive in crop residue and a growing acceptance of stubble retention practices has exacerbated disease severity and yield loss. Growing resistant cultivars has long been recognised as the most effective way to reduce CR damage but these are not available in barley. In a routine screening of germplasm, a barley landrace from China gave the best CR resistance among the genotypes tested. Using a doubled haploid population derived from this landrace crossed to Franklin, we demonstrate that the CR resistance of TX9425 was conditioned by a major QTL. The QTL, designated as Qcrs.cpi-3H, was mapped near the centromere on the long arm of chromosome 3H. Its effect is highly significant, accounting for up to 63.3% of the phenotypic variation with a LOD value of 14.8. The location of Qcrs.cpi-3H was coincident with a major QTL conferring plant height (PH) and the effect of PH on CR reaction was also highly significant. When the effect of PH was accounted for by covariance analysis, the Qcrs.cpi-3H QTL remained highly significant, accounting for over 40% of the phenotypic variation. The existence of such a major QTL implies that breeding barley cultivars with enhanced CR resistance should be feasible.

Development and Validation of Markers Closely Linked to Crown Rot Resistance in Wheat and Barley

“…The barley 3H CR QTL was originally located to an interval between the DArT markers bPb-4747 and bPb-6765, which are 12.1 cM apart (Li et al, 2009). Four PCR-based primers were designed from the DNA sequences representing the four DArT markers, which are associated with the barley 3H CR QTL (Li et al, 2009).…”

“…However, a major QTL for CR resistance in barley has recently been identified from the Chinese landrace 'TX9425' which showed a moderate resistance to CR, markers linked to this QTL on the long arm of chromosome 3H count for over 60% of the phenotypic variation in resistance (Li et al, 2009). The discovery of promising QTLs for a trait of interest is an important, but primary step in developing a marker-assisted selection program for genetic improvement.…”

The homoeologous regions on long arms of group 3 chromosomes in wheat and barley harbour major crown rot resistance loci

“…TX9425 was identified from a very limited survey of 53 commercial varieties (Li et al 2009). The CR resistance of TX9425 was conditioned by a major QTL, designated Qcrs.…”

“…The answer to this question may have to wait until the fine mapping work is completed. Similarly, the possible homoeologous relationship between Qcrs.cpi-3B and the major QTL conferring CR resistance on chromosome 3H in barley (Li et al 2009) also warrants further investigation. Both 3B and 3H QTL have large effects on CR reaction and both are located on the long arms of the homoeologous group 3 chromosomes.…”

“…CR resistance of TX9425 was better than 53 commercial varieties tested (Li et al 2009). A DH population was derived from TX9425 and Franklin, an elite Australian variety highly susceptible to CR.…”