The analysis of basic properties of the low glutelin rice for new characteristic rice variety development in Niigata

In rice, the characteristic of low glutelin is controlled by a dominant gene, Lgc1. There have been few studies that investigated the influence of Lgc1, except in term of seed storage protein composition. Additionally, the effects on this gene on taste and processing characteristics have not been clarified. To investigate specific gene pleiotropy, it is effective to compare isogenic lines with a common genetic background. In this study, co-dominant DNA markers for PCR were developed for the breeding of isogenic lines. Two near-isogenic line pairs were developed with these DNA markers. Furthermore, to investigate the influence of Lgc1, basic agronomic characteristics, processing characteristics of boiled rice and rice flour were examined. A co-dominant DNA marker for PCR was developed for a breeding of the isogenic lines for Lgc1. Two near isogenic line pairs were successfully developed with these DNA markers. Between near-isogenic lines with different protein, the low glutelin type was significantly heavier in terms of 1000-kernel weight of brown rice than its wild type. The low glutelin type was also superior to its wild type in terms of quality of appearance of the brown rice. However, notable differences were not shown in days to heading, days to ripening, culm length, panicle length, grain yield, shape of brown rice, and protein content of brown rice. From these results, it was concluded that the two sets of near-isogenic line pairs developed in this study should be useful for investigation of the pleiotropism of the Lgc1 gene. In order to investigate the effects of changes in the endosperm protein composition due to the low glutelin gene Lgc1, the processing characteristics of boiled rice and rice flour were investigated using two sets of near-isogenic line pairs for the Lgc1 locus. On measurement of gelatinization physical properties, we found that final viscosity and consistency were significantly higher in low glutelin lines. On physical property measurement with boiled rice, surface stickiness was significantly decreased in the low glutelin lines, and a significant decrease was seen in the balance of hardness to stickiness. On water absorption of the polished rice grains at 15degC, a significant difference was not observed between the low glutelin lines and normal protein composition lines. In this study, the low glutelin lines showed higher amylose content than normal protein composition lines. Therefore, the differences between low glutelin lines and normal protein composition lines could not be determined based on protein composition alone. However, these differences are the cause of the low palatability of boiled rice and are responsible for the processing characteristics of flour made from low glutelin cultivars possessing the Lgc1 gene. It became clear that the low glutelin due to the Lgc1 gene causes a decline of the tenacity of the outer layer of boiled rice. This characteristic may usually cause declines of the taste for boiled rice. But not sticky rice is suitable for sushi or pilaf. Further examination of utility value of the low glutelin rice is possible in using these near isogenic line pairs.