Investigations on resistance to disease among species of the genus Avena: II. Resistance to physiologic races of Puccinia coronata avenae and P. graminis avenae
Williams, W.; Verma, U.N.
Ann Appl Biol 44(3): 453-460
A collection of 53 samples representing diploid and tetraploid species of Avena were tested for resistance to 3 races of crown rust and 2 of stem rust. Resistance to some races of the 2 rust species was confined to 1 sample of subsp. strigosa and 2 samples of subsp. barbata of A. strigosa. Sample 20, representing subsp. barbata, alone possessed resistance to all the races of both rust species. This material had previously been shown to be resistant to 6 races of smuts (Ustilago spp.). Genotypes possessing combinations of resistance to a wide range of pathogens appear to be very rare, and intra-specific variation in respect of these characters is so great that taxonomic classification cannot be used with any degree of certainty to discover sources of resistance to disease. The discovery of widespread resistance in a sample of the tetraploid subsp. barbata offers possibilities of the direct transference of genes to the cultivated species, thus dispensing with the need to synthesize amphidiploid bridging forms. The reaction of the hexa-ploid variety, Richland, to stem rust proved to be sensitive to temperature. Resistance mechanisms that are subject to environmental influences are considered to be less effective in combating the evolution of new races of the pathogen.