Genetics of grain dormancy in a white wheat

Abstract

A white-grained wheat accession, AUS1408, is a current major source of pre-harvest sprouting (PHS) tolerance in Australian breeding programs. This study has located 2 significant quantitative trait loci (QTLs) for its grain dormancy on 4AL and 5BL. Their associations with seed dormancy have been determined from population-level marker-trait associations (with 3 years of phenotype data) and confirmed by transmission/disequilibrium test on selected advanced breeding lines. The 4AL QTL was expressed in all years of testing, with phenotypic variance ranging from 5 to 15%, indicating a strong genotype × environment interaction. This QTL has been reported in wheat cultivars of diverse origin and was also found to be strongly influenced by the environment. The 5BL QTL was found to have a remarkably consistent effect on the trait at a phenotypic variance of around 10%. The successful outcome in this study was facilitated by high throughput DArT mapping, which complemented mapping with microsatellite markers for critical QTL identification. Identification of these QTLs from AUS1408 should enable sprouting tolerance derived from this source to be incorporated into advanced breeding lines, with the use of molecular markers reducing the requirement for multi-year field testing.