INFLUENCE OF RACE AND POST INFECTION TEMPERATURE ON 2 COMPONENTS OF PARTIAL RESISTANCE TO WHEAT LEAF RUST IN SEEDLINGS OF WHEAT

Components of partial resistance, infection frequency and latency period, were determined in 71 winter and spring wheat genotypes in the seedling stage, after infection with three races of leaf rust ('Felix 3B', 'Clement B' and 'Betuwe 85C') at three different day/night temperature regimes (24/18-degrees-C, 18/12-degrees-C and 12/6-degrees-C). The genotypes were split into two groups and two separate experiments were carried out. Five genotypes, SVP 84039, Akabozu, Banco, BH 1146 and Orso, conferred a low infection frequency and a long latency period and Westphal 12A a long latency period, indicating a relatively high level of partial resistance. The correlation coefficient between infection frequency and latency period was low. Race-specificity was not found. There was a significant temperature effect on the latency period. In the second experiment the temperature x genotype interaction was significant. Temperature-response functions of transformed data demonstrated that the latency periods of four relatively resistant genotypes, Westphal 12A, Banco, BH 1146 and Orso and of Sarno and Mirela were most sensitive to temperature. The range between the genotypes with the longest and the shortest latency period was highest at 12-degrees-C. Therefore, low temperature regimes are preferred to distinguish differences in level of partial resistance.