Department of Soil and Crop Sciences, Texas A & M University College Station, Texas
U.S. Department of Agriculture, Agricultural Research Service
1Present address: Regional Research Station, IARI, Hyderabad (A.P.).
Embryological comparisons of ‘R 473’, an apomictic line of sorghum, Sorghum bicolor (L.) Moench, and a sexual line were made using ovule squashes. Development of megaspores, megagametophytes, embryos, and endosperms was normal in the sexual line and quite different in ‘R 473’. Apomictic embryo sacs were formed from nucellar cells and apparently sometimes from the mega-spore mother cell. Development in ‘R 473’ was irregular and variable. In ‘R 473’, male nuclei were never observed to fuse with the egg. Endosperm formed after fusion of a polar nucleus and a sperm nucleus, and additional embryo sacs were frequently formed. ‘R 473’ was crossed with its F1’s, F2’s, and BG1’s from crosses with a number of other lines. Progenies contained maternals and hybrids, indicating that ‘R 473’ functioned as a facultative apomict in these crosses.
