Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/1995
Publication Date: N/A
Interpretive Summary: Barley is a globally important food and feed crop for which continual improvement is justified. Crop improvement programs take much time and effort because the yield and quality traits that the breeder needs to manipulate are usually controlled by many major and minor genes. Furthermore, the genes controlling these traits can interact with each other and with the environment. This can inhibit progress in a breeding program. To shed light on this problem, the authors used detailed barley mapping information to identify regions of the barley chromosomes affecting agronomic traits. These traits were seed yield, earliness, height, lodging, kernel weight, and test weight. Most of these are considered by barley breeders when selecting for enhanced germplasm. It was found that the number of primary regions controlling these traits ranged from three to six per trait and the regions were scattered about the chromosomes. Sometimes a single chromosomal region influenced the outcome of more than one trait. This information will allow geneticists to test if marker selection can help to manipulate outcome of these traits. It may also guide barley breeders in modifying existing procedures for improved efficiency. Either way, this will be a valuable supplement to traditional barley improvement practices that should hasten the development of new, improved barley varieties.
Technical Abstract: Quantitative trait locus (QTL) main effects and QTL-by-environment (QTLxE) interactions for seven agronomic traits (grain yield, days to heading, days to maturity, plant height, lodging severity, kernel weight, and test weight) were investigated in a two-row barley (Hordeum vulgare L.) cross, Harrington/TR306. Field experiments involving 150 random doubled-haploid lines and parents were grown in 1992 and(or) 1993 at 17 sites in North America. A Harrington/TR306 base map, consisting of 127 markers on seven barley chromosomes, was constructed. Analysis of QTL was based on methods of simple and composite inverval mapping. Primary QTL inferences were made at positions where both methods gave evidence for QTL activity. The number of primary QTL estimates per trait ranged from three to six, and these explained 34% to 52% of the genetic variance. None of these QTL showed a major effect, but many showed effects that were consistent across environments. With the addition of secondary QTL inferences, 39% to 80% o the genetic variance was explained. Many of these secondary inferences showed a greater amount of QTLxE interaction. The QTL were dispersed throughout the barley genome, and some were detected in regions where QTL have been found in previous studies with barley. Eight chromosome regions contained pleiotropic loco and(or) linked clusters of loci that affected multiple traits. One region on chromosome 7 affected all traits except days to heading. This study represents an intensive effort to evaluate QTL in a very large set of environments within a population with a narrow genetic base. These results provide opportunities to test marker assisted selection, and give a glimpse of the types and distributions of QTL effects that are manipulated by plant breeders.