Characteristics and Stability of a New Cytoplasmic‐Nuclear Male‐Sterile Source in Pearl Millet

Stable cytoplasmic‐nuclear male sterile lines are desirable for producing commercial hybrids. The A 1 cytoplasm in pearl millet, Pennisetum glaucum (L.) R. Br., is widely used but produces fertile revertants. The objectives of this study were to evaluate the stability of male sterility in a cytoplasm (A m ) transferred from P. glaucum (L.) R. Br. subspecies monodii (Maire) Brunken and to determine if this cytoplasm differed from the A 1 , A 2 , and A 3 cytoplasms. In 1983, seeds of male‐sterile ‘Tift 23A 1 ’ and ‘Tift 23a m ’ were stored at 24, 5, and −5 °C. In 1984 to 1986, seeds of each line were planted in the field and observed daily at anthesis for fertile revertants. Male sterility of the line with A m cytoplasm is maintained by the maintainer lines of A 1 , A 2 , and A 3 cytoplasms. Seven tester lines restored full or partial male fertility to hybrids with A 1 , A 2 , and A 3 cytoplasms but only two of the testers restored male fertility to hybrids with A m cytoplasm. Plants with A 1 cytoplasm are 2 or 3 d earlier than plants with A 1 cytoplasm and have darker red anthers than those with A 1 cytoplasm. In 3 yr, male‐sterile plants with A 1 cytoplasm averaged 0.91 fertile revertant events per 1000 inflorescences, while no fertile revertants were observed for plants with A m cytoplasm. The number of fertile revertants for A 1 cytoplasm increased with age of seed from 1 to 3 yr. Seeds stored at 24 °C produced plants with significantly more fertile revertants than seeds stored at 5 or −5 °C. Differences in seed germination and vigor of seedlings with A 1 and A m cytoplasms were nonsignificant or of little practical significance. The new cytoplasm, desiganted A 4 , is different from A 1 , A 2 , and A 3 cytoplasms based on fertility of hybrids, morphological characters, and stability.