Evaluation Of Drought Resistance Of Almond Rootstock Resources At Seedling Stage Based On Physiological And Morphological Structure Characteristics

At present,the xinjiang local peach used as the common rootstock for the almond production in Kashgar,which is the main almond planting area in Xinjiang.This rootstock has some problems,including shallow root systems,low resistance to stress(cold and drought),short lifespan,and overgrowth at the graft union at later stages(25～30years after grafting),which severely affects the sustainable development of almond industry in Xinjiang.In this study,the annual seedlings of six Almond Rootstock resources in Xinjiang(Stone almond,Big almond,Bitter almond,Bitter peach×almond,Sweet peach×almond and Local peach)were used as target materials.The physiological and biochemical responses of different rootstock seedlings under progressive drought stress(withholding water for 18 days)and the changes of morphological and structural characteristics of roots,stems and leaves of rootstock seedlings under moderate long-term drought stress(60 days,with moderate drought stress to keep soil RWC 28%～32%)were studied.The drought resistance of 6 rootstock resources was thoroughly estimated by principal component analysis and membership function method.The almond rootstock resources with strong drought resistance were filtered out to supply a theoretical basis to the development and utilization of excellent drought resistant almond rootstock resources in Xinjiang.The research results are as follows:(1)Under the progressive drought stress condition,the leaf RWC of 6 rootstocks continued to decline,among which the decline of Local peach was the most obvious,and it had dropped to the lowest level at 15days;The activities of POD and SOD rised first and then reduced,the rising trend of Bitter almond was the most apparent;On the 18 th day of stress,the MDA content of Stone almond and Bitter peach ×almond was evidently lower than that of other resources(P<0.05).The drought resistance of 6 almond rootstock resources at seedling stage was comprehensively evaluated by membership function method.The order of drought resistance of rootstock was as follows: Stone almond>Big almond>Bitter almond>Bitter peach×almond>Sweet peach ×almond>Local peach.(2)Under long-term moderate drought stress,leaf thickness,upper epidermal cell thickness,mesophyll cell porosity and specific leaf area(SLA)decreased significantly(P<0.05).The morphological structure indexes of stems and leaves showed that there was no evident difference in stem anatomical structure between different rootstocks(P>0.05).The drought resistance of 6 rootstock resources was evaluated from the perspective of leaf anatomical structure.The evaluation results showed that the order of drought resistance from strong to susceptible was: Bitter almond>Big almond>Sweet peach×almond >Stone almond>Bitter peach×almond>Local peach.(3)It was found that the thickness and number of cork layers of stone almond were the largest,which was prominently higher than that of the other 5 rootstock resources(P<0.05);After temperate drought stress,the cork layer of almond resources was thickened(P>0.05).The evaluation results showed that: Big almond>Stone almond>Bitter almond>Sweet peach×almond>Bitter peach×almond >Local peach.(4)The results showed that under 60 days of moderate drought stress,only the total root length、surface area and volume of bitter almond increased prominently,and the root growth of Bitter almond was prominently higher than that of other rootstock resources(P<0.05);The proportion of fine root biomass of almond resources(Stone almond,Big almond and Bitter almond)greater than 0.5 mm is higher,among which Stone almond is the highest(80%),indicating that almond resources have stronger drought tolerance than other rootstock resources.(5)Through two different drought stress treatments,the response of leaf physiology and biochemistry and the morphological structure of roots,stems and leaves to drought stress was studied.The drought resistance of 6 rootstock resources at seedling stage was evaluated by principal component and membership function methods.The evaluation results showed that the drought resistance of almond resources(Stone almond,Big almond and Bitter almond)was stronger than that of peach×almond,while local peach was more sensitive to drought than other rootstocks.