Pre-harvest sprouting results in significant economic loss for the grain industry around the world. Lack of adequate seed dormancy is the major reason for pre-harvest sprouting in the field under wet weather conditions. Although this trait is governed by multiple genes it is also highly heritable. A major QTL controlling both pre-harvest sprouting and seed dormancy has been identified on the long arm of barley chromosome 5H, and it explains over 70% of the phenotypic variation. Comparative genomics approaches among barley, wheat and rice were used to identify candidate gene(s) controlling seed dormancy and hence one aspect of pre-harvest sprouting. The barley seed dormancy/pre-harvest sprouting QTL was located in a region that showed good synteny with the terminal end of the long arm of rice chromosome 3. The rice DNA sequences were annotated and a gene encoding GA20-oxidase was identified as a candidate gene controlling the seed dormancy/pre-harvest sprouting QTL on 5HL. This chromosomal region also shared synteny with the telomere region of wheat chromosome 4AL, but was located outside of the QTL reported for seed dormancy in wheat. The wheat chromosome 4AL QTL region for seed dormancy was syntenic to both rice chromosome 3 and 11. In both cases, corresponding QTLs for seed dormancy have been mapped in rice.

Seed quality of 6 sweet narrow-leafed lupin (Lupinus angustifolius) cultivars was measured in 126 field trials in Western Australia over 11 years at 55 locations to determine the effect of locations (l), years (y), genotypes (g), and genotype × environment interactions on total seed alkaloids, seed oil, seed protein, seed size, and hectolitre weight. The variance component for g exceeded the sum of those for g × l, g × y, and g × l × y for all traits. The ranking of cultivars for each seed quality trait was fairly constant across years and locations. The largest variance component was l × y, which indicated that the ranking of locations for seed quality traits was unpredictable from year to year. There was a strong negative correlation between seed oil and seed protein across the 6 cultivars (r = –0.96, P < 0.01) and 126 experiments (r = –0.522, P < 0.001). Large seeds, produced at some experimental sites, were associated with high seed alkaloids and high seed oil. Seed quality traits were not associated with soil pH, latitude, or longitude of the experiments, but low pre-season rainfall was associated with higher hectolitre weight. This study indicates that it should be possible to identify genotypes with superior quality from relatively few field trials. Progress in breeding for protein and oil combined will be slowed by the strong negative genotypic correlation between the two traits.

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.

Abstract. Barley kernel discoloration (KD) leads to substantial annual loss in value through downgrading and discounting of malting barley. KD is a difficult trait to introgress into elite varieties as it is controlled by multiple genes and strongly influenced by environment and maturity. As the first step towards marker assisted selection for KD tolerance, we mapped quantitative trait loci (QTLs) controlling KD measured by grain brightness [Minolta L; (Min L)], redness (Min a), and yellowness (Min b) in 7 barley populations. One to 3 QTLs were detected for grain brightness in various populations, and one QTL could account for 5-31% of the phenotypic variation. The QTL located around the centromere region of chromosome 2H was consistently detected in 6 of the 7 populations, explaining up to 28% of the phenotypic variation. In addition, QTLs for grain brightness were most frequently identified on chromosomes 3H and 7H in various populations. Australian varieties Galleon, Chebec, and Sloop contribute an allele to increase grain brightness on chromosome 7H in 3 different populations. A major gene effect was detected for grain redness. One QTL on chromosome 4H explained 54% of the phenotypic variation in the Sloop/Halcyon population, and was associated with the blue aleurone trait. A second QTL was detected on the long arm of chromosome 2H in 3 populations, accounting for 23-47% of the phenotypic variation. The major QTLs for grain yellowness were mapped on chromosomes 2H and 5H. There were strong associations between the QTLs for heading date, grain brightness, and yellowness. The molecular markers linked with the major QTLs should be useful for marker assisted selection for KD.

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