INHERITANCE OF SLOW-RUSTING RESISTANCE TO LEAF RUST IN WHEAT

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 rive 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 x 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 bv either plant height or plant maturity.