Analysis On The Drought Resistance Of Wheat Cultivars In Seedling Stage In Southwest Area And Transcriptome Analysis Of Wheat Root In Drought Stress By Ethrel Soakin Treatment

Southwest wheat area is the third barley area in China,wheat is mainly distributed in hilly land.The hilly land always is drought and barren.Due to the poor irrigation conditions in the hilly area and lacking rain in winter and spring,the weak seedlings have greatly limited the yield of wheat in the region.Therefore,it is urgent to select the high drought-resistance wheat varieties at seedling stage to ensure the high and stable yield.Evaluating the drought resistance 42 wheat cultivars seedlings in the southwest of China.Natural drought stress was performed by pot culture and field cultivation.Then 10 traits of wheat cultivars cultured in pot and 6 indicators of wheat cultivars cultivated in field in harvest time were measured.Comprehensive assessment on drought resistance and classification of these wheat cultivars were implemented by using weighted membership function,clustering analysis and stepwise regression based on every single index of drought resistance coefficient.The seed soaking of ethephon can improve the drought resistance of wheat seedling.In order to clarify the mechanism,under drought conditions the morphological and physiological characters were compared between different soaking treatments.The results are showed as follow:1.42 wheat cultivars were divided into four drought-tolerant types by cluser analysis,3 of the 42 varieties were drought-sensitive type,23 varieties were weak drought-resistance type,13 were medium drought-resistance type,and 3 were high drought-resistance type.A mathematical evaluation model for wheat drought tolerance was established that containing 16 drought resistance coefficients of seeding stage and harvest period by means of regression analys is,andD1=-1.593+0.152X1+0.293X2+0.256X3+0.151X5+0.426X6+0.107XT+0.958X12+0.085X14+0.056X15+0.205X16(r=0.9994).Average fitting accuracy of all varieties were 99.23%.A mathematical evaluation model for wheat drought tolerance was estab-lished that containing 10 drought resistance coefficients of seeding stage by means of regression analysis,andD2=-0.677+0.218X1+0.481X3-0.803X4+0.230X5+1.232X6(r=0.821).Average fitting accuracy of all varieties were 88.50%.Thed rought resistance in wheat seedling stage significantly associated with the indexes in harvest period.It is more dependable to evaluate the drought resistance uniting the seeding and yield trait.But determination of the five indicators(leaf area,root length,shoot dry weight,root dry weight,the whole plant dry matter accumulation)in seedling stage can be used for rapid identific ation and prediction of other wheat varieties.2.Under drought stress,the dry matter accumulation of wheat was inhibited.As the limitation of shoot more than the root,the root shoot ratio is increased in drought stress.The water content is reduced,but the root activity,antioxidiant enzyme activity and osmoregulation substance content are increased in drought stress.The increasing of malonaldehyde indicates that wheat leaf membrane is damaged by peroxidation.The root activity,SOD activity and proline content of Ethephon soaking treatment are more than water soaking treatment.So it is possible that Ethephon soaking treatment keep more water content and dry matter accumulation in drought stress.3.Comparison on transcriptome between wheat root grown under drought and control 3197 and 2586 differentially expressed genes in Ethephon soaking treatment and water soaking treatment are found at 1 hour after drought stress.4487 and 4983 differentially expressed genes in Ethephon soaking treatment and water soaking treatment are found at 12 hour after drought stress.Gene ontology analyses showed that differentially expression genes enrich in response to growth hormone,oxidation-reduction process and cinnamic acid biosynthetic process in water soaking treatment after 1 hour drought stress.Differentially expression genes enrich in response to growth hormone,oxidation-reduction process and protein phosphorylation in Ethephon soaking treatment after 1 hour drought stress.Differentially expression genes enrich in cinnamic acid biosynthetic process,oxidation-reduction process and nicotianamine biosynthetic process in water soaking treatment after 12 hour drought stress.Differentially expression genes enrich in cinnamic acid biosynthetic process,L-phenylalanine catabolic process and oxidation-reduction process in Ethephon soaking treatment after 12 hour drought stress.On the whole,the up-regulated expression of hydrogen peroxide catabolic process,response to abscisic acid and defense response genes maybe the mechanism of the Ethephon soaking treatment improve drought resistance.