A major QTL controlling seed dormancy and pre-harvest sprouting/grain α-amylase in two-rowed barley (Hordeum vulgare L.)

Abstract

Barley seed dormancy is controlled by multiple genes that have a strong interaction with the environment. Lack of adequate dormancy results in pre-harvest sprouting in the field under wet weather conditions. On the other hand, too much dormancy has a detrimental effect in the malting house. There is only a very 'narrow window' of dormancy for malting barley. Harrington barley, which has been a dominant malting variety in the international market and widely used in Australia barley breeding programs, is highly susceptible to pre-harvest sprouting. A doubled haploid (DH) population derived from a cross of Chebec/Harrington was used to search for molecular markers linked with seed dormancy and pre-harvest sprouting. One major quantitative trait locus (QTL) was identified to control pre-harvest sprouting measured by α-amylase activity in barley grains, and could explain >70% of the phenotypic variation. This QTL was located on chromosome 5HL and flanked by restriction fragment length polymorphism (RFLP) marker CDO506 and simple sequence repeat (SSR) marker GMS1. The SSR marker (GMS1) linked with this QTL was further validated in a Stirling/Harrington DH population. A minor QTL on chromosome 2H accounted for 8% of phenotypic variation. Two QTLs for seed dormancy were located on chromosomes 2H and 5HL. The major QTL for dormancy coincided with the QTL for pre-harvest sprouting at chromosome 5HL and explained 61% of phenotypic variation. Since the presence of the Harrington allele at this locus favoured not only pre-harvest sprouting, but also increased malting extract, diastatic power, α-amylase, and free amino acid nitrogen, development of high malting quality varieties with pre-harvest sprouting tolerance would appear to be difficult.