REPRODUCTION, CYTOLOGY, AND FERTILITY OF PEARL-MILLET X PENNISETUM-SQUAMULATUM BC4 PLANTS

Asexual reproduction by means of apomixis that allows production of true-breeding hybrids has tremendous potential for improving world food and feed production. Genes that control obligate apomixis are usually found in the noncultivated wild species. In the study reported here, progenies were established from seven apomictic backcross (BC)-4 plants in a program designed to transfer genes controlling apomixis from Pennisetum squamulatum Frens (2n=6x = 54) to cultivated pearl millet [P. glaucum (L.) R. Br. (2n = 4x = 28)]. The most highly apomictic plants had 2n = 27 or 29 chromosomes. A highly apomictic derivative from a 29-chromosome plant had 28 chromosomes plus a telocentric fragment. BC4 plants and their apomictic progeny more closely resembled cultivated pearl millet in morphology than did an apomictic BC3 plant. On the average, chromosomes of the BC4 plants had one more bivalent and two less univalents than those of the BC3 plants, indicating that the alien chromosomes are being lost. Seed set for BC4 plants ranged from 3% to 16% compared to about 5% for BC3 plants. High rates of ovule abortion were observed after day 11 or 12 in both BC3 and BC4 plants. No BC4 plants were obligately apomictic, but one (A22) produced 89% maternal progenies. Six of the seven BC4 plants produced some progeny that formed only aposporous embryo sacs. This study indicates that it should be possible to produce apomictic pearl millet. © 1993 The American Genetic Association.