Experimental Farm, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
The F\1\ plants of crosses between distantly related rice varieties, as
well as the wild relatives of cultivated rice, often show black hull
coloration. It was reported that the black hull coloration was controlled by
one dominant gene (Kuang et al. 1946; Jodon 1964), or two complementary genes
(Chao 1928; Mitra and Gangull 1937; Kuriyama and Kudo 1967), or three
complementary genes (Nagao and Takahashi 1954; Rao and Seetharaman 1973).
The present author confirmed that the complementary genes controlling this
character were three, symbolized as Bh-a, Bh-b and Bh-c. The Ph gene for
phenol reaction was also found to be responsible for this character (Kuriyama
and Kudo 1967; Rao and Seetharaman 1973), and to correspond to Bh-c. The
frequency of Ph is high in the Indica and low in the Japonica type (Oka
1953); phenol reaction can be used for distinguishing between the two types
with an about 10% probability of mis-classification (Morishima and Oka 1981).
Kinoshita and Takahashi (1976) suggested that the distributions of Bh-a and
Bh-b were also localized geographically in relation to the Indicajaponica
differentiation.
The presence of dominant or recessive allele at the Bh-a and Bh-b loci in a given variety can be known by observing the F, plants from crosses with test strains having Bh-a + Bh-c (=Ph) and + Bh-b Bh-c (=Ph), respectively, and that for the Bh-c locus simply by phenol reaction of the grain. By this method, a total of 294 varieties from different parts of the world were examined. The result showed that among the varieties sampled, the frequency of Bh-a was high (79.6%) while that of Bh-b was much lower (15.6%); the frequency of Bh-c (=Ph, representing the Indica type) was 25.5%. Ph and Bh-b were recombined at random, but the association between Ph and Bh-a, as well as between Bh-a and Bh-b, significantly deviated from random assortment. Most varieties with Ph had Bh-a, while about 1/3 of varieties with ph (Japonica) had its recessive allele (bh-a, shown by + in Table 1).
The geographical distribution of these genes is shown in Table 1. The frequency of Bh-a was highest (100%) in the varietal groups from India, Sri Lanka, Pakistan, Burma, Nepal and Bhutan, and was lowest (27%) in the varieties from Hokkaido, Japan. In contrast, the frequency of Bh-b, which was generally low in other regions, was quite high (78%) among Hokkaido varieties.
Table 1. Geographical distribution of genotypes for three genes controlling
black hull coloration (in %)
=============================================================================
Bh-c (=Ph) +(=ph)
Bh-a Bh-a + + Bh-a Bh-a + + No.of
Region var. s
Bh-b + Bh-b + Bh-b + Bh-b + tested
=============================================================================
Japan, Hokkaido 4.6 13.6 9.1 59.1 13.6 22
Japan, other parts 1.4 1.4 59.5 2.7 35.1 74
China, Korea & Taiwan 62.8 7.0 25.6 2.3 2.3 43
Indochina & Philippines 7.1 85.7 7.1 14
Indonesia 21.7 69.6 8.7 23
India, Sri Lanka,
Pakistan & Burma 12.9 40.3 6.5 40.3 62
Nepal & Bhutan 6.3 31.3 6.3 56.3 16
USSR & East Europe 33.3 55.6 11.1 9
U.S.A. 4.0 8.0 52.0 36.0 25
Others 16.7 83.3 6
=============================================================================
Total 3.4 21.8 0.3 6.1 48.3 5.8 14.3 294
Expected from X2=
random combination 3.2 17.1 0.8 4.4 9.3 50.0 2.4 12.8 35.6a
=============================================================================
a - Comparison between observed and expected numbers of varieties,
significant at 1% level.
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Jodon, N. E., 1964. Genetic segregation and linkage, important phases of rice research. In Rice Genetics and Cytogenetics (ed. IRRI), p.193-204. Elsevier, Amsterdam.
Kinoshita, T. and M. Takahashi, 1976. Comparative genic analysis on the black hull coloration in rice. Jpn. J. Breed, 26, Suppl. 1: 106-107. (in Japanese)
Kuang, H. H., D. S. Tu and Y. H. Chang, 1946. Linkage studies of awn in cultivated rice (Oryza sativa L.). J. Genetics 47: 249-256.
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Mitra, S.K.I.A.S. and P. M. ganguli, 1937. Inheritance of inner glume colour in rice. Ind. J. Agr. Sci. 7: 126-133.
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Rao, C. H. and R. Seetharaman, 1973. Genetic studies in pericarp and hull color in rice. Ind. J. Genet. Pl. Breed. 33: 319-323.