Relationship Between Milled Rice Protein Content And Rice Quality Changes

The quality of rice,especially the cooking and eating quality,has become a key limiting factor for the sustainable development of rice production in China.The requirement of rice development is not only limited to the pursuit of high yield,but we should also pay more attention to its quality.As the main character of rice quality,protein is an important aspect of improvement in rice quality,which can not be ignored,but the relevant research is relatively weaker,the effects of protein on the quality of rice and its mechanism have been controversial.In this study,a series of near-isogenic lines introduced into G1 gene and sdl gene and six conventional indica and japonica cultivars were used as the test materials,and we set up different grain fertilizer treatments to analyse the yield,nitrogen translocation,soluble protein,nitrogen metabolism enzyme activity and rice quality.In particular,the effects of G1 gene and sdl gene on protein and its components,and the relationship between protein and rice quality changes was discussed to accumulate necessary theoretical understanding for the improvement in rice quality.Main results are as follows:1.There was a significant difference in yield between different near-isogenic lines.The introduction of G1 gene lead to the decrease in the effective panicle number,1000-grain weight and yield,but did no significant effect on grain number per spike and seed setting rate.The introduction of sdl gene reduced the effective panicle number to a certain extent,but increased the number of grains per ear and 1000-grain weight significantly,seed setting rate performed better and showed a higher level of yield.Appropriate grain fertilizer level had a certain effect on increasing production,mainly increasing the grain-filling ratio.Higher grain fertilizer level was detrimental to the improvement in seed setting rate,decreasing yield.2.Sdl gene and G1 gene had some influence on the protein content of rice.The introduction of G1 gene reduced the nitrogen and nitrogen ratio of stem and leaf,fallingin soluble protein content of grain and leaf and grain nitrogen metabolism enzyme activity simultaneously,which significantly reduced the total rice protein content.At the same time,analysis of the protein components content showed that the expressing of G1 gene reduced the content of each protein component,in which the highest content of gluten protein changed the most significantly,while the reduction of albumin,globulin and gliadin were relatively smaller.The introduction of sdl gene increased the nitrogen content of stem and leaf,but the nitrogen translocation ratio of stem and leaf decreased,and the soluble protein content of grain and leaf and the activity of grain nitrogen metabolism enzyme also much lower,thereby further reduced the protein content.The results of the protein components also showed the same trend.In a word,simultaneously introduced the sdl gene had the effect on enhancing the expression of G1 gene.3.The introduction of Sdl gene and G1 gene had some influence on rice quality.The introduction of G1 gene resulted in the improvement in processing quality and deterioration of appearance quality and there was no significant effect on amylose and gel consistency.But the starch gelatinization properties(RVA)had certain changes,peak viscosity,hot viscosity and breakdown increased significantly,peak time and pasting temperature increased,while cool viscosity,cnsistence and setback decreased.The content of free amino acid in the kernel also significantly decreased,taste value improved remarkably.In general,the introduction of G1 gene had the performance of improving rice quality.On the other hand,the simultaneous introduction of sdl gene significantly enhanced the improvement of the above traits,and the amylose content decreased,gel consistency become longer oppositely,so it was noted that sdl gene can help improve the quality of rice.4.There was a close relationship between rice protein content and rice quality.The analysis of near-isogenic lines showed that there was no significant correlation between protein content and amylose content,while highly significant negative association between protein and gel consistency was observed,and there was extremely significant negative correlation between protein and taste value similarly,all the above indicated a significant trend that protein content deteriorated the rice cooking and eating quality.The results of different types of cultivars also showed that there was no significant correlation between total protein and amylose content in conventional indica and japonica cultivars,but significantly negatively correlated with gel consistency,meanwhile,the relationship between protein content and taste value was significant negative correlation,and protein content had significant positive correlation with consistence and setback.The analysis of conventional indica and japonica varieties also showed that there was a significant positive correlation between protein content and processing quality,which indicated that the commercialization of rice improved,but the palatability of rice reduced.5.The application of grain fertilizer had a significant effect on rice quality.After applying grain fertilizer,the nitrogen content of stem and sheath,leaf and grain increased,having the same effect on the nitrogen output ratio of vegetative organs after anthesis,consequently,free amino acid content increased,which significantly promoted the protein content of rice,and the higher the level of grain fertilizer was,the greater the increase would be.The effect of grain fertilizer on increasing the protein was far more than that of the low protein gene G1.The content of four protein components increased significantly with the increasement of nitrogen application rate.Moreover,grain fertilizer could improve the processing quality and appearance quality,the amylose content decreased,but gel consistency became shorter significantly.Peak viscosity,hot viscosity,breakdown,cool viscosity and taste value decreased significantly.6.The sequences of GS,GOT and GPT activities were that background material Sasanishiki(PO)was the highest,material P2(introduce the G1 gene)was the second,material P1(simultaneous introduce the sdl gene and G1 gene)was the lowest,and such trend presented the same performance under different levels of grain fertilizer as protein content.The results showed that the introduction of G1 gene significantly reduced the activity of the activities of nitrogen metabolism enzyme,while the sdl gene had an upward trend in the effect of G1 gene.The application of grain fertilizer also significantly increased the GS,GOT and GPT activities of different grain position.