Differences In Grain Starch Properties Of Wx Gene Near-Isogenic Lines Rice And Their Response To Late-Stage Nitrogen Fertilizer

Social development and economic progress put forward new requirements to the rice planting industry.Taking simultaneous development of the improvement in rice yield and rice quality into account has become the main direction of rice production in the new period.Wx gene is one of the key genes to control the quality of rice.Its analysis in the domain of genetics and molecular biology is thorough,but the expression of Wx gene has not been effectively carried out under the condition of population.In this study,we used different Wx genotype rices near isogenic lines(Wxa?Wxin?Wxb?wx)as test materials,and different nitrogen treatments were set up during the rice seeding period.To observe the starch characteristics of different Wx genotype rices and its response to late-stage nitrogen fertilizer,and try to analyze the environmental effect and its formation mechanism of rice quality from the perspective of gene expression and environment interaction,and obtain accurate understanding of the rice quality affected by late-stage fertilization,and provide the necessary theoretical basis for high quality cultivation control measures.The main results are as follows:1.The yield of Wx genotype rice was the same trend as Wxa>Wxin>Wxb>wx genotypes.At the same time,the response of each genotype to late-stage nitrogen fertilizer was different.The yield of Wxa and Wxin genotypes increased significantly as the late-stage nitrogen fertilizer increased.The effective panicle number and 1000-grain weight of Wxa genotype rice were higher and the seed setting rate was relatively low,and the number of grains per spikelet was relatively higher in Wxin and wx genotypes,and the Wxb genotype ranked the lowest.Wxa and Wxin genotypes had higher dry matter accumulation but that of Wxb genotype was much lower.A small amount of fertilization could cause a significant increase in indica Wxa genotype rice production,while japonica Wxb genotype rice was relatively insensitive to late fertilization.2.Different Wx genes were introduced into waxy rice(wx genotype),which significantly increased the rate of brown rice and polished rice.The late-stage application of nitrogen fertilizer improved the processing quality and appearance quality of rice to a certain extent.The rice amylose content and gel consistency significantly differed when different Wx genes were inserted into waxy rice,presenting remarkable characteristics of Indica and Japonica varieties.As the amount of fertilizer applied was increased,apparent amylose content increased,gel consistency decreased,breakdown and peak viscosities dropped,and setback viscosity and peak time increased.Moreover,cooking quality showed a significant decline during the period,especially under low-level nitrogen fertilizer application.The Wxa and Wxin genotypes were more sensitive to late-stage fertilization than the Wxb and wx genotypes.3.After the Wx gene was introduced,the volume percentage of pint-sized starch granules and the medium-sized starch granules increased,but that of the large-sized starch granules decreased.Starch granule surface area and the number of the percentage showed non-waxy materials have a higher proportion of pint-sized starch granules than waxy materials,and lower proportions of medium-sized and large-sized starch granules.There was a significant negative correlation between the volume percentage of pint-sized starch granules and the gelatinization characteristics.The volume percentage of large-sized starch granules was positively correlated with the characteristic values of each gelatinization.With the increase of the amount of nitrogen applied in the later stage,the volume,surface area and quantity percentage of the pint-sized starch granules of each material showed an upward trend,and the trends of medium-sized starch granules and pint-sizedstarch granules were opposite.The increase in the size of the pint-sized starch granules and the reduction of the medium starch granules resulted in a decrease in the amount of heat required for starch gelatinization and a drop in the gelatinization heat.4.Amylopectin structure varied significantly in different genotypes of the Wx gene,and the degree of branching was as follows:wx>Wxb>Wxin>Wxa.This result indicated that closeness to Indica corresponds to less short chain proportion.Starch crystallinity and swelling potential also changed accordingly.The amylose content significantly negatively correlated with the breakdown viscosity and gelatinization temperature but positively correlated with the cool paste viscosity,setback viscosity,consistence viscosity,and peak time,while the rule of amylopectin branching degree was the contrary.The late-stage nitrogen fertilizer application resulted in decreased short chain proportion of Indica Wxa material and increased long chain proportion of Japonica Wxb material,which consequently reduced the starch branching degree.Starch crystallinity and swelling potential were negatively correlated with amylose content but significantly positively correlated with amylopectin branching degree,decreasing with the increase of late-stage nitrogen fertilization.5.The expression level of Wx gene in different genotypes was similar,and the expression of Wx gene was increased in the superior grains,and reached the peak at about 10 days,and decreased at 15 days after heading,while the inferior grains were still in the process of increasing expression at 20 days after heading.There was a significant positive correlation between GBSS activity and Wx gene expression.The expression of Wxa and Wxin gene was significantly increased with the increase of late-stage fertilization level,the expression of wx gene was much low,and it was relatively insensitive to late-stage fertilization.The activity of GBSS was correspondingly changed.