Genetic analysis of agronomic and malting quality QTLs in barley backcross breeding populations

Agronomic and cereal quality quantitative trait loci (QTLs) have been identified in barley and other crops using genetic markers (RFLPs). The Steptoe x Morex doubled haploid mapping population, produced by the North American Barley Genome Mapping Project (NABGMP), exemplifies these efforts. These elite varieties have been grown in different production regions of the U.S. for three decades and have distinct utilization characteristics. Several potentially useful QTLs were identified. However, few studies have explored the reliability or breeding value of the comprehensive information gleaned from these large mapping projects. Using plant genetic materials provided by the NABGMP, efficient genetic tools (STS-PCR) were developed for genetic testing of these potentially complex QTLs. Although the final goal was to achieve practically-oriented plant breeding objectives, the focus of these experiments was to test main QTL effects and examine other possible forms of gene action including epistasis, pleiotropy, and environmental interaction.; Fifty lines were derived from a backcross of Morex and DH72 using the doubled haploid line as donor parent of the Steptoe chromosome 3. The NABGMP experiments suggested that this donor chromosome carries two yield QTLs that lack pleiotropic effects on malt quality. The fifty BC{dollar}sb1{dollar} lines and parental checks were evaluated in five environments in Montana. Agronomic and grain quality traits were analyzed in all five experiments, and nine malting traits were analyzed using micromalted samples from one experiment. Headshattering and plant lodging QTL(s) reproduced one of the yield QTLs, first reported by NABGMP, with major effects on yield under certain environmental conditions. The expected backcross gains for malt quality were realized.; A gene with strong effects on barley seed germination was previously identified on chromosome 7. However, the expression of this gene was evidently dependent on genetic background effects (epistasis). The effect of this seed dormancy QTL was investigated using the aPSR128 STS-PCR marker in two Steptoe and three Morex backcross populations. The aPSR128 QTL effects were similar regardless of recurrent parent and therefore lacked epistatic control. Unlike the reciprocal effects of minor QTLs, the aPSR128 QTL showed strong effects on seed germination that persisted during after-ripening.