Journal of Taiwan Agricultural Research

Author:Charng-Pei Li, Yih-Chuan Kuo and Shu-Tu Wu

Abstract:

    Two sinica cultigens, Tainung 67(TNG 67) and Taiken 1(TK 1), and a wild rice, O. nivara (Acc.104705) were used as the recurrent parents and donor parent, respectively, to investigate the genetic behaviors for the seed coat (brain) color, grain length, grain width, and grain shape (length-width ratio) of the interspecific hybrid progenies of Oryza species. The F₁, F₂, BC₁F₁, BC₁F₂, BC₂F₁, BC₂F₂, BC₃F₁ and BC₃F₂ populations of two cross combinations were simultaneously planted at the experimental farm of Taiwan Agricultural Research Institute in the first crop of 1996. In normal growth conditions, the seed coat color of O. nivara is brown, and the shape of grain is slender, on the other hand, two sinica cultigens are light brown in seed coat color and bold in grain shape. It is indicated from our data that the seed coat color is conditioned by one major gene, and brown seed coat is dominant. Furthermore, linkage was not found between seed coat color and grain length, width and shape of brown rice. Heterosis was found in grain length in both cross combinations. Few are transgressive in both F₂ populations, and the frequency distributions of grain length in various backcross populations are peaked and leaned toward the recurrent parents, cultigens. For grain width, heterosis was only found in TK 1 X O. nivara combination. However, transgressive segregation was indicated in both F₂ populations. Variation of grain width in various backcross populations TNG 67 X O. nivara combination appeared to be larger than those in TK 1 X O. nivara. As for grain shape, bold shape was observed in both F₁ populations. Transgressive segregation was observed in both F₂ populations, and frequency distribution was peaked only in various backcross populations of TK 1 X O. nivara cross combination. In general, the mean performance for length, width, and shape of brown rice in F₂ and various backcross populations were lower than those in F₁ populations, indicating that the genes concerned might be additive. The broad sense heritabilities estimated for the three grain traits were relative high in both F₂ and BC₁F₂, and heritabilities appear to lower along with increase in the number of backcross except grain width in BC₃F₂ population in TNG 67 X O. nivara combination. In F₂ populations of both cross combinations, it was found that there is a positive correlation between grain shape and length, and a negative correlation between grain shape and width in various populations. Data were also observed that there is no significant relationship between grain length and width in both F₂ and BC₁F₂ populations, however, a positive correlation was observed in BC₃F₂ populations.

Key words:Oryza sativa, O. nivara, interspecific hybridization, recurrent backcross, brown rice

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