HERITABILITY AND NUMBER OF GENES GOVERNING ADULT-PLANT RESISTANCE TO POWDERY MILDEW IN HOUSER AND REDCOAT WINTER WHEATS

Heritability and number of genes controlling adult-plant resistance to powdery mildew (Blumeria graminis f. sp. tritici) was studied in three winter wheat (Triticum aestivum L.) crosses. Parents, F-1, F-2, F-3, and backcross populations were evaluated in the field under naturally occurring inoculum of powdery mildew. Number of genes controlling adult-plant resistance in Houser and Redcoat was determined by both qualitative and quantitative methods. Mildew severity was used for qualitative estimates, and area under the disease progress curve values were used for quantitative estimates. Adult-plant resistance to powdery mildew in Redcoat and Houser is controlled by two to three genes. Disease reactions of the parents and progenies of resistant X susceptible crosses indicated that resistance in both cultivars is partially dominant and additive. Broad-sense heritability, estimated by the variance components method, ranged from 0.57 to 0.94, while heritability estimated by the standard units method ranged from 0.19 to 0.35. Selection for adult-plant resistance among progeny derived from crosses with Redcoat and Houser would likely be most effective in advanced generations.