Race‐specific resistance of wheat (Triticum aestivum L. emend. Thell.) to leaf rust (Puccinia recondita f. sp. tritici) is often short‐lived. Slow‐rusting resistance has been reported to be a more durable type of resistance. To exploit the advantages of this durability, genetic analysis of slow rusting is essential. Inheritance of slow‐rusting resistance to leaf rust was studied in F6 families of spring wheat in two field experiments. The F6 families resulted from two diallel crosses involving one fast‐rusting and either five or two slow‐rusting wheat genotypes. Parents and progenies were evaluated in replicated field trials under epidemics initiated by artificial inoculation. The area under disease progress curve (AUDPC) was used to measure rust severity over time. Significant differences in AUDPC were observed among crosses and among progeny within crosses. Mean AUDPC values of crosses ranged from 16 to 538. Predominantly additive genetic variance for slow rusting was detected, but additive × additive genetic variance also was present. Narrow‐sense heritability varied from 45 to 92%, depending on the cross. Correlation coefficients between slow rusting and plant maturity were negative and low. Positive but low correlation coefficients between plant height and slow rusting were observed. Results indicated that early‐generation selection for slow‐rusting resistance to leaf rust in wheat should be effective, and would not be significantly influenced by either plant height or plant maturity.

Cereal Chem. 77(2):230-236Twenty-seven durum wheat genotypes originating from different geographical areas, all expressing LMW-2 at Glu-B3, and five bread wheats were evaluated for flour mixing properties, dough physical characteristics, and baking performance. Gluten polymeric composition was studied using size-exclusion HPLC of unreduced flour protein extracts. As a group, durum wheats had poorer baking quality than bread wheats in spite of higher protein and total polymer concentrations. Durum wheats exhibited weaker gluten characteristics, which could generally be attributed to a reduced proportion of SDS-unextractable polymer, and produced less extensible doughs than did bread wheats. However, substantial variation in breadmaking quality attributes was observed among durum genotypes.Better baking performance was generally associated with greater dough extensibility and protein content, but not with gluten strength related parameters. Extensibility did not correlate with gluten strength or SE-HPLC parameters. Genotypes expressing high molecular weight glutenin subunits (HMW-GS) 6+8 exhibited better overall breadmaking quality compared with those expressing HMW-GS 7+8 or 20. Whereas differences between genotypes expressing HMW-GS 6+8 and those carrying HMW-GS 7+8 could only be attributed to variations in extensibility, the generally inferior baking performance of the HMW-GS 20 group relative to the HMW-GS 6+8 group could be attributed to both weaker and less extensible gluten characteristics.

Forty F 6 lines, the two parental lines, and a susceptible check cultivar of wheat (Triticum aestivum L.) were inoculated in the young flag leaf stage with leaf rust (Puccinia recondita f.sp. tritici) and evaluated for latent period, receptivity, and uredinium size in a greenhouse experiment. Genotypic (rg) and phenotypic (rp) correlations between latent period and uredinium size were -0.81 and -0.62, respectively. A negative correlation (rg = -0.50, rp = -0.41) was found between latent period and receptivity and a positive correlation (rg = 0.28, rp = 0.26) between uredinium size and receptivity was found. Area under the disease progress curve (AUDPC) and final rust severity (FRS) obtained from a subsequent field study with common entries were negatively correlated with latent period and positively correlated with uredinium size. Correlations of receptivity with both AUDPC and FRS were not significant. The distributions of F 6 family mean uredinia size and latent period were continuous between slow rusting and fast rusting parents: however, the distribution for receptivity was discrete. Narrow-sense heritability estimates were 63%, 57%, and 47% for uredinium size, latent period, and receptivity, respectively. Estimates of the minimum number of effective factors were three for latent period and three or four for the uredinium size and receptivity. The components are controlled by closely linked genes or due to pleotropic effects of the same gene.Abbeviations: AUDPC -Area under the disease progress curve, FRS -Final rust severity.

The winter wheat (Triticum aestivum L.) producing region of the U.S. Pacific Northwest (PNW) is subject to periods of water deficit during sowing and grain filling. Improving the genetic adaptation of wheat to drought stress represents one of the main objectives of regional breeding programs. One biochemical response to dehydrative stress is the accumulation of a family of proteins called dehydrins, which are believed to protect membranes and macromolecules against denaturation. Although previous studies demonstrated the accumulation of dehydrins in drought‐stressed wheat, little was known about the relation of dehydrin expression to acquisition of drought tolerance in specific varieties adapted to the PNW. We characterized dehydrin accumulation during the exposure of seven cultivars (‘Connie’, ‘Gene’, ‘TAM105’, ‘Rod’, ‘Hiller’, ‘Rhode’, and ‘Stephens’) to progressive drought stress in four separate experiments. The objective was to identify differences in the nature or timing of dehydrin expression in these cultivars and to learn whether dehydrin expression was associated with the acquisition of stress tolerance during seedling development. Expression of a 24‐kDa dehydrin was observed in Connie, TAM105, and Gene after 4 d of stress and at subsequent sampling dates while no dehydrins were detected in nonstress control plants. Dehydrin expression was significantly delayed in the remaining cultivars. The presence of this dehydrin was related to acquisition of drought tolerance characterized by a greater maintenance of shoot dry matter production in Connie, TAM105, and Gene. Although the role of these proteins remains unknown, their association with stress tolerance suggests that dehydrins might be used to improve the adaptation to drought.

A preliminary study was made involving the nature of inheritance of Al toxicity in wheat. The difference in tolerance between the susceptible and moderately resistant varieties tested appears to be controlled by a single dominant gene.