No abstract

Recent epidemics of fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (telomorph: Gibberella zeae), in the USA and Canada have caused severe yield and quality losses in wheat (Triticum aestivum L.). Development of resistant cultivars has been difficult because of the complex inheritance of resistance and confounding environmental effects. This study was conducted to identify and map DNA markers linked to genes associated with FHB resistance. A population of 112 F5‐derived recombinant inbred (RI) wheat lines from the cross ‘Sumai 3’ (resistant)/‘Stoa’ (moderately susceptible) was evaluated in two greenhouse experiments for Type II resistance (spread within the spike). On the basis of restriction fragment length polymorphism (RFLP) marker analyses, five genomic regions were significantly (P < 0.01) associated with FHB resistance, three derived from Sumai 3 and two from Stoa. Regions on Chromosomes 3BS (from Sumai 3) and 2AL (from Stoa) were identified by interval analysis using a LOD threshold of 3.0. These two quantitative trait loci (QTL) have been assigned the gene designations QFhs.ndsu‐3B and QFhs.ndsu‐2A, respectively. Recombinant inbred lines with these two QTL had a median severity of 20.9%, compared with 36.2% for all RI lines. The best RFLP marker in the 3BS region explained 15.4% of the variation and a multiple regression model consisting of three QTL explained 29.5% of the variation. These results indicate that resistance to FHB is inherited in a quantitative manner and that marker‐assisted selection may aid the development of FHB‐resistant cultivars.

Cultivar comparisons have suggested that the 1BL/1RS wheat (Triticum aestivum L.)-rye (Secale cereale L.) chromosomal translocation enhances agronomic performance and environmental stability of wheat. This advantage has been attributed either to disease resistance genes or to unproved adaptation genes on the 1RS segment. The objective of this study was to determine the effect of 1BL/1RS without the confounding effect of cult!var background by evaluating 17 homogeneous IB, 20 heterogeneous 1B:1BL/1RS, and 22 homogeneous 1BL/ 1RS lines. The lines were randomly selected from the cross 'SiouxlandV 'Ram'. The 59 progeny lines and the two parents were tested in seven Nebraska field environments with a randomized complete-block design. Data were obtained for grain yield, components of yield, grain volume weight, anthesis date, plant height, and leaf rust infection. The 1BL/ 1RS class was 9% higher yielding than IB and heterogeneous classes. This yield advantage was attributed to increased kernel weight, which was generally expressed in lower yielding environments. Differential response to disease pressure did not explain yield differences. Within chromosome classes, differences in grain yield were attributed more to variation in number of spikes per square meter not kernel weight. The grain yield advantage of the 1BL/1RS appeared to be associated with a postanthesis stress tolerance, which resulted in increased kernel weight of the 1BL/1RS genotypes.

Previous studies with chromosome substitution lines between hard red winter wheat (Triticum aestivum L.) cultivars Cheyenne (CNN) and Wichita (WI) identified genes on chromosome 3A of WI which affect grain yield, yield components, grain volume weight, plant height, and anthesis date. This study was conducted to determine if the trait variation caused by chromosome 3A could be explained by major or minor gene segregation and if these genes are pleiotropic, linked, or independent on the chromosome. A population of recombinant inbred chromosome lines for chromosome 3A (RICLs-3A), developed between CNN and a chromosome substitution line CNN(WI3A), was evaluated in multi-location field trials in 3 yr. Our results indicate significant differences (P-< 0.05) between parental lines and among RICLs for grain yield, 1000-kernel weight, plant height, and anthesis date, but not for kernel number per spike, spike number per square meter, and grain volume weight. A 1:1 genetic ratio for anthesis date suggested the presence of a single segregating locus controlling the trait. None of the other agronomic traits could be separated into unequivocal groups and hence, major genes were not detected. This indicates that the traits were controlled either by several genes or few genes with enough environmental influence, or both, to obscure their effects. Significant correlations and possible crossover products between anthesis date, plant height, and 1000-kernel weight suggest that these traits were controlled either by linked gene(s) or by pleiotropic genes with additional genes affecting one of the traits.

The winter wheat (Triticum aestivum L.) cultivar Rawhide is heterogenous for the 1BL/1RS translocation. The 1BL/1RS translocation has been proven to increase grain yield and decrease end‐use quality in bread wheat. The objective of this research was to investigate if the excellent yield performance of Rawhide was due to higher yielding 1BL/1RS lines compensating for lower yielding 1B lines and if the acceptable quality of Rawhide was produced by higher end‐use quality 1B lines compensating for lower end‐use quality 1BL/1RS lines. To do so, 19 homogeneous 1B genotypes and 18 homogeneous 1BL/1RS genotypes were selected from Rawhide. These genotypes, three composites (Composite 1B, Composite 1BL/1RS, and Composite Total), Raw‐hide, and three check cultivars, were evaluated in four Nebraska environments for grain yield, yield components, and end‐use quality traits. No significant differences were found between chromosome classes for grain yield. The 1BL/1RS genotypes had a higher kernel weight (4%) than IB genotypes; however, the 1B genotypes had a greater number of spikes per square meter (5%). Composites were no different from Rawhide and from each other for grain yield and yield components. For end‐use quality traits, the 1BL/1RS genotypes had a higher protein content (137 mg g−1)> similar mixing time (4.8 min), and lower mixing tolerance (3.5) than 1B genotypes (132 mg g−1, 5.0 min, and 4.9, respectively). However, a mixing tolerance value of 3.5 is acceptable. In general, no differences were found among the composites and between the composites and Rawhide for quality traits. Hence, the 1BL/1RS translocation was not beneficial for yield nor was it detrimental for end‐use quality in this genetic background.