Relationship Of Canopy Temperature, Stable Carbon Isotope Ratios In Flag Leaves And Water Soluble Carbohydrate In Stem With Water Use Efficiency In Various Genotypes Of Winter Wheat

Facing the shortage of water resources and increased drought, it is necessary to carry out water-saving agriculture, and improving the water use efficiency(WUE) of crops is the key and potentiality to efficient water use. Seeking some indicators for selecting high water use efficiency varieties is the important part of the water-saving agriculture research. Domestic and foreign scientists had studied this problem from morphological characters, physiological indexes to molecular biology. Lots of research showed that canopy temperature(CT), stable carbon isotope(δ13C) and water soluble carbohydrate(WSC) have close relationship with crop yield and water use efficiency. But the research about analyzing the differences of CT,δ13C, WSC and the correlation between CT,δ13C, WSC with water use efficiency in various genotypes of winter wheat is few. The present study was carried out with fifteen winter wheat genotypes (twelve from North China and three from Texas America) in Loess Plateau of East Gansu under dryland and supplemental irrigation condition at jointing stage to analyze the differences of CT,δ13C and WSC in various genotypes, and search the correlation between them with grain and WUE. It will be helpful to seek the indicator for selecting high water use efficiency varieties. The results of study are:1. Different genotypes had considerable differences in grain yield and WUE(P<0.001) whether under dryland or supplementary irrigation condition. The average yeild is 2393.1kg·hm-2 and 4182.4 kg·hm-2 under two conditions respectively. Difference between the maximum yield and minimum yield is 1110.4 kg·hm-2 and 1609.7 kg·hm-2 under dryland and supplementary irrigation condition, respectively. And the coefficient of variation of yield is 12.24%,9.13% under two differert conditions respectively. Difference between the maximum yield and minimum WUE is 4.64 kg·hm-2·mm-1 and 4 kg·hm-2·mm-1 under two differert conditions. The coefficient of variation of WUE is 13.75%,8.73% respectively. But the water consumption in various genotypes is not significantly. The most yield under supplementary irrigation condition is higher than it under dryland condition. With irrigation of 100mm water at jointing stage, various genotypes of winter wheat had significant compensation or super compensation effects.2. The difference of canopy temperature(CT) among various genotypes wheat is apparent (P<0.001) during grain filling stage except late grain filling stage whether under dryland or supplementary irrigation condition. And the CT value under dryland condition is higher than it under irrigation condition. The CT values are different among the determine days, and the difference is significantly. But these changes has not influenced the considerable differences of CT among various genotypes. It has highly negative correlations of CT value related to grain yield and WUE excepted June 10 whether under dryland or irrigation condition.3. It showed that different genotypes had considerable differences in stable carbon isotope(δ13C) in May 6(eary filling stage), May 16(middle filling stage), May 31 (mid-late filling stage) and June 10(late filling stage) (P<0.001). Theδ13C values among determine days is not significantly. The reasults indicated that the relationship betweenδ13C value with grain yield and WUE is highly positive whether under dryland or irrigation condition in four above determine stage.4. The water soluble carbohydrate(WSC) among various genotypes is different in grain filling stage(P<0.001). The WSC increased with grain filling proceeding, reached the maximun at mid-late filling stage, and then declined whetherr under dryland or irrigation condition. The WSC value under dryland condition is higher than it under irrigation condition no matter in which determine stage. The result showed that the correlation of WSC value related to grain yield and WUE is not significantly at early and middle filling stage(R2=0.0555～0.1381), while positive at mid-late and late filling stage(R2=0.2527～0.3484) under dryland condition. And highly positive correlations of WSC related to grain yield and WUE were obtained (R2=0.3427～0.4951) under supplementary irrigation condition, especially after mid-late grain filling stage.5. The multiple regression of WUE to canopy temperature(CT), stable carbon isotope(δ13C) and water soluble carbohydrate(WSC) showed that the canopy temperature(CT) is more reliable than stable carbon isotope(δ13C) and water soluble carbohydrate(WSC) in evaluating WUE. And it can be considered a good indicator to select high water use efficiency varieties in field.