Effects Of Drought Stress On Wheat Growth And Identification Methods Of Drought Resistance Of Varieties

Seasonal drought occurs frequently in the main wheat producing areas in northern China.Identifying and screening wheat varieties that take into account drought tolerance and yield stability is the most effective way to deal with global climate change and water shortages.In this paper,the simulated dry shed facilities under artificial drought stress were used to set up drought treatment and normal irrigation treatment,and different genotypes of wheat varieties that were popularized and applied in production were selected to systematically measure the response changes of plant morphophysiological indicators under different water conditions.The correlation degree-membership function algorithm is used to construct the estimation model of yield drought resistance index,and screen out the suitable drought resistance identification index.At the same time,a thermal infrared imager was used to obtain wheat canopy temperature images,and methods such as temperature frequency histograms were used to extract canopy temperature characteristic parameters,and to clarify the relationship between them and yield drought resistance index,in order to provide technology for rapid and non-destructive screening of drought-resistant crop varieties.support.The results of the study are as follows:(1)Under drought stress,the plant height,water content,leaf area index,chlorophyll content and chlorophyll fluorescence parameters and other indicators of wheat showed a decreasing trend in different degrees compared with the irrigation treatment groups,and the decrease rate was different due to the different levels of wheat drought resistance.It is shown that with the improvement of the drought resistance level of wheat,the decline range will gradually decrease,and the specific decline range of various varieties is extremely weak drought resistance varieties > weak drought resistance varieties > medium drought resistance varieties > strong drought resistance varieties.However,water stress significantly increased the content of wheat osmotic adjustment substances(proline,free amino acids,total soluble sugar),and the increase rate would increase with the increase of the drought resistance level of wheat.Specifically,the extremely weak drought resistance varieties < weak Drought-resistant varieties < medium drought-resistant varieties < strong drought-resistant varieties.(2)The variation range of each trait under drought stress was relatively large at booting stage and filling stage(7.4%-41.7%),while the variation range at jointing and flowering stage was relatively small(9.63%-31.63%).There is a significant correlation between the indicators in each period.Further,principal component analysis was used to convert the traits of jointing stage,booting stage and flowering stage into 6,and the grain filling stage into 5 independent comprehensive indicators,and the cumulative contribution rate reached 89.03%,88.69%,87.68% and 85.83% for above four stage.The membership function method was introduced to calculate the comprehensive drought resistance evaluation value(SD value)for each growth stage,and the quantitative relationship between SD value and yield drought resistance index(DRI)was analyzed,and the fitting precision of the simulation equation were the highest 0.744 at anthesis and the lowest 0.679 at filling.In order to better integrate the information of drought resistance at different stages,the first four parameters with the highest correlation with SD value at each stage were selected through the grey correlation degree and combined to form an evaluation index system for the whole growth period.The principal component and membership function analysis were carried out again to calculate the comprehensive evaluation value of drought resistance based on whole growth stages(MD),and this derived MD value can explain 87.8% of the DRI variation,which represented a 18.1% increase over determinative coefficient of the best single stage.According to the MD value,the varieties can be divided into four categories,moderate drought resistance,moderately weak drought resistance,weak drought resistance and extremely weak drought resistance.and the plant height and leaf water content at jointing,proline,plant height and chlorophyll a at booting,chlorophyll a and soluble sugar at anthesis,and proline and leaf water content at filling were selected as a set of screening indicators.(3)The canopy thermal infrared images of different drought-resistant cultivars under drought stress are significantly different,extracted canopy temperature characteristic parameters by using temperature frequency histogram and other analysis methods,clarified the quantitative relationship between temperature characteristic parameters and drought resistance index,and analyzed the effectiveness of canopy temperature characteristic parameters on screening drought-resistant varieties of winter wheat.The grading criteria based on the yield drought resistance index(DRI)classified the measured wheat varieties into four drought resistance categories,Extracting characteristic parameters of canopy temperature based on thermal infrared images,the stronger the drought resistance of wheat,the smaller variability in canopy temperature and the less dispersion in canopy temperature.The yield drought resistance index(DRI)showed highly significant positive correlation with the deviation between crop canopy temperature and ambient temperature(CTD)at the jointing,booting and flowering stages with the highest correlation coefficient(r=0.79-0.84),while the standard deviation of canopy temperature(CTSD),coefficient of variation(CTCV),water stress index(CWSI)and relative canopy temperature difference(CRTD)were significantly negatively correlated(r=-0.56--0.78).The regression model of yield drought tolerance index(DRI)was built based on canopy temperature characteristic parameters of a single growth period,and the estimation accuracy was r2=0.73-0.87,with the highest accuracy of the prediction model at the jointing stage.And the prediction model of yield drought resistance index(DRI)was constructed based on the combination of relevant canopy temperature parameters CTD,CTCV,and CTSD CWSI of three growth periods,and the accuracy of prediction was significantly higher(r2=0.95)than that based on a single growth period.This research is of great significance for screening drought-resistant and water-saving varieties by means of thermal infrared images,exploit the droughtresistant genetic potential of crops,and promote efficient and water-saving crop production.