Characterization and inheritance of adult plant stem rust resistance in durum wheat

Few durable resistance genes have provided long-term effective control of stem rust (casual pathogen Puccinia graminis Pers. f. sp. tritici Eriks and E. Henn.), a destructive disease of wheat (Triticum ssp.). The most prominent gene, Sr2, derived from the tetraploid wheat, 'Yaroslav Emmer' (Triticum turgidum L.), contributes to the protection of many hexaploid cultivars worldwide. Additional durable resistance genes are necessary to reduce the reliance on the continued effectiveness of Sr2 alone, or in gene combinations, To find alternative sources of durable resistance, the adult plant reactions of four durum (T. turgidum) cultivars, 'Glossy Huguenot', 'Marouani', 'Bansi) Strain 168', and 'Russian 1364-3' to a group of P. graminis tritici pathotypes were studied. Glossy Huguenot and Marouani displayed adult plant resistance alone, while the other cultivars were susceptible. The adult plant resistance significantly reduced the number of stem rust pustules per unit area and delayed the onset of disease, compared with susceptible controls, Genetic analysis performed on F-1 plants, F-2-derived families, and F-3 plants from segregating F-2-derived families showed that adult plant resistance was determined by dominant alleles at a single locus in each parent. All progeny from the cross of the resistant parents were adult plant resistant, suggesting that the allele is probably common to each parent. The apparent continued effectiveness of the Glossy Huguenot adult plant resistance in Australia over the past 90 yr indicates the possibility of durable resistance, When transferred to the hexaploid level the gene should provide a valuable supplement to Sr2.