Investigations to identify quantitative trait loci (QTLs) governing cooking quality traits including amylose content, gel consistency and elatinization temperature (expressed by the alkali spread value) were conducted using a set of 241 RIL populations derived from an elite hybrid cross of "Zhenshan 97" 9 "Minghui 63" and their reciprocal backcrosses BC1F1 and BC2F1 populations in two environments. QTLs and QTL 9 environment interactions were analyzed by using the genetic model with endosperm and maternal effects and environmental interaction effects on quantitative traits of seed in cereal crops. The results suggested that a total of seven QTLs were associated with cooking quality of rice, which were subsequently mapped to chromosomes 1, 4 and 6. Six of these QTLs were also found to have environmental interaction effects.

Identification of genetic main effects and genotype

on heterosis and cytoplasm interaction heterosis were more important for protein content，but endosperm heterosis was only important for lysine content in GE interaction heterosis. It was shown that some indiea hybrid crosses had significant positive heterosis for protein content. Negative heterosis for lysine content was observed in most hybrid crosses.

It is necessary for rice breeders to understand the genetic basis of nutrient quality traits of rice. Essential amino acids are most important in determining the nutrient quality of rice grain and can affect the health of people who depend on rice as a staple food. In view of the paucity of genetic information available on essential amino acids in indica rice, we estimated the genetic main effects and genotype×environment (G×E) interaction effects on the content of essential amino acids. Nine cytoplasmic male sterile lines as females and five restorer lines as males were introduced in a North Carolina Ⅱ design across environments. Estimates of the content of the essential amino acids valine, methionine, leucine and phenylalanine showed that they were mainly controlled by genetic main effects, while the contents of threonine, cysteine and isoleucine were mainly affected by G×E effects. In the case of genetic main effects, both cytoplasmic and maternal genetic effects were predominant for all essential amino acids, indicating that selection for improving essential amino acid content based on maternal performance would be more effective than that based on seeds. The total narrow-sense heritabilities were high and ranged from 0.72 to 0.83. Since general heritabilities for these essential amino acids (except for cysteine) were found to be much larger than G×E interaction heritability, the improvement of content of most essential amino acids under selection would be expected under various environments.

The low fertility of naked seed rice (NSR) was investigated by the following observations: somatic chromosome constitute, behavior of pollen mother cells (PMCs), the germination of mature pollen grains, the development of male and female gametes and the structure of the anther opening. The results indicated that somatic chromosomal number was 2n=24, behavior of PMCs were normal and most of pollen grains could regularly develop further to mature male gametophytes in NSR. And dehiscence chamber and thickened endothecium cell (TEC) in numerous anthers of the NSR were developed abnormally after dicaryotic phase, result in few anthers complete opening and most partly opening or failure to opening, therefore much fewer of pollen grains attach on the stigma as compared with normal variety. Furthermore most of embryo sacs possessed abnormal structure and were sterile. All of above illustrated that the failure of the anther opening and the abortion of female gametophyte were main factors controlling the low seed-setting rate of the NSR.