Quantitative trait locus (QTL) main effects and QTL by environment (QTL × E) 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 (Hordeura vulgare L.) cross, Harrington/TR306. A 127-point base map was constructed from markers (mostly RFLP) scored in 146 random double-haploid (DH) lines from the Harrington/TR306 cross. Field experiments involving the two parents and 145 random DH lines were grown in 1992 and/or 1993 at 17 locations in North America. Analysis of QTL was based on simple and composite interval mapping. Primary QTL were declared at positions where both methods gave evidence for QTL. The number of primary QTL ranged from three to six per trait, collectively explaining 34 to 52% of the genetic variance. None of these primary QTL showed major effects, but many showed effects that were consistent across environments. The addition of secondary QTL gave models that explained 39 to 80% of the genetic variance. The QTL were dispersed throughout the barley genome and some were detected in regions where QTL have been found in previous studies. Eight chromosome regions contained pleiotropic loci and/or linked clusters of loci that affected multiple traits. One region on chromosome 7 affected all traits except days to heading. This study was an intensive effort to evaluate QTL in a narrow-base population grown in a large set of environments. The results reveal the types and distributions of QTL effects manipulated by plant breeders and provide opportunities for future testing of marker-assisted selection. M OLECULAR MAPS of plant genomes, used in conjunction with phenotypic measurements, can provide information about chromosome regions that affect quantitative traits. Although knowing whether such regions represent individual quantitative trait loci (QTL)

Malting is an important end use of barley (Hordeum vulgare L.). The suitability of barley for malting depends on numerous quality characteristics, all of which are affected by genetic and environmental variation and many of which are inter-related. Here, our objective was to use genome mapping to improve knowledge about the genetic basis for variation and covariation in grain and malt quality characteristics. Kernel plumpness, kernel weight, grain protein, fine-grind extract, fine-coarse difference, soluble protein, extract p-glucan, extract viscosity, diastatic power, and a-amylase activity were measured on grain produced in six field environments, from parents and doubledhaploid progeny of a two-row barley cross, 'Harrington'/'TRJ06'. Quantitative trait loci and QTL x environment interactions were detected by means of 127 mapped markers and two methods of QTL analysis: simple interval mapping (81M) and simplified composite interval mapping (sCIM). Each trait was affected by two to four primary QTL (those detected using both 81M and sCIM) and similar numbers of secondary QTL (those detected by only one of 81M or sCIM). Together, these QTL explained 21 to 67% of the phenotypic variance per trait. The numbers, effects, and relative positions of these QTL were in concordance with the quantitative trait distributions and with correlations among traits. All chromosomes, except chromosome 2, contained regions with at least one important QTL. Several genomic regions affected multiple traits. Most QTL interacted with environment, but many showed effects consistent enough that they might serve as targets for marker-assisted selection. There was little similarity in the QTL positions detected here and those detected previously for the same traits in crosses representing other germ plasm groups. MALTINGis an important end use of barley. Barley grain suitable for malting normally commands a premium price. Malted barley (malt) is used predominantly for brewing beer, but some is used for distilling and in food products. The malting process involves steeping the grain in water, followed by germination in a controlled environment. The resulting "green malt" is then dried by kilning at gradually increasing temperatures. During steeping and germination, hydrolytic enzymes are synthesized and/or activated. Some of these enzymes are involved in the breakdown of endosperm cell walls. This breakdown, which opens up the cells to attack by starch-and protein-degrading enzymes, is often

Effective breeding for disease resistance relies on a thorough understanding of host-by-pathogen relations. Achieving such understanding can be difficult and challenging, particularly for large data sets with complex host genotype-by-pathogen strain interactions. This paper presents a biplot approach that facilitates visual analysis of host-by-pathogen data. A biplot displays both host genotypes and pathogen isolates in a single scatter plot; each genotype or isolate is displayed as a point defined by its scores on the first two principal components derived from subjecting genotype- or strain-centered data to singular value decomposition. From a biplot, clusters of host genotypes and clusters of pathogen strains can be simultaneously visualized. Moreover, the basis for genotype and strain classifications, i.e., interactions between individual genotypes and strains, can be visualized at the same time. A biplot based on genotype-centered data and that based on strain-centered data are appropriate for visual evaluation of susceptibility/resistance of genotypes and virulence/avirulence of strains, respectively. Biplot analysis of genotype-by-strain is illustrated with published response scores of 13 barley line groups to 8 net blotch isolate groups.

traits. Comparisons between reduced (≈40 g kg Ϫ1 ) and normal (≈110 g kg Ϫ1 ) palmitic acid families showed a There has been a major effort to produce soybean [Glycine max significant decrease in seed yield (Rebetzke et al., 1998; (L.) Merr.] lines with modified fatty acid profiles in order to improve quality and develop new uses for soybean oil. Utilization of the lines Ndzana et al., 1994) and total oil content (Ndzana et depends on their agronomic traits and stability of the fatty acid pro-al., 1994) in the reduced palmitic acid lines. Lundeen files in diverse environments. The objectives of this study were to et al. (1987) reported that there were significant differ-(i) evaluate the influence of years and locations on the fatty acid ences between the means of the elevated and normal composition of soybean genotypes with unique fatty acid profiles, (ii) stearic acid lines for maturity, lodging, plant height, determine which fatty acids and fatty acid profiles are the most stable, and protein and oil contents, however, it was of little and (iii) evaluate agronomic and seed quality traits of mutant soybean agronomic importance.lines. Genotypes were evaluated over three years (1996, 1997, and Other studies have shown that mutant alleles do not 1998) at four locations in Southern Ontario, Canada. Year effects have a significant effect on agronomic traits. Horejsi et had the largest impact on all fatty acid levels. Location effects were al. (1994) used backcrossing to develop reduced palmitic significant only for oleic and linolenic acids. Genotype ϫ year interaction effect was significant for all fatty acids whereas genotype ϫ acid families with seed yields similar to the recurrent location and genotype ϫ year ϫ location interaction effects were parent. Lundeen et al. (1987) and Hartmann et al. (1997) significant only for oleic, linoleic, and linolenic acids. Mutants withreported that there were lines with elevated stearic acid reduced or elevated palmitic, elevated oleic, or reduced linolenic acid contents that were not significantly different in seed concentrations exhibited average or higher stability than lines with yield than the highest yielding line in the population. normal levels of these fatty acids. Therefore, these lines may be suit-Increasing oleic acid content in soybean by recurrent able for growing in a wide range of environments. Maturity, plant selection was correlated with increases in seed size and height, lodging, seed size, and seed quality were significantly different a reduction in time to maturity, but seed yield, seed oil, between mutants and cultivars. Seed yield was significantly reduced and protein content seemed to be unaffected (Carver in mutants compared to cultivars. et al., 1986). Wilcox et al. (1993) and McClure (1999) both indicated that the fan allele was not associated with agronomic traits desired in commercial soybean T he end use of soybean [Glycine max (L.) Merr.]

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