Neil Howes

Genetics of grain dormancy in a white wheat

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.

Selection of breeders' lines for wheat quality: Australian innovations

ABSTRACT Early-generation selection for quality traits is one of the keys to achieving greater efficiency in wheat breeding. We are pursuing this at complementary levels, using both protein and DNA markers to achieve breeding targets. Capillary electrophoresis is being used to provide efficient identification of marker proteins, particularly quantitative analysis of specific high- and low-molecular-weight glutenin subunits. Computer programs have been developed to provide automatic interpretation of the results, facilitating their use in breeding. Immunoassays have also been devised to contribute the specificity and speed of antibodies to breeding. Assays now in use include tests for α-amylase (due to sprouting or the late-maturity-amylase trait), rye translocation lines (1A/1R and 1B/1R), and the isoforms of granule-bound starch synthase (to segregate degrees of starch waxiness). In addition, proteomics is being used to identify a wider range of useful quality-marking polypeptides. For DNA analysis, a whole-genome genotyping system (DArT™) has been developed, using microarray technology. Some 200 polymorphic markers have been used to discriminate between a large range of Australian cultivars and advanced lines. This technology is providing improved selection for wheat and barley breeders for agronomic and disease traits, as well as aspects of grain quality.