31. Genetics of stigma exsertion in rice

Tao Li and Yi-Wu Chen

Rice Institute, Hunan Academy of Agricultural Sciences, Mapoling, Changsha, Hunan, China

Stigma exsertion is an important character for improving the production of hybrid seed. From studies of hybrid populations, we have recognized the following in relation to this character:

1. The inheritance of stigma exsertion is quantitative, as this trait shows a continous variation in hybrid populations.

2. No cytoplasmic effect was recognized on stigma exsertion, although the male sterility of "WA" type had a positive effect on the rate of stigma exsertion.

3. Among genic effects, the dominance effect was the largest, followed by the additive effect. Epistasis effect was slight.

4. Among floral characteristics, stigma exsertion showed a high heritability, followed in descending order by stigma length, spikelet width, stigma width, spikelet length, stigma angle, and ovary length.

5. Stigma exsertion was positively correlated with stigma length, spikelet length, stigma angle and ovary length, and was negatively correlated with spikelet width.

6. The direct effects of floral characteristics on stigma exswertion were in descending order: stigma angle, ovary length, stigma length and spikelet length.

7. Significant correlations were found between the F1 and parental or mid- parental values, and also between F2 and F3 plants.

8. The estimates of genetic advance of stigma length and spikelet length were greater than those of other floral characteristics.

These experimental results indicate that improvement of stigma exsertion by selection is possible and selection may be made in early generation hybrids.