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 F\2\ are influenced by genes of F\1\ plants
and F\2\ 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
(G\o\) and maternal effect (G\m\). G\o\ is partitioned further into
additive (A) and dominance (D) components. G\m\ is also partitioned into
maternal additive (A\m\) and maternal dominance (D\m\) 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 (delta2\A\ and delta2\D\) and maternal genetic effects (delta2\Am\ and delta2\Dm\). The components of genetic covariance between seed genes and maternal genes (delta2\A.Am\ and delta2\D.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, V\20\A, Zhenan 1A, and Zhenan 3A) as females and three restorer lines (Cezao 2-2, T49 and 26715) as males. F\2\ 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.
Table 1. Genetic variances and covariances of milling-quality characters
in Indica rice hybrids
========================================================================= Variances & Characters covariances ======================================================== BRW MRW BRR MRR HRR ========================================================================= delta2A 0.204* 0.078 0.003 0.115 0 delta2D 0.034 0 0 0 32.5** delta2Am 0.091* 0.035 0.002 0.052 0 delta2Dm 0.778 0.155 0.582 1.602** 0 delta2A.Am 0.015 0.026 -0.109 0.094 9.5 delta2D.Dm 0.271 0.104 0.004 0.154 -10.2 delta2e 0.478* 0.781* 4.377 1.548 44.4** ========================================================================= BRW: Brown rice weight (mg) MRW: Milled rice weight (mg) BRR: Brown rice recovery (%) MRR: Milled rice recovery (%) HRR: Head rice recovery (%) *, ** Significant at 5% and 1% levels, respectively. As to estimation methods, see Rao 1971.
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.