Genetic analysis of barley seed dormancy for preharvest sprouting resistance and malting quality improvement

[Truncated abstract] In cereals, seed dormancy can prevent preharvest sprouting (PHS) damage in humid climates. Seed dormancy is the largest obstacle of seed germination in the malting industry when barley seeds are used as raw materials. From a molecular genetics perspective, seed dormancy has been studied as a quantitative trait, which means its formation or release is associated with genotypes, environmental conditions and possible gene by environment interactions. Australian malting barley varieties traditionally have high levels of tolerance to PHS damage. The introduction of Canadian malting varieties into Australian breeding programs has made some new malting varieties susceptible to PHS damage. Australian barley varieties Stirling and Baudin, together with Canadian barley varieties Harrington and AC Metcalfe were selected as the parents for two mapping populations Stirling/Harrington and Baudin/AC Metcalfe, to study the molecular genetics of seed dormancy. Characterisations of the Stirling/Harrington population aimed to find quantitative trait locus (QTL) of seed dormancy under different growth conditions, and identify candidate genes for a major QTL SD1 at the centromere region of 5H (5HC). Seed dormancy was measured by seed germination rates up to 192 hours (h) at an interval of 24 h. Phenotyping of seed dormancy were conducted at five sites in different years, and germination tests were carried out both in the dark and under light. The Inclusive Composite Interval Mapping (ICIM) method was employed for QTL analysis. Comparative genomics, QTL fine mapping and transcriptomic analysis were used to identify candidate genes underlying seed dormancy. The results showed that QTL locations and the effect for seed dormancy were related to the genetic background, growth conditions during grain maturity and light conditions during germination.