Fig. 1. Relationship between length and length/width of seeds of primary trisomics and disomics. X, Disomics. A~H, Primary trisomics, letters correspond to respective trisomic types.
Tropical Agriculture Research Center, 1-2 Ohwashi, Tsukuba, 305 Japan
The primary trisomics of O. sativa showed characteristic features in panicle and spikelet characters. They could not be distinguished from one another and from the disomics clearly before the heading of the plants. Iwata et al. (1970) reported that the 12 types could be characterized clearly by the length, width and length/width ratio of spikelets and culm length. Spikelet characters are useful for classification particularly because they can be used even though the number of plants available is small.
In O. glaberrima Steud., 8 types of primary trisomics were distinghished by
Fig. 1. Relationship between length and length/width of seeds of primary
trisomics and disomics. X, Disomics. A~H, Primary trisomics, letters
correspond to respective trisomic types.
morphological and reproductive features (Ishiki 1987, 1991). Seed characters like length and length/width ratio of spikelets were relatively uniform within the types and varied distinctly among the types. The relationships between the length and leiigth/width ratio of spikelets were surveyed in the primary trisomics and disomics. Their distributions are shown in Fig. 1. The trisomic and disomic plants also differed in awn length and percent sterility. For example, trisomic types A and F overlapped in seed characters, but they could be distinguished since A had long awns and F was awnless. Types D and G also overlapped, but D was sterile because of degeneration of stigmas and had short awns, and G showed some fertility and was awnless. In this way, the primary trisomic and disomic plants were distinguished from one another by seed characters and some other features although the number of plants was small.
References
Iwata, N., T. Omura and M. Nakagahra, 1970. Studies on the trisomics in rice plants (Oryza sativa L.), I. Morphological classification of trisomics. Jpn. J. Breed. 20: 230-236.
Ishiki, K., 1987. Breeding of primary trisomics in African rice, Oryza glaberrima Steud. Ph. D. Dissertation, Osaka Prefecture Univ. 176pp.
Ishiki, K., 1991. Cytogenetical studies on African rice, Oryza glaberrima Steud. 3. Primary trisomics produced by pollinating autotriploid with diploid. Euphytica 55: 7-13.