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 thre e 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 adu lt-plant resistance in Houser and Redcoat was determined by both quali tative and quantitative methods. Mildew severity was used for qualitat ive estimates, and area under the disease progress curve values were u sed for quantitative estimates. Adult-plant resistance to powdery mild ew in Redcoat and Houser is controlled by two to three genes. Disease reactions of the parents and progenies of resistant X susceptible cros ses indicated that resistance in both cultivars is partially dominant and additive. Broad-sense heritability, estimated by the variance comp onents 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 a dult-plant resistance among progeny derived from crosses with Redcoat and Houser would likely be most effective in advanced generations.