Evaluation Of Water Use Efficiency Of Different Apple Scion-Rootstook Combinations Under Long-Term Drought

Shaanxi is the main province of apple production,and the cultivation area and yield of apple are among the top.However,there are still the following problems in the development of apple industry in Shaanxi:1.The variety structure is unreasonable,the main varieties are single,and there is a lack of self-cultivation varieties;2.The cultivation system is backward,mainly with dense planting of arborized rootstocks,resulting in low production efficiency and inconvenient mechanized operation;3.The uneven distribution of water resources and insufficient precipitation affect fruit yield and quality.Therefore,studying the effects of different rootstock and panicle combinations on the growth and development of apple plants and the water use efficiency of long-term drought is conducive to exploring diversified rootstock variety combinations and screening combinations with high water use efficiency;It is helpful to reasonably select the combination of rootstock and scion varieties in production,so as to improve the yield,quality and economic benefits of apple,which has important practical significance for the apple industry in China,especially in the loess plateau production areas.In this experiment,the potted seedlings of 9 rootstock and scion combinations grafted with 3 self-rooted rootstocks:M26,M9T337,Sorbus fulva(MP)and 3scion varieties:Fuji(Fn),Honeycrisp(Hy)and Qinguan(Qg)were used as the research objects.The seedlings were treated with moderate drought for 60 days,and the growth and physiological indexