H. YASUI, H. SATOH and N. IWATA
Faculty of Agriculture, Kyushu University, Hakozaki, Fukuoka, 812 Japan
We have attempted to obtain trisomic plants by using a desynaptic mutant, MM 15, which was induced by a treatment of fertilized egg cells with N-methyl- N-nitrosourea (MNU) in the Japonica variety Kinmaze (Kitada and Omura 1983). Strain MM 15 is homozygous for a recessive desynapsis gene and nearly completely self-sterile. It was crossed with Kinmaze, and all F1 seeds obtained were sown on agar medium and the seedlings were transplanted in an experimental field. We examined morphological features of the F1 plants and screened for trisomics.
From crosses made in 1983 and 1986, we obtained 4,145 F1 seeds (Table 1). The crossability was 8 percent in 1983 and 16 percent in 1986. The F1 plants developed in 1982, 1983 and 1987 were classified into disomic (76.1%), trisomic (21.0%), double-trisomic (2.1%) and plants with other chromosomal aberrations including reciprocal translocation (0.8%) (Table 2). Possible twelve types of trisomic plants as judged from morphological features were obtained in the F1 population (Table 3; Iwata et al. 1970). They were each confirmed to have 25 chromosomes by cytological examination.
The trisomic series so far established in a Japonica (Iwata and Omura 1984) and an Indica rice variety (Khush et al. 1984) have been obtained by screening
Table 1. Cross- and self-fertilities of a desynaptic mutant MM15 ________________________________________________________________ Pollination Year No. of spikelets No.of Fertility pollinated seeds set (%) ________________________________________________________________ MM15 X Kinmaze 1983 31,054 2,507 8.1 MM15X Kinmaze 1986 10,558 1,638 15.5 MM15, open 1983 1,351 6 0.5 MM15, bagged 1986 (No record) 0 0 ________________________________________________________________ Table 2.Diploids and aneuploids found among the F1 plants from MM15 X Kinmaze ________________________________________________________________ Year Diploid Trisomics Double- Others Total no. trisomics of plants ________________________________________________________________ 1982 246 63 (20%) 4 0 313 1983 60 17 (22%) 0 0 77 1987 512 146 (21%) 18 9 685 Total 818 226 (21%) 22 9 1,075 ________________________________________________________________ Table 3. Number and frequency (%) of each type of trisomics obtained in the F1 plants from MM15 X Kinmaze ________________________________________________________________ Typea Character nameb 1982 1983 1987 Total No. % No. % No. % No. % ________________________________________________________________ A Pale 5 7.9 2 11.8 12 8.2 19 8.4 B Awned 4 6.3 1 5.9 6 4.1 11 4.9 C Small grain 9 14.3 1 5.9 18 12.3 28 12.4 D Erectoides 8 12.7 1 5.9 12 8.2 21 9.3 E Spreading 7 11.1 0 21 14.4 28 12.4 F Rolled leaf 7 11.1 4 23.4 4 2.7 15 6.6 G Pseudo-normal 2 3.2 0 16 11.0 18 7.9 H Large grain 9 14.3 2 11.8 20 13.7 31 13.7 L Short panicle 9 14.3 3 17.6 13 8.9 25 11.1 M Sterile 1 1.6 0 3 2.1 4 1.8 N Smooth glume 0 2 11.8 5 3.4 7 3.1 0 Grassy 2 3.2 1 5.9 16 11.0 19 8.4 Total 63 (100) 17 (100) 146(100) 226(100) ________________________________________________________________ a. Corresponding to the type code given by Iwata et al.(1970). b. Corresponding to the name given by lwata and Omura (1984).the progeny of crosses between autotriploid and diploid plants. In the present study, a new trisomic series was raised from the progeny of a desynaptic mutant. Such a desynaptic mutant is easily obtained by the MNU treatment of panicles (Kitada et al. 1983). These mutants are a useful source of trisomic plants. The desynapsis gene can be transferred to other varieties by hybridization.
References
Iwata, N., T. Omura and M. Nakagahara, 1970. Studies on the trisomics in rice plants (Oryza sativa L.), 1. Morphological classification of trisomics. Jpn. J. Breed. 20: 230-236.
Iwata, N. and T. Omura, 1984. Studies on the trisomics in rice plants (Oryza sativa L.), VI. An accomplishment of a trisomic series in japonica rice plants. Jpn. J. Genet. 59: 199-204.
Khush, G. S., R. J. Singh, S. C. Sur and A. L. Librojo, 1984. Primary trisomics of rice: Origin, morphology, cytology and use in linkage mapping. Genetics 107: 141-163.
Kitada, K., N. Kurata, H. Satoh and T. Omura, 1983. Genetic control of meiosis in rice, Oryza sativa L., I. Classification of meiotic mutants induced by MNU and their cytological characteristics. Jpn. J. Genet. 58: 231-240.
Kitada, K. and T. Omura, 1983. Genetic control of meiosis in rice, Oryza sativa L., II. Cytological analyses of desynaptic mutants. Jpn. J. Genet. 58: 567-577.