Effects of plot type on detection of quantitative-trait-locus effects in barley (Hordeum vulgare L.)

Hill plots offer advantages in testing large germplasm arrays with limited area and seed. However, the relationship of trait expression between hill vs. row plots remains in question. The development of quantitative-trait-locus (QTL) analysis offers alternative methods of testing hypotheses regarding levels of coincident gene effects in divergent plots. The objective of this study was to compare hill and row plots in terms of QTL detection, number of common QTLs and plot-type-specific QTLs for various characters in barley. Assessments were based on sets of 100 F₁-derived doubled haploid progeny from two environments of hill-plot data and two sets of multiple-environment row-plot data. Common large-effect QTLs for height, heading date, and 1000-kernel weight were detected in both plot types. Fewer QTLs were detected in the hill-plot data, with only one QTL detected for grain yield. There were no hill-plot-specific QTL effects. Hill plots appear to be best suited to highly heritable characters such as height, heading date, and 1000-kernel weight. Evaluation of grain yield is best deferred until larger experimental units can be employed.     

Variation in the pathogenicity of Erysiphe graminis D.C. F. Sp. Avenae,and its relation to the development of mildew-resistant oat cultivars

Two new physiologic races of Erysiphe graminis avenae are described, capable of attacking hitherto resistant hexaploid genotypes of Avena in the seedling stage. Two diploid forms namely A. strigosa var. glabrota and A. strigosa s.sp. hirtula provide the only sources of resistance to the races of mildew isolated in this investigation. In two cultivars, relative degrees of resistance to mildew infection in field trials have been shown to be due to resistance developing in later formed leaves of maturing plants. The importance of developing cultivars with a high degree of adult plant resistance to disease attack in the field is discussed.     

Validation of the two-gene epistatic model for vernalization response in a winter × spring barley cross

A two gene epistatic model in which a dominant “winter growth habit” allele at Vrn-H2 encodes a repressor with a corresponding binding site in a recessive vrn-H1 allele explains the vernalization response phenotypes in an array of barley germplasm. In order to validate the model genetically, we developed an F ₂ population (and F ₂-derived F ₃ families) from the cross of Hardy (winter) × Jubilant (spring). Using gene-specific primers, we determined the Vrn-H1 and Vrn-H2 allele architecture of each F ₂ plant and we measured the growth habit phenotype of each F ₂ plant via phenotyping of its F ₃ progeny under controlled environment conditions. We used a set of treatments involving plus/minus vernalization under long photoperiod and vernalization under short photoperiod. Alleles at the two loci showed expected patterns of segregation and independent assortment. Under long day conditions, the two Vrn genes were the primary determinants of heading date, regardless of the vernalization treatment. Under short photoperiod, the effects of these loci were not significant. There was incomplete dominance at Vrn-H1: heterozygotes were significantly later to head than Vrn-H1Vrn-H1 genotypes. Vrn-H2 genotypes were also significantly later to head, even when plants were vernalized. These results validate the two-gene epistatic model for vernalization response under long-day conditions. The results under short photoperiod, and the variance in flowering with vernalization, confirm that while the two Vrn genes are the primary determinants of vernalization response, they are part of a larger interactome that determines the timing of the vegetative to reproductive transition.     

Multivariate analysis of traits determining adaptation in cultivated barley

Thirty‐nine barley varieties of different origin, representing different growth types, were included in a series of experiments aimed at analysing the variability in vernalization response, photoperiod sensitivity and earliness per se and establishing the types of ecoclimatic adaptability using multivariate analysis. In the case of spring barley varieties there was no correlation between any of the three traits. For winter barleys, a negative correlation was found between photoperiod sensitivity and vernalization response and between photoperiod sensitivity and earliness per se. Vernalization response and earliness per se showed a positive correlation. Among the winter barley varieties large variations were apparent in photoperiod sensitivity, vernalization response and earliness per se, which resulted in a tremendous variation in flowering patterns and frost tolerance. Between the spring barley varieties only wider variations in photoperiod sensitivity were detected. Based on the cluster analysis, the 39 varieties could be separated into seven groups. The spring barley varieties were placed in two groups, and the winter barleys in five groups representing different adaptational types. Among these five groups two represented the two opposing extreme combinations of photoperiod sensitivity and vernalization response. The combination of large photoperiod sensitivity and no vernalization response resulted in better frost tolerance than did the combination of photoperiod insensitivity and large vernalization response.     

Effects of constant and cyclical thermal regimes on growth and feeding of juvenile cutthroat trout of variable sizes

Abstract –  The effects of constant (12, 18, and 24 °C) and cyclical (daily variation of 15–21 and 12–24 °C) thermal regimes on the growth and feeding of Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) of variable sizes were examined. Higher constant temperatures (i.e., 24 °C) and more variable daily temperatures (i.e., 12–24 °C daily cycle) negatively affected growth rates. As fish mass increased (from 0.24 to 15.52 g) the effects of different thermal regimes on mass growth became more pronounced. Following 14 days exposure to the thermal regimes, feeding rates of individual fish were assessed during acute exposure (40 min) to test temperatures of 12, 18, and 24 °C. Feeding rate was depressed during acute exposure to 24 °C, but was not significantly affected by the preceding thermal regime. Our results indicate that even brief daily exposure to higher temperatures (e.g., 24 °C) can have considerable sublethal effects on cutthroat trout, and that fish size should be considered when examining the effects of temperature.     

Effects of varying air trajectories on spatial and temporal precipitation chemistry patterns

This study was designed to determine if judicious use of synoptic data and an operational trajectory model could identify probable source regions of anthropogenic pollutants in northeastern United States precipitation and thus relate receptor measurements to emissions data without consideration of the complex intervening meteorological and chemical processes. The storm event of April 8 to 10, 1979, was selected for intensive study. Precipitation chemistry data were obtained from event samples at six MAP3S sampling sites and from hourly samples at Brookhaven National Laboratory. Concentrations of hydrogen, sulfate, nitrate and ammonium ions were used as receptor data. Some emissions data for SO_x and NO_x were obtained from the MAP3S emissions inventory. Surface and upper air meteorological data were analyzed. Backward trajectories ending at each of the sampling sites during the precipitation period were computed with the Heffter Interactive-Terminal Transport Model using selected transport layers. Results show that concentrations of pollutant species in event precipitation samples were much higher at stations at end points of trajectories passing through the Ohio River valley than at stations with other trajectories. Likewise, concentrations at Brookhaven were much higher during the end period of a trajectory through the same region than with more northerly and more southerly tracks. The model produced back trajectories consistent with synoptic flows. Concentrations of air pollutants in precipitation were roughly proportional to the number of major pollutant sources along the trajectory. These results suggest that a larger number of studies might identify more restricted source areas or even establish a quantitative relationship between source emissions along a trajectory and concentrations in precipitation at receptor sites.     

Molecular mapping of major genes and quantitative trait loci determining flowering time in response to photoperiod in barley

Two major genes (eam8 and eam10) and two quantitative trait loci (QTL) determining flowering time in barley were associated with restriction fragment length polymorphism markers. The loci eam8 and eam10 were found to map in regions of chromosomes 1HL and 3HL, respectively, already estimated from previous classical linkage analyses. While investigating doubled haploid lines of a spring habit barley mapping population, two QTL for flowering time were detected on chromosomes 1HL and 7HS, respectively, when the material was grown under long photoperiod conditions. When growing the same lines under short photoperiod, no QTL were discernible. Allelic and homoeologous relationships with flowering time loci described earlier in barley and other Triticeae species are discussed.