Analysis of Factors Affecting Seed Protein Compositions and Protein Contents in Rice of Seed-Protein Mutant Cultivars under Different Cropping Seasons

Abstract

The essential points for controlling the digestible protein content (DP) of rice grain at low levels in seed-protein mutant rice cultivars (SPMR) were investigated. A low-glutelin cultivar 'LGCsoft', a 26-kDa globulin-deficient low-glutelin cultivar 'LGC-Jun', and a normal-type cultivar 'Nihonmasari', were cultivated for 8-9 cropping seasons over a period of 4 years. Factors affecting seed protein composition and protein content in rice grain were analyzed. DP was affected by both the total protein content (TP) and the ratio of DP to TP in all cultivars. However, the effect of DP / TP on DP was greater in 'LGCsoft' and 'LGC-Jun' than in 'Nihonmasari'. A positive correlation between DP / TP and air temperature from 0 to 15 days after heading was observed in all cultivars. The highest correlation coefficient was observed from 0 to 10 days after heading in 'LGCsoft' and 'LGC-Jun', which was slightly earlier than in 'Nihonmasari'. Therefore, it is important to adjust the planting season to avoid high temperatures during the early ripening period for the cultivation of SPMR. TP affected DP more than DP / TP not only in 'Nihonmasari' but also in SPMR. A positive correlation was observed between TP and the nitrogen content of shoots at the heading stage, and a negative correlation was observed between TP and the percentage of ripened grains. These results indicate that shoot nitrogen status and percentage of ripened grains should be taken into account in planting and cultivation management plans.

Estimating the Protein Concentration in Rice Grain Using UAV Imagery Together with Agroclimatic Data

“…The characteristics of each cultivar, such as growth speed and the nutrient translocation from source to sink, are different. According to previous studies, the effect of cultivar difference is as great as that of fertilization [19]. It is necessary to obtain parameters specific to the cultivar based on MR analysis using GNDVI heading and SR grain-filling ; therefore, it is necessary to perform tests with multiple transplantation dates, as done in this study, to optimize the parameters of the GPC estimation model.…”

“…Rice with good eating quality is traded as brand rice, and improving the eating quality is seen as a way to enhance farmers' income. Thus, in Japan, there has been considerable basic research and numerous cultivation experiments attempting to control GPC in an appropriate way [16][17][18][19][20][21][22]. GPC is related to the firmness and stickiness of cooked rice (e.g., as the GPC decreases, cooked rice becomes sticky).…”

“…In addition, grain amylose content is also related to the eating quality of cooked rice, it has been revealed that grain amylose content is affected strongly by cultivar and temperature during grain-filling stage [21,22]. On the other hand, GPC is affected strongly by canopy nitrogen content and cultivar [19]. Thus, GPC is affected strongly by nitrogen fertilizer [19].…”

“…On the other hand, GPC is affected strongly by canopy nitrogen content and cultivar [19]. Thus, GPC is affected strongly by nitrogen fertilizer [19]. Among the factors that affect eating quality of cooked rice, GPC is a factor that could be controlled through proper fertilization management [24].…”