Abstract:

As a staple cereal crop in the world, rice feeds more than 50% of the world population. The improvement for rice quality including protein content and kinds of amino acid contents is an important work to meet the demands of a growing population. The genetic analysis on rice indicate that the inheritance of nutrient quality traits is complex, which involve the genetic effects from the triploid endosperm nuclear genes and the diploid maternal plant nuclear genes, being further partitioned into additive and dominance effects, and their genotype × environment (GE) interaction effects. So far, the magnitude and prevalence of interactions between quantitative trait loci (QTL) of the triploid endosperm genome or diploid maternal genome for rice traits are still largely unknown. Therefore, it is necessary to study the genetic main effects and GE interaction effects of the QTL from different genomes across environments. Investigations to identify QTL governing histidine (His) and arginine (Arg) contents of rice were conducted using the newly developed QTL mapping method including endosperm and maternal main effects and their GE interaction effects on quantitative traits of seed in cereal crops. Two backcross populations, which were a set of 241 RILs derived from an elite hybrid cross of ‘Shanyou 63’ crossed with ‘Zhenshan 97’ (BC1F1) or ‘Minghui 63’ (BC2F1), were used in two environments. The results showed that significant differences were found between the two parents for both quantitative quality traits. His and Arg of rice for Zhenshan 97 were higher than those for Minghui 63. The distributions of phenotypic values for His and Arg in BC1F1 (RILs × P1) and BC2F1 (RILs × P2) populations revealed normal distributions approximately. Both backcross populations also showed varying distributions in 1999 and 2000, implying that both amino acid traits were subjected to the modification by environments. A total of ten QTL associated with His content were mapped on chromosomes 1, 2, 3, 6, 7, 10, 11, and 12. Significant additive effects (ae and de) of QTL from diploid maternal plant and triploid endosperm were detected for all of these QTL. Two of them were also found to have visible endosperm dominance main effects and five QTL had significant environmental interaction effects. A total of eight QTL associated with Arg content of rice were mapped on chromosomes 2, 3, 5, 6, 7, 10, 11, and 12. Significant additive main effects of QTL from both genomes were all detected for all of these QTL. Two of them were also found to have visible endosperm dominance main effects and two QTL had significant environmental interaction effects. The proportions of phenotypic variation attributable to the total genetic main effects and GE interaction of QTL were 0.147 and 0.055 for His and 0.160 and 0.018 for Arg, respectively. These results showed that the control for His and Arg contents of rice was distributed over several chromosomes and the environmental interaction effects were also important for the performance of these quality traits.

Key words:

Rice (Oryza sativa L.), Quantitative trait loci (QTL), Histidine, Arginine, Endosperm, Maternal plant, Environmental interaction