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 A1 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 (Am) transferred from P. glaucum (L.) R. Br. subspecies monodii (Maire) Brunken and to determine if this cytoplasm differed from the A1, A2, and A3 cytoplasms. In 1983, seeds of male-sterile ‘Tift 23A1’ and ‘Tift 23am’ 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 Am cytoplasm is maintained by the maintainer lines of A1, A2, and A3 cytoplasms. Seven tester lines restored full or partial male fertility to hybrids with A1, A2, and A3 cytoplasms but only two of the testers restored male fertility to hybrids with Am cytoplasm. Plants with A1 cytoplasm are 2 or 3 d earlier than plants with A1 cytoplasm and have darker red anthers than those with A1 cytoplasm. In 3 yr, male-sterile plants with A1 cytoplasm averaged 0.91 fertile revertant events per 1000 inflorescences, while no fertile revertants were observed for plants with Am cytoplasm. The number of fertile revertants for A1 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 A1 and Am cytoplasms were nonsignificant or of little practical significance. The new cytoplasm, desiganted A4, is different from A1, A2, and A3 cytoplasms based on fertility of hybrids, morphological characters, and stability.
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