Screening For Drought-resistant Wheat Varieties In North Central Hebei Province And Their Physiobiochemical Responses To Drought Stress

Drought and water shortage is one of the main stress factors limiting wheat production in Hebei Province,including the middle and north of Hebei Province.Therefore,the objectives of present study are to screen drought-resistant or water-saving wheat varieties suitable for the regional conditions in the middle and north of Hebei province,to understand the physiological basis for drought resistance,and to find out the indicators for wheat drought resistance using a set of twelve wheat varieties under simulated water stress and re-watering conditions.Length,fresh weight,total volume,activity,total and active absorption area of root were used as indicators to calculate drought resistance comprehensive evaluation value(D-value),comprehensive drought-resistance coefficient(CDC-value),weighed drought-resistance coefficient(WDC-value),frequency analysis,principal component analysis PCA),grey relational analysis,clustering analysis,subordinate function analysis,and stepwise regression analysis.Nine physio-chemical traits in addition to the nine agronomic traits of twelve wheat varieties under rain-fed conditions were used to investigate drought-resistance difference among wheat varieties at different growth stages(i.e.jointing,booting,flowering and grain-filling stages).In addition,twenty-five wheat varieties registered in Hebei Provincewere subjected to different water treatments(D2,D1 and D0)to evaluate their drought resistance in Xushui county during 2019/2020 cropping season.The main results are as follows:1.Using 20%PEG6000 to simulate drought stress at seedling stage,twelve wheat varieties were tested to infer the relationship between root traits and drought resistance.Frequency analysis showed that the sensitivity degrees of each root trait to PEG stress was followed as root length,root activity,total root absorption area,active root absorption area,root fresh weight and root volume.Root dry weight was sensitive on the fifth day of PEG stress,but not after re-watering.PC A analysis showed that 93.11%and 90.51%of the original data information of wheat drought resistance could be represented by two principal components on the fifth or third day of PEG stress,respectively.Under PEG stress and after re-watering,drought sensitivity evaluation results of different varieties based on CDC value,WDC value and D value were similar.Grey correlation analysis showed that the correlation degree between DC value and D value was the same as that between WDC value and DC value on the fifth day of PEG stress,and the order was active root absorption area,total root absorption area,root activity,root dry weight,root volume,root length and root fresh weight,accordingly.On the third day of rehydration,the correlation degree of DC value,WDC value and D value was similar.Based on the D value,drought resistance of these wheat varieties were divided into three classes,and the results were the same on the fifth day of PEG stress and the third day of rehydration:the first group was resistant varieties,including Shimai 22,Xiaoyan 60,Shinong 952,Zhongmai 1062,Zhongxinmai 99 and Xitu555;the second was medium resistant varieties,including Zhongxinmai 9,Zhongmai 155 and Henong 6425;the remaining three varieties,Cangmai 119,and,fell in the third class(sensitive varieties).Except for the fresh weight,dry weight and root activity,the subordinate function value,D value,CDC value and WDC value of other indexes increased with the increase of drought resistance level.Stepwise regression analysis showed that,the five indexes of total root absorption area except root length and fresh weight on the fifth day of PEG stress were closely related to D value;on the third day of rehydration,root length,root activity and active root absorption area were closely related to D value.2.The results showed that,compared to normal irrigation(field),grain numbers per spike of twelve wheat varieties increased significantly under field drought stress,while the other agronomic traits decreased with different degrees.The largest reduction was in tiller number and yield,and the smallest was in spikelet number.Under drought stress,number of sterile spikelets of Henong 6425,Zhongxinmai 9,Heng 4399,Cangmai 119 and Lunxuan 169 increased,while the number of sterile spikelets of remaining seven varieties decreased.Decreasing range of each character and the increase of grain number per spike of Shinong 952,Shimai 22,Zhongxinmai 99,Xitu 555,Xiaoyan 60,Zhongmai 1062 and Zhongmai 155 were smaller,but the opposite was for Heng 4399,Cangmai 119 and Lunxuan 169.Under the condition of dry shed,the changes of agronomic characters of varieties such as Shinong 952,Lunxuan 169,Zhongxin mai 99,Xitu 555,Heng 4399 and Xiaoyan 60 were small under drought stress.3.Under stress and control conditions(field),RWL and RWC tended to increase first and then decrease in each growth stage,and the decrease amplitude was the smallest at filling stage and booting stage,respectively.During jointing stage,the decrease of RWL and RWC of Shinong 952,Shimai 22,Xiaoyan 60,Xitu 555 and Zhongxin 99 was lower than that of Henong 6425,Cangmai 119 and Heng4399.The F0 value of D0 treatment was higher than that of D2,while the chlorophyll content,Fm value and Fv/Fm value of D0 treatment were lower than those of D2.The results showed that the decrease and increase range of chlorophyll content and Fm value were different under drought stress.Varieties with the smallest decrease in chlorophyll content and Fm value were Shinong 952 and Shimai 22,varieties with the smallest decrease in Fv/Fm were Shinong 952 and Xitu 555,and varieties with the smallest increase in F0 were Shinong 952 and Xiaoyan 60.Under the condition of dry shed,the RWL,RWC,chlorophyll content and chlorophyll fluorescence parameters of heng4399,Xitu 555,Lunxuan 169,Zhongmai 1062 and Xiaoyan 60 decreased or increased less than Cangmai 119 and Zhongmai 155.4.Activities of SOD,cat and MDA in flag leaves of twelve wheat varieties at different growth stages were measured.The results showed that except for SOD at jointing stage,activities of SOD,cat and MDA content increased under drought stress in other stages.The increasing range of SOD was different at different growth stages.The increase of SOD was the largest at filling stage,CAT and MDA were the largest at jointing stage,and the smallest at filling and flowering stages.The increase range of different drought resistant wheat varieties was also different,in which the smallest increase of SOD activity was found in Shinong 952 and Zhongxinmai 99,the largest in Heng 4399 and Zhongxinmai 9;the smallest increase in CAT activity and MDA content was in Shinong 952 and Shimai 22,and the largest increase was in Cangmai 119 and Heng 4399.5.Shinong 952,Zhongxinmai 99,Shimai 22,Xitu555,Xiaoyan 60 and Zhongmai 1062 showed good drought resistance at seedling stage(PEG simulated drought)and field(Teaching and experimental base of Hebei Agricultural University),Heng4399 and Lunxuan 169 showed better drought resistance under dry shed condition.Root length,root activity,total root absorption area and root active absorption area can be used as drought resistance evaluation indexes of wheat varieties at seedling stage.Ten agronomic and nine physiolo-chemical traits at different growth stages of twelve wheat varieties with different drought resistance were analyzed using principal component analysis.Three principal components for wheat drought resistance were obtained,including Fv/Fm at jointing,booting and grouting stages,relative water content at flowering stage,and tillering number at mature stage.6.Combined with yield under D0 treatment and drought resistance index,seven wheat varieties were regarded as varieties with better drought resistance,while wheat variety,Kemao 53,was regarded as variety with better water-saving ability.