Influence of A1 cytoplasmic substitution on the downy-mildew incidence of pearl millet.

Large-scale cultivation of pearl millet [Pennisetum glaucum (L.) R. Br. F1 hybrids in India has led to increased incidence of downy-mildew (Sclerospora graminicola). There is concern that the A1 male-sterile cytoplasm used in all the hybrids released so far is responsible for this increase. The influence of A1 malesterile cytoplasm on downy-mildew incidence in pearl millet was studied by comparing the disease reaction of 40 pairs of F1 hybrids, each pair carrying respectively a1 male-sterile and normal B cytoplasm. Mean downy-mildew incidence was similar in the hybrids carrying either A1 male-sterile or B cytoplasm. The general combining ability of lines with and without A1 cytoplasm was found to be similar for downy-mildew incidence. These results indicated that in pearl millet A1 cytoplasm is not associated with increased downymildew incidence. The possible danger of using only one source of cytoplasm has been briefly discussed.