Assays for the transcript levels of ESTs Ps28, Ps85, Ps159, Ps259, and Ps261 in P. striiformis f. sp. tritici. RNA samples were isolated from urediniospores, germinated urediniospores, or leaves of wheat cultivar Huixianhong inoculated with CY32 and collected at the indicated time points. The expression level of these genes was calculated by the comparative Ct method with the actin gene of P. striiformis f. sp. tritici as the endogenous reference for normalization. Relative quantification was computed with their expression levels in different stages in comparison to that in urediniospores. The average and standard error were calculated from three biological replicates. S, urediniospores; GS, germinated urediniospores; dpi, days post inoculation.