| Gluten quality is an important factor determining wheat grain processing characteristics.Simultaneous improvement of wheat grain yield and gluten quality is an inevitable choice to meet China’s growing food demand,ensure national food security,and achieve the agricultural development goal of“stabilizing grain,increasing production and improving quality,increasing efficiency”.To improve wheat gluten quality,it is necessary to increase grain protein content to improve wet gluten content and to maintain a high gluten index to ensure gluten strength.However,the negative correlation between grain yield and protein content and the complex effects of genotype-environment interaction on gluten index limit the realization of the goal of simultaneous improvement of wheat grain yield and gluten quality.Nitrogen is a critically nutrient element affecting wheat yield and gluten quality.Water deficit leads to a significant decrease of nitrogen availability in hill dryland of southwest China,the relationship between pre-anthesis,post-anthesis nitrogen accumulation as well as post-anthesis nitrogen translocation and simultaneous improvement of dryland wheat yield and gluten quality is still unclear,the regulation effect of nitrogen fertilizer application on the simultaneous improvement of yield and gluten quality of dryland wheat with different yield and gluten quality types also needs further study.For this reason,11representative wheat varieties in this study were used as experimental materials to discuss the relationships between nitrogen accumulation,translocation,post anthesis photosynthesis and grain yield,gluten quality of different type wheat in 2018-2021 by using a randomized block design,so as to reveal the critically agronomic traits and nitrogen efficiency characteristics of high yield and good quality wheat.A field experiment was conducted from 2019 to 2021 with a two factor split plot design to study regulatory effect of nitrogen fertilizer application on simultaneous improvements of grain yield and gluten quality of different type wheat.The main factors were wheat varieties with different grain yield and gluten quality types;and the side factors were three nitrogen fertilizer application levels,including high nitrogen(HN,225kg N ha-1),medium nitrogen(MN,150 kg N ha-1),and low nitrogen(LN,75 kg N ha-1).The main results were as follows:1.The grain weight per spike,nitrogen accumulation at maturity and nitrogen translocation efficiency were the critically agronomic traits and nitrogen efficiency-related indicators associated with simultaneous improvement in grain yield and gluten quality of dryland wheat.In 2018-19,2019-20 and 2020-21 cropping seasons,grain weight per spike accounted for 49.2%,72.3%and 54.5%genetic variations of yield,respectively,with the average of 58.7%,which was higher than that of fertile spikes（39.2%）and thousand-grain weight（17.0%）.Meanwhile,grain weight per spike and nitrogen accumulation at maturity explained 43.8%,59.7%,23.7%and 45.6%,33.4%,23.7%genetic variations of grain protein content,with the averages of 42.4%and 49.5%,respectively,which were higher than that of nitrogen harvest index（6.2%）.Therefore,the genetic variations of grain yield and wet gluten content of high-yield and high-gluten variety CY25,high-yield and low-gluten variety MM51,low-yield and high-gluten variety CM39 and low-yield and low-gluten variety SM482 can be explained by the differences in grain weight per spike and nitrogen accumulation at maturity.Furthermore,the high grain yield and wet gluten content of CY25were mainly related to the increased grain weight per spike and nitrogen accumulation at maturity caused by the improvement of thousand-grain weight.In addition,gluten index<90%significantly reduced sedimentation value,and the gluten index was affected by the interaction between genotype and environment.Compared with 2018-19 cropping season,the rainfall in 2019-20 cropping season significantly reduced by 53.8%,while nitrogen accumulation at anthesis improved by 14.0%,nitrogen translocation efficiency and gluten index increased by 3.0 and 13.0 percentage points,respectively.In particular,the gluten index and sedimentation value of high-yield and high-gluten variety CY25 increased by 22.0percentage points and 44.0%,respectively.In addition,in 2019-20 cropping season,the significant increase in flag leaf area and leaf area index of NM101 increased grain number per spike,nitrogen accumulation at anthesis and nitrogen accumulation at maturity,and maintained a high gluten index,thereby simultaneously improved its grain yield and sedimentation value.In contrast,in 2018-19 cropping season,low fruiting efficiency of NM101 decreased grain number per spike,delayed nitrogen translocation,resulting in a significant decrease in gluten index.These results indicated that the cooperative effects among the decrease in post-anthesis nitrogen accumulation caused by increased nitrogen accumulation at anthesis,increase in sink nitrogen demand caused by increased grain number per spike and accelerated aging caused by drought stress accelerated post-anthesis nitrogen translocation process,thereby improved nitrogen translocation efficiency and gluten index.2.Leaf area and net photosynthetic rate of flag leaf were the critical photosynthesis factors affecting simultaneous improvement of dryland wheat grain yield and gluten quality.In 2019-20 cropping season,the net photosynthetic rate and dry matter translocation of stem from 10 to 40d after anthesis of MM51 with