Discovery Of Key Genes Regulating Wheat Leaf Stomatal Traits And Their Superior Sites

Wheat is one of the three major food crops in the world.The stable and high yield of wheat is of great significance to ensure food security in China.Stoma is widely distributed on the surface of leaves,which is an important channel for gas and water exchange between plants and the external environment,and directly affects the photosynthesis and transpiration of plants.In our study,the relationship between flag leaf traits and stomatal traits of wheat and the relationship between stomatal traits and photosynthetic parameters were studied,and combined with genome-wide association analysis,in order to reveal the stomatal traits of wheat drought resistance and water saving and screen the genes related to stomatal traits.The main results of this study are as follows:1.A total of 204 wheat materials from major wheat areas in China and abroad were used as experimental materials.They were planted in the field and dry shed in the 2020-2021wheat season and 2021-2022 wheat season,and the flag leaf traits and stomatal traits of wheat were determined.Through variance analysis and pairwise comparison,it was found that drought had a certain effect on flag leaf traits and stomatal traits.The flag leaf traits in the two wheat seasons were different.In the 2020-2021 wheat season,the flag leaf length and flag leaf area of the dry shed decreased by 6.6%and 7.0%,respectively,compared with the field.In the 2021-2022 wheat season,the flag leaf length,flag leaf width and flag leaf area of the dry shed increased by 2.1%,4.9%and 6.9%,respectively.The performance of stomatal traits in the two wheat seasons was similar.In the wheat season of 2020-2021,the stomatal length and stomatal area under the dry shed decreased by 1.4%and 3.0%,respectively,and the stomatal density increased by 12.0%.In the wheat season of2021-2022,the stomatal length,stomatal width and stomatal area decreased by 9.1%,8.3%and 17.5%,respectively,and the stomatal density increased by 27.0%.The correlation between flag leaf traits and stomatal traits was analyzed.It was found that there was a significant positive correlation between flag leaf length and stomatal length,flag leaf width and stomatal width,flag leaf area and stomatal area in the two wheat seasons.There was a consistent change between flag leaf traits and stomatal traits,and a linear regression equation for these three pairs of traits was established,which could predict stomatal traits through flag leaf traits within a certain range.2.By measuring the photosynthetic parameters of the two groups of stomatal traits extreme materials,it was found that there were differences in photosynthetic parameters,among which stomatal conductance and instantaneous water use efficiency were significantly different.Multiple comparisons showed that the photosynthetic parameters of materials with large stomatal area and small stomatal density were higher than those with small stomatal area and large stomatal density in both environments.The correlation between stomatal traits and photosynthetic parameters was analyzed.In the field environment,stomatal length was positively correlated with transpiration rate and stomatal conductance,and the correlation coefficients were 0.371 and 0.366.The stomatal area was positively correlated with transpiration rate,and the correlation coefficient was 0.390.Stomatal density was negatively correlated with transpiration rate and net photosynthetic rate,and the correlation coefficients were-0.379.In the dry shed environment,stomatal length was positively correlated with transpiration rate and net photosynthetic rate,and the correlation coefficients were 0.364 and 0.422,respectively.In general,stomatal length was positively correlated with transpiration rate,net photosynthetic rate and stomatal conductance,and the correlation coefficients were 0.364,0.343 and 0.300,respectively.The stomatal area was positively correlated with transpiration rate and net photosynthetic rate,and the correlation coefficients were 0.321 and 0.314,respectively.Stomatal density was significantly negatively correlated with net photosynthetic rate and stomatal conductance,with correlation coefficients of-0.378 and-0.380.Stomatal density was negatively correlated with transpiration rate and intercellular CO₂concentration,with correlation coefficients of-0.273 and-0.254,respectively.It shows that the photosynthetic efficiency of wheat can be improved by improving the stomatal traits of wheat.3.Four wheat stomatal traits were measured under two wheat seasons and two environments using 189 wheat populations as natural populations.Genomewide association analysis of stomatal traits was performed using wheat 660 K SNP chip combined with Blink,CMLM,MLMM and MLM models.445 genetic loci significantly associated with wheat stomatal traits were found.Finally,seven candidate genes directly or indirectly regulating stomatal traits were obtained by annotation.They encode signal recognition particle 54 k Da protein,protein IQ-DOMAIN 1,SOUL heme-binding family protein,26S protease regulatory subunit,G-box binding factor,Aldose 1-epimerase-like and malate dehydrogenase.These candidate genes may regulate wheat stomatal traits by regulating the development of stomatal structure and the metabolism of guard cells.At the same time,five candidate genes regulating stomatal index and one homologous gene related to stomatal density were found.These genes encode O-methyltransferase,chalcone synthase,protein kinase,WD40repeat-like protein,Mitochondrial import inner membrane translocase subunit TIM9 and 60S ribosomal protein L28.In summary,there is a certain correlation between wheat stomatal traits and flag leaf traits,and stomatal traits can be predicted by flag leaf traits.The photosynthetic parameters of extreme materials with stomatal traits were measured,and the law of stomatal traits and photosynthetic capacity was found.The photosynthetic capacity of varieties with larger stomatal area and smaller stomatal density was generally stronger.Through genome-wide association analysis,seven candidate genes that may be directly or indirectly related to stomatal traits were screened,and six candidate genes previously discovered were also found.These results will help to strengthen the in-depth understanding of wheat stomatal traits and provide reference for the screening and innovation of wheat stomatal traits.