Responses Of Wheat Grain Yield And Protein Content To Genotypes Under Different Water And Fertilizer Conditions

The simultaneous improvement of protein content(PC)and grain yield(GY)in wheat under low water and fertilizer input management enables the development of resource-use efficient varieties that combine high grain yield potential with desirable end-use quality.However,the complex mechanisms of genotype,management,and growing season,and the negative correlation between PC and GY complicate the simultaneous improvement of PC and GY under low water and fertilizer input management.To answer the response mechanism of GY and PC to genotype,management and growing season in wheat,specify wheat cultivars with stable expression of high GY and high PC,so that facilitate the development of high-yielding and high-quality wheat varieties under low water and fertilizer input management,which is critical for sustainable food and nutrition security,this study used 209 wheat varieties,including strong gluten,medium-strong gluten,medium gluten,weak gluten,winter,semi-winter,weak-spring,and spring types,that had been promoted from the 1980s to the 2010s.Field trials were conducted by randomized complete-block design with two management treatments(conventional management and low water and fertilizer input management)during two growing seasons(2018-2019 and 2019-2020),and GY,PC,plant height,chlorophyll content,canopy temperature and Normalized Difference Vegetation Index(NDVI)were observed.in addition,allelic genotyping,performed using Kompetitive Allele Specific Polymerase Chain Reaction(KASP)technology,found 69 types of GY-PC allelic combinations in the tested materials.The results showed that:(1)Multi-environment analysis of variance showed that genotype had the greatest effect on GY and PC compared with growing season and management,and GY and PC were highly heritable.According to the correlation analysis,GY and PC were significantly negatively correlated in different growing season s and under different management.Under the traditional management,the GY was higher,while under the low water and fertilizer management,the PC was higher.In the growing season with more precipitation,the GY was higher,and in the growing season with higher temperature,the PC was higher.(2)According to the 3-sigma rule of the normal distribution the PC of strong gluten wheat was higher than medium gluten wheat,and the wheat cultivation in China pays less attention to protein content than other countries.The GY of wheat cultivars Liangxing 66 and Xinmai 18 were stable among the top 15.87%of all tested materials with high GY,and their PC reached mean levels under low water and fertilizer input management,but also stably expressed high GY and high PC under conventional management.(3)Compared with the allele combinations of high GY and low PC,the chlorophyll content in flowering stage and middle and late grain filling stage,and the NDVI in flowering and grain filling stage of the allele combinations of high yield and high protein content were higher,but the plant height at flowering stage,the chlorophyll content in early stage of grain filling stage,and the canopy temperature in the middle and late stage of grain filling stage were lower.Compared with the allele combinations with low GY and high PC,the chlorophyll content and NDVI in flowering stage and grain filling stage were higher,but the plant height in flowering and grain filling stage and the canopy temperature in grain filling stage were lower.(4)It was found genetically that,Liangxing 66 and Xinmai 18 carried favorable alleles for GY related genes,including TaSus1-7A,TaSus1-7B,TaGW2-6A,and TaGW2-6B,with Hap-1/2 of TaSus1-7A being known to be stably expressed.Meanwhile,both elite cultivars also carried favorable alleles for PC,including the allele Glu-B3b/d/g/i of Glu-B3.(5)Combining with structural equation model,it was found physiologically that,they also showed high NDVI value at flowering stage,which was a phenotypic trait significantly related to high GY and high PC.Therefore,Liangxing 66 and Xinmai 18 can be used as parental elite materials in breeding.Based on the above results,the following conclusions could be reached:(1)Wheat GY was more susceptible to management and growing seasons and their interactions than PC.(2)Reasonable low water and fertilizer input management can achieve high GY and high PC and improve water and nitrogen use efficiency.(3)For wheat varieties with medium PC,it is easier to obtain lower GY and higher PC in the growing season with high tem perature stress in grain filling stage.(4)Wheat GY and PC depend on genotypes,which lays a foundation for screening good varieties and identifying favorable genotypes.(5)Although the PC of wheat varieties in China is relatively low now,there are also varieties with high GY and high PC for efficient utilization of resources.In summary,the results of the study can provide an important scientific basis for green sustainable development and quality and efficiency of agriculture.