Study On Different Characteristics Of Eating Quality Of Transgenic Rice With Wx Gene Under Different Cultivation Conditions

As the most important part of rice quality,rice taste quality has been paid more and more attention with the improvement of social material level.Starch and protein,as the main components of rice grains,have important effects on the taste quality of rice.Wx gene is the main gene controlling amylose synthesis in rice grains and is generally considered to be the key gene affecting food quality.In the past studies,Wx gene has been studied in detail on genetics and other aspects,but the effects of Wx gene on rice eating quality are relatively simple,mainly focusing on starch,ignoring the effects of cultivation environment and other components of grain on eating quality.Therefore,in this study,six different Wx allelic materials with the same genetic background were used to study their yield,grain composition,food quality and physicochemical properties of main components of grain under different cultivation conditions,so as to further explore the effects of Wx gene on rice food quality under the conditions of nitrogen fertilizer,sowing date and water.The main research results are as follows:1.Increased nitrogen application increased the number of panicles and yield,and decreased the number of grains per panicle and seed setting rate,but ultimately contributed to the increase of yield.With increased nitrogen application,Wx^la increased2.32 t ha^-1,while Wxb increased only 0.15 t ha^-1.Delaying sowing date increased the number of effective ears,and Wxlv increased by 151.2×10⁴ ha^-1 in D2 sowing date.The grain number per panicle and seed setting rate were affected by Wx gene difference.Drought in filling period decreased the effective panicle number and seed setting rate,and decreased the yield.The yield of Wx^b and Wxⁱⁿ was little affected by cultivation measures,but the yield composition changed.Grain phenotype was less affected by cultivation conditions and Wx gene.2.Wx gene controls the activity and content of GBSSI,but it is affected by cultivation measures.The activity and content of GBSSI increased first and then decreased after anthraculation,showing a strong consistency.The activity and content of GBSSI were Wx^lv>Wxⁱⁿ>Wx^b>Wx^la>Wx^mp>wx.Increased application of nitrogen fertilizer was beneficial to increase the activity and content of GBSSI.The expression level of GBSSI was increased at 7 days after anthesis,while the expression level of GBSSI was increased at 14 days after anthesis.Drought treatment can reduce the activity and content of GBSSI to a certain extent.3.wx has the lowest amylose content,accounting for only 2.3%-3.0%of the chemical composition of white rice,while Wxlv has the highest amylose content,reaching20.7%-23.4%.The content of amylose was Wx^lv>Wxⁱⁿ>Wx^b>Wx^la>Wx^mp>wx,which was consistent with the activity and content of GBSSI.Cultivation measures have influence on starch content and protein content.The increased application of nitrogen fertilizer promoted the synthesis of protein,and the total protein content increased by 0.12%-2%.The contents of globulin,alcohol-soluble protein and gluten in protein components increased.The effect of sowing date on protein was influenced by Wx gene difference.Drought in grouting period decreased the content of total protein and alcohol-soluble protein.The content of albumin was less affected by culture measures and Wx gene difference.The RVA characteristic value,curve and cooking taste value of different Wx showed great difference.The Wx^la and Wx^mp of lower amylose had higher peak viscosity,disintegration value and viscosity,lower digestion value,gelatinization temperature and hardness,and higher cooking and eating quality.Wxⁱⁿ and Wx^lv with high amylose showed opposite performance and low taste value.Increased application of nitrogen fertilizer and drought during filling period decreased the cooking taste value,which mainly showed that the elasticity,appearance and taste scores after cooking were decreased,and hardness was increased.Sowing date had little effect on eating quality4.There was little difference in grain morphology and obvious difference in grain transparency among different Wx,which may be mainly caused by different amylose content.The grain size of rice flour is affected not only by the difference of starch components,but also by other inclusions such as protein.The starch granules with high amylose content may have larger starch granules.The grain structure of rice starch is A-type crystal.Wx^lv rice flour and starch have higher crystallinity,starch particle structure is more stable,high degree of polymerization,not easy gelatinization.The DTG profiles of Wx^mp rice flour and starch showed earlier degradation,lower peak temperature and faster degradation rate,which was consistent with the characteristic values of RVA.The differences between rice flour and starch indicated that the contents of protein,lipid and amylose affected the turbidity,expansion and RVA of starch in water.The protein properties of different Wx genes were different.Microscopically,the protein surfaces of Wxmp and wx are delicate and smooth.Wx^b has smaller particle size,higher absolute value ofζpotential,higher disulfide bond and less free sulfhydryl group.The protein colloid is stable,which is not favorable for protein gelation,and the gel network formed by protein gelation will affect the water absorption and gelatinization of starch.Protein solubility wx>Wx^mp>Wx^b>Wxⁱⁿ>Wx^la>Wx^lv in neutral solution.The higher the solubility is,the weaker the hydrophobic effect is,and it is not easy to adhere to the surface of starch,which has less influence on starch gelatinization.The stronger UV absorption of Wx^lvprotein indicated that more hair group was transferred to the surface of the protein,and the protein had stronger hydrophobic effect.Moreover,the fluorescence intensity is low,which may be due to the winding and aggregation of protein chains,which is easier to form protein gel network.In conclusion,different cultivation conditions have different effects on rice taste.The application of nitrogen fertilizer decreased the eating quality of rice.The activity and content of GBSSI increased under the condition of increased nitrogen application,which resulted in the increase of amylose content in rice.In addition,grain gluten and alcohol-soluble protein content also increased.All these influence the gelatinization of starch,resulting in the decrease of peak viscosity and disintegration value of starch,and ultimately inhibit the gelatinization characteristics of starch and reduce the taste quality of rice.Drought treatment at sowing and filling stages had little effect on rice taste.According to the results of this experiment,the effect of Wx gene on rice eating quality was greater than that of cultivation conditions,and the main reason was that Wx genes affected amylose content of rice by influencing GBSSI.In order to further analyze the mechanism of Wx gene on rice taste quality.We analyzed the differences in the structural and functional properties of starch and protein under different Wx genes and found that Wx gene plays an important role in the physicochemical properties of starch and protein.