Assessment of Urediniospore Germination of Puccinia striiformis at Various Temperatures on Agar and Detached Leaves of Wheat

The percentage of urediniospore germination of two isolates of yellow rust {Puccinia striiformis f. sp. tritici) namely, WYR ۶۹/۱۰ |Race ۱۰۴E ۱۳۷(۱)] and isolate WYR ۷۹/۴ |Race ۴۱E ۱۳۹ (۴)], was studied at various temperatues between ۵-۲۰°C on agar and the adaxial surface of detached leaves on a layer of benzimidazole agar. Four replicates for five temperature treatments were arranged as a preliminary investigation to find the most appropriate temperature for the subsequent comparison of spore germination on the host material under investigation. Mean percentage values were analysed separately and the levels of urediniospore germination at different temperatures were compared using analysis of variance and Student- Newman-Keuls techniques. Spore germination of both isolates was high over the temperature range ۵-۱۰°C, but dropped significantly at ۱۵-۲۰°C . At the cooler temperatures ۵° , ۷.۵° and ۱۰°C , isolate WYR ۶۹/۱۰ consistently germinated at a higher level than isolate WYR ۷۹/۴ , whereas at ۲۰°C, the latter isolate gave the highest figures. This observation indicates that both isolates germinated most effectively at ۱۰°C on agar and detached leaves.