In order to obtain new mutants for linkage mapping
in rice, seeds of IR68 were presoaked for 16 hours and treated with 1.0%
EMS solution (prepared in phosphate buffer pH 7.0) for 10.5 hrs at 30°C
over a temperature controlled shaker. A spotted leaf mutant was isolated
from M2 population. True breeding nature of the mutant was confirmed
in M2. The mutant shows rust colored spots which start appearing
at maximum tillering stage and continue until maturity. The spots are distributed
throughout the leaf blade with maximum concentraion along the midrib (Fig.
1 ). Inheritance of this mutant was studied by crossing it with IR68. The
F1 was normal and in an F2 population of 118 plants,
92 were normal and 26 were mutant. These data agree with a 3 normal : 1
mutant ratio. Thus the mutant phenotype is due to a single recessive gene.
The F1s of this mutant with spl-1,
spl-2, spl-3, spl-4, spl-5, spl-6, spl-7 and spl-9 were all
normal. As the data of Table 1 show, the F2 populations except
that from its cross with spl-5 segregated in a ratio of 9 normal
: 7 mutant thereby showing that the mutant is non-allelic to and independent
of spl-1, spl-2, spl-3, spl-4, spl-6, spl-7 and spl-9. The
F2 population of its cross with spl-5 did not fit to
9:7 ratio (c2 =16.6) thereby
indicating linkage of this mutant with spl-5 which is located on
chromosome 7. Allele tests of the mutant with spl-8 and spl-10
could not be carried out due to non-availability of seeds of these mutants.
However, spl-8 is located on chromosome 5 (lwata et al. 1978)
and spl-10 is located on chromosome 10 (Ideta et al. 1993).
Thus, the new mutant is also different from spl-8 and spl-10
and is designated as spl-ll.
Table 1. Segregation of spl-ll with other spl mutants.
Cross | Total | Normal | spl | c2 (9:7) |
spl-ll/spl-I | 114 | 64 | 50 | 0.0005 |
spl-ll/spi-2 | III | 70 | 41 | 2.093 |
spl-ll/spl-3 | 120 | 77 | 43 | 3.056 |
spl-4/spl-ll | 74 | 48 | 26 | 2.231 |
spl-ll/spl-5 | 119 | 89 | 30 | 16.620** |
spl-6/spl-ll | 111 | 69 | 42 | 111 |
spl-ll/spl-7 | 120 | 72 | 48 | 0.690 |
spl-ll/spl-9 | 130 | 84 | 46 | 3.696 |
References
Ideta, O., A. Yoshimura, T. Matsumoto, H. Tsunematsu, H. Sato and N.
Iwata, 1993. Integration of conventional
and RFLP linkage maps in
rice, II. Chromosomes 6, 9, 10 and 11. RGN 10: 87-89.
Iwata, N., T. Omura and H. Satoh, 1978. Linkage studies in rice (Oryza
sativa L.) on some mutants for
physiological leaf spots.
J. Fac. Agr. Kyushu Univ. 22: 243-251.