利用7射线和EMs溶液诱变处理籼稻“93lJ”种子，经过M：筛选和M,重复鉴定，分别获得465份和210份（共675份）叶、茎、穗和根等性状变异的突变体，突变频率为5．62％。7射线诱变群体的变异范围要大于EMs诱变群体，突变频率也较高，但紫色叶鞘和叶片类病斑等少数突变类型只在EMS诱变群体中出现。新构建的突变体库将有助于进一步开展水稻功能基因的研究。

Following the sequencing of rice genome, the functional analysis of unidentified genes is gaining wide importance. For these, mutant isolation is one of the effective ways to isolate and clone the target genes and analyze their functions. For finding the various mutants in the same genetic background, seeds of Oryza sativa cv. Nipponbare were treated with ethyl methane sulphonate (EMS). A total of 1056 mutants for five categories were screened in M2 generation with the seedling frequency of 26.29‰ at three-leaf stage, but only 264 mutants were verified in M3 generation with a frequency of 6.57‰. Among the mutants verified in M3 generation, the frequency of leaf mutation was highest (2.22‰), followed by seedling height (1.74‰) and abiotic stress tolerance mutant (1.47‰). Nineteen characteristic mutations, including a big group of abiotic stress tolerant mutants such as herbicide resistant, salt tolerance and drought tolerance were identified at this stage. By observation of rice growth characteristics at different developmental stages, another 220 mutants have been isolated and verified in the M3 generation with the mutant frequency of 53.9‰ covering about 28 mutant taits. Among those identified, the highest frequency were obtained for appearance of brown rice mutant with 18.37‰ followed by panicle mutant with 13.47‰ and grain mutants with 9.06‰, respectively. All the mutants screened above were suitable for gene function analysis and for utilization in agronomy.

Near-infrared reflectance spectroscopy was used to address the genetic potential for 990 rice lines for 26 quality traits. The predicted genotypic values for quality traits were calculated using the Mahalanobis distance method and used to measure the genetic similarities among rice varieties. To make the core collection, Manhalanobis distance was employed to calculate the genetic distance among the accessions, and the hierarchical clustering method was used to group the accessions, accompanied by sampling method under the pre-concerted sample proportion (i.e., the ratio of accessions in the core collection to those in the initial population). In this experiment, 24 core collections were developed by using eight hierarchical clustering methods, combined with random, preferred and deviation sampling at a sample proportion of 15% (i.e., 149 for the 15% core collection). These core collections were compared with others constructed at sample proportions of 10% and 20% (i.e., 99 for the 10% core and 198 for the 20% core, respectively). In addition, a trend at increasing sample proportion from 5% to 60% showed that core collection development could be achieved at a sample proportion range of 10–25%. Further results revealed that deviation sampling strategy in combination with the single linkage method retained the greatest degree of genetic diversity of the initial collection. The core collection developed using a sample size of 15% retained the highest degree of diversity, and was stable for all the cluster methods and, hence, the best in developing a core collection of rice quality traits.

The analysis of temporal patterns of genetic effects for thousand-seed weight (TSW) and oil content (OC) in rapeseed was conducted at five different seed development times using unconditional and conditional genetic models for diploid seed quantitative traits. Phenotypic means among generations and seed development times in 2 different years revealed considerable variation for both TSW and OC. The expression of genes from diploid embryo, cytoplasmic and maternal plant genetic systems were all found to be important for the F1 generation, with maternal effects playing a more prominent role for both traits at most times. The conditional analysis indicated that the stage-specific gene expression from the maternal plant was influenced by environment. Higher magnitudes of additive and cytoplasmic effects were observed for both traits. Narrow-sense heritability was high for both traits at all developmental times with maternal heritability being more prominent at most times. Genetic correlations between TSW and OC were mostly negative over developmental times.

Using a newly developed mapping model with endosperm and maternal main effects and QTL environment interaction effects on quantitative quality traits of seed in cereal crops, the investigation of quantitative trait loci (QTLs) located on triploid endosperm and diploid maternal plant genomes for protein content and lysine content of rice grain under different environments was carried out with two backcross (BC1F1 and BC2F1) populations from a set of 241 recombinant inbred lines derived from an elite hybrid cross of Shanyou 63. The results showed a total of 18 QTLs to be associated with these two quality traits of rice, which were subsequently mapped on chromosomes 2, 3, 5, 6, 7, 10, 11 and 12. Three of these QTLs were also found havingQTL environment interaction effects. Therefore, the genetic main effects from QTLs located on chromosomes in endosperm and maternal plant genomes and their QTL environment interaction effects in different environments were all important for protein and lysine contents in rice. The influence of environmental factors on the expression of some QTLs located in different genetic systems could not be ignored for both nutrient quality traits.