29. Analysis of seed and maternal genetic effects on milling quality characters in Indica hybrid rice

Chun-Hai SHI and Jun ZHU

Agronomy Department, Zhejiang Agric. University, Hangzhou, 310029 China

A new generation starts from the fertilization of female and male gametes in both embryo and endosperm, while the parental plant provides the seed coat and nutrients for the new-generation seeds. Therefore, the milling-quality characters in F2 are influenced by genes of F1 plants and F2 seeds. Zhu (1992) has developed a model for quantitative characters of seeds of cereal crops. In this model, it is assumed that the total genetic effect on a seed can be partitioned into seed genetic effect (Go) and maternal effect (Gm). Go is partitioned further into additive (A) and dominance (D) components. Gm is also partitioned into maternal additive (Am) and maternal dominance (Dm) components. Using this model, we have studied the seed and maternal genetic effects on milling-quality characters in Indica hybrids.

MINQUE (0/1) method (Zhu 1992), which is a Minque method with all prior variances setting 1 and all prior covariances setting 0, was used to estimate variance components of seed genetic effects (δ2A and δ2D) and maternal genetic effects (δ2Am and δ2Dm). The components of genetic covariance between seed genes and maternal genes (δ2A.Am and δ2D.Dm) were also estimated. The random predicted by the Adjusted Unbiased Prediction (Aup, Zhu genetic effects were 1993) approach with Minque (0/1) method. The Jackknife method was applied for obtaining estimators or predictors and their standard errors, and for the t-test parameters (Miller 1974).

Incomplete diallel crosses were made using six male-sterile lines (Zhenshan 97A, Erjiuqing A, Erijiunan 1A, V20A, Zhenan 1A, and Zhenan 3A) as females and three restorer lines (Cezao 2-2, T49 and 26715) as males. F2 seedlings of 18 crosses and their parents were transplanted into the field each in three rows of 12 plants at 20 x 20 cm spacing, with two replications in 1991. Seeds from 10 plants of the middle row were used to measure the milling-quality characters, including brown rice weight (mg), milled rice weight (mg), brown rice recovery (%), milled rice recovery (%), and head rice recovery (% head rice to total milled rice).

The results showed that milling-quality characters were controlled by both seed genotype and maternal genotype. As shown in Table 1, brown rice weight and milled rice recovery were mainly controlled by materinal effects. Head rice recovery was controlled by seed dominance effect, while brown rice weight was also conditioned by seed additive effect, but not by seed dominance effect. Seed dominance effect was not found also for brown rice recovery and milled rice recovery.

Predicted genetic effects showed that V20A and Erjiunan 1A were superior in brown rice weight, and Erjiuquing A was better in milled rice recovery than other parents. Crosses Zenshan 97A x T49, Zhenshan 97A x Cezao 2-2 and Zhenan 1A x T49 showed an increase in milled rice recovery, and crosses Zhenan 1A x T49 and Zenan 3A x Cezao 2-2 showed an increase in head rice recovery.

References

Miller, R.G., 1974. The Jackknife, a review. Biometrika 61: 1-15.

Murai, M. and T. Kinoshita, 1986. Diallel analysis of traits concerning yield in rice. Japan. J. Breed. 36: 7-15.

Rao, C.R., 1971. Estimation of variance and covariance components in Minque theory. J. Multivar. Analy. 1: 257-175.

Zhu, J., 1992. Mixed model approaches for estimating genetic variances and covariances. J. Biomath. 7(1): 1-11.

Zhu, J., 1993. Methods of predicting genotype value and heterosis for offspring of hybrids. J. Biomath. 8(1): 32-44.