Fig. 1. Frequency distributions of spikelet length and spikelet width in F`2` population of AT-13OxKitaake.
Plant Breeding, Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
Various kinds of mutants have been induced by gamma irradiation of anther culture of Kitaake (Kinoshita et al. 1989; Takamure and Kinoshita 1993). A small grain mutant (AT-130) was found in the progeny of a doubled haploid after a chronic irradiation of anther calli with an exposure dose of 194Gy. AT-130 had small grains, late heading and low seed fertility and bred true.
The F`1` and F`3` populations from AT-13OxKitaake indicated that a single recessive gene designated as mi-k was responsible for the small grain (Fig. 1). Comparison of grain size among different genotypes showed that the gene action to decrease spikelet length and width was prominent (Table 1). The allelism test
Fig. 1. Frequency distributions of spikelet length and spikelet width in
F`2` population of AT-13OxKitaake.
Table 1. Mean spikelet length and width in the three F2 genotypes of
AT-13OxKitaake
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Spikelet
Genotype No. of F`3` lines Length (mm) Width (mm)
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+ + 26 5.74 (100)% 3.75 (100)%
+ mi-k 40 5.66 (99) 3.73 (99)
mi-k mi-k 15 5.14 (90) 3.04 (81)
Total 81
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Goodness of fit; Chi2 (1:2:1)=3.00, d.f.=2, 0.20<p<0.30.
Table 2. Comparison of eight characters between Kitaake and AT-130 grown
under four kinds of conditions
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Character1)
Cultivation _______________________________________________________
CL PL PN NS SF SL sw HP
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Paddy field Kitaake 50.8 14.8 19.8 91.8 46.2 5.98 3.58 95.9
AT-130 44.6* 12.0* 13.0** 77.7* 0 - - 124.2*
(88%) (81) (66) (85) (-) (-) (-) (126)
Plastic house Kitaake 49.5 12.4 11.3 43.9 85.7 5.82 3.53 74.1
AT-130 46.8 11.9 16.6 45.5 28.5 4.70 2.93** 109.5
(95%) (96) (147) (104) (33) (81) (83) (148)
Growth chamber Kitaake 50.3 12.6 11.0 45.2 88.5 5.82 3.41 82.2
20 deg C AT-130 44.3* 9.6* 16.0** 46.2 7.3** 4.50** 2.84 120.2
(88%) (76) (145) (102) (8) (77) (83) (146)
Growth chamber Kitaake 63.9 13.8 8.7 57.3 96.0 5.86 3.54 69.8
28 deg C AT-130 52.2* 10.4** 9.2 56.7 74.4 4.62 2.71 84.8*
(82%) (75) (106) (99) (78) (79) (77) (121)
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1) CL: Culm length (cm), PL: Panicle length (cm), PN: Panicle number, NS:
Number of spikelets per panicle, SF: Seed fertility (%), SL: Spikelet length
(mm), SW: Spikelet width (mm), HP: Heading period (days).
*,**: Difference from Kitaake significant at 5% and 1% levels, respectively.
between AT-130 and H-343 (Mi) indicated that the mi-k locus was different
from Mi located on chromosome 3.Character expression was examined in both AT-130 and the original line, Kitaake under the conditions of paddy field, plastic house and growth chamber kept at 20 deg C and 28 deg C in 1993 (Table 2). In paddy field, Kitaake showed semi-sterility due to low temperatures, while AT-130 showed complete sterility. Since the seed fertility of AT-130 was nearly normal at 28 deg C, its sterility was due to low temperature conditions, and its late heading increased sterility in the paddy field.
References
Kinoshita, T., K. Mori and I. Takamure, 1989. Mutagenesis by means of anther culture combined with gamma irradiation. RGN 6: 139-141.
Takamure, I. and T. Kinoshita, 1993. Inheritance of six kinds of mutants induced by gamma-ray irradiations to anther culture of rice. Mem. Fac. Agr. Hokkaido Univ. 18: 437-446. (in Japanese with English summary)