C-banding pattern and powdery mildew resistance of Triticum ovatum and four T. aestivum-T. ovatum chromosome addition lines.

C-banding patterns of T. ovatum (Ae. ovata) and four T. aestivum cv 'Poros'-T. ovatum chromosome addition lines are presented, and the added chromosomes of T. ovatum have been identified. Furthermore, nucleolar activity and powdery mildew resistance were analyzed in the 'Poros'-ovatum addition lines and compared to that of T. ovatum and T. aestivum cv 'Poros'. The addition lines II, III and IV and 'Poros' were highly susceptible to powdery mildew isolates nos. 8 and 9, whereas the addition lines VI1 and VI2 showed high resistance. Even for an Ml-k virulent isolate, these two lines were highly resistant. By combining the cytological results and those of the powdery mildew analysis, the added chromosomes of T. ovatum can be excluded from responsibility for the high powdery mildew resistance of the addition lines VI1 and VI2. The same is true for a modified chromosome 6B, which is present in the 'Poros'-ovataum addition lines II, III and VI. The high variation in C-banding pattern observed in the A-, B- and D-genome complement of the addition lines is believed to be the result of crossing different lines of T. aestivum instead of 'Poros' alone. Thus, we cannot trace the powdery mildew resistance back to a specific chromosome.