erect flag leaf increased by 5.8%and 23.1%,respectively,compared with the average value;while the thousand-grain weight and grain protein content decreased by 2.3%and 0.8 percentage points,respectively.The nitrogen content and net photosynthetic rate of flag leaf of“stay-green”variety CM34 decreased by0.2 percentage points and 5.5%,respectively,while the thousand-grain weight increased by9.5%,grain protein content and gluten index decreased by 2.0 and 40.0 percentage points,respectively.These results indicated that the improvement of light interception efficiency and the extension of post-anthesis photosynthesis time of high-yield and low-gluten varieties MM51 and CM34 improved their dry matter translocation and source carbon supply capacity.However,insufficient source nitrogen supply capacity reduced their grain protein content,and the extension of grain filling reduced the gluten index of CM34,making it difficult to simultaneously improve wheat grain yield and gluten quality.In contrast,in 2019-20 and2020-21 cropping seasons,the water use efficiency and electron transport rate of the high-kernel weight variety CY25 increased by 41.4%and 16.9%,respectively,compared with the average value,the net photosynthetic rate increased by 16.1%and 18.5%,respectively,and the wet gluten content increased by 7.2 and 6.6 percentage points,respectively.In 2019-20 cropping season,the nitrogen content and net photosynthetic rate of flag leaf of the high flag leaf area variety NM101 decreased by 0.3 percentage points and2.7%,respectively,compared with the average value,while dry matter translocation of stem from 10 to 40d after anthesis and sedimentation value increased by 30.8%and 19.7%,respectively.Therefore,the increase of net photosynthetic rate of flag leaf improved grain filling process,thereby simultaneously increased wheat yield and wet gluten content.The increase of flag leaf area promoted post-anthesis nitrogen translocation,thereby simultaneously increased wheat yield and sedimentation value.3.Increasing nitrogen fertilizer application mainly regulated simultaneous improvement of dryland wheat grain yield and gluten quality by improving nitrogen accumulation at anthesis and grain number per spike.Analysis of variance results showed that nitrogen accumulation at anthesis,nitrogen translocation efficiency and grain number per spike were mainly affected by nitrogen fertilizer effect,followed by genotype effect.In 2019-20 and2020-21 cropping seasons,compared with low nitrogen treatment,grain number per spike under medium nitrogen and high nitrogen treatments increased significantly by 2.4%,7.1%and 8.7%,10.9%,respectively,and the yield increased significantly by 11.6%,16.3%and16.1%,23.2%,respectively,however,there was no significant difference in grain number per spike and yield between medium nitrogen and high nitrogen treatments（P>0.05）.The wet gluten content significantly increased by 3.8,6.7 and 3.7,5.2 percentage points,respectively,and the sedimentation value significantly increased by 35.9%,43.0%and35.7%,47.4%,respectively.The difference of wet gluten content among different nitrogen treatments was significant（P<0.05）,but the sedimentation value under high nitrogen treatment was significantly higher than that under medium nitrogen treatment only in2020-21 cropping season（P<0.05）.These results indicated that increasing nitrogen fertilizer application could significantly increase grain yield and wet gluten content of dryland wheat,while the improving effect of 225 kg N ha-1nitrogen application rate on wet gluten content was greater than that on grain yield,compared with 150 kg N ha-1nitrogen application rate.Compared with medium nitrogen treatment,high nitrogen treatment significantly increased the yield of low-yield and high-gluten variety CM39 and the sedimentation value of high-yield and low-gluten variety CM34 in 2019-20 cropping season;and the grain number per spike of CM39 improved by 15.8%,and the wet gluten content of CM34 increased by 6.9 percentage points.In 2020-21 cropping season,the gluten index of CM66 and MM51 under high nitrogen treatment significantly reduced by 16.0 and 14.0percentage points,respectively,while CY25 significantly increased by 3.9 percentage points.These results indicated that high nitrogen treatment had a greater regulation effect on the simultaneous improvement of wheat grain yield and gluten quality to wheat varieties with strong nitrogen uptake capacity before anthesis,and could increase the gluten index of wheat varieties with low gluten index,but might decrease the gluten index of wheat varieties with high gluten index.In summary,the key to improve yield and gluten quality of dryland wheat was to increase grain weight per spike and nitrogen accumulation at maturity,which can be achieved by genotype selection of high thousand-grain weight or high flag leaf area and leaf area index.At the same time,increasing nitrogen accumulation at anthesis and post-anthesis nitrogen translocation efficiency improved gluten index,thereby simultaneously improved wheat yield and sedimentation value.Increasing nitrogen fertilizer application rate improved grain number per spike,nitrogen accumulation at anthesis and nitrogen translocation efficiency,thereby simultaneously improved wheat yield and gluten quality.However,genotype is the main factor affecting the simultaneous improvement of grain yield and gluten quality of dryland wheat,compared to nitrogen fertilizer application. |
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