Measuring the cost of resistance to Puccinia coronata CDA in Avena fatua.
In greenhouse and field plot experiments, 15 oat lines selected from a natural population in Canberra were compared. Genotypes susceptible to P. coronata showed no difference in the rate of germination at 15, 20 or 25°C. Resistant lines were similar to susceptible lines at 15° but were progressively slower to germinate at 20 and 25°. The relative fecundity of resistant and susceptible genotypes, growing in mixtures in a disease-free environment, varied with temp. At high temp. in the greenhouse, susceptible genotypes performed consistently better than resistant genotypes. At low temp. the reverse was true. No conclusions about the cost of resistance could be made because of the apparently chance correlations between resistance and late germination in oats. It was not possible to separate the effects, if any, of specific resistance alleles from the correlated structure of the entire genome of this highly inbreeding species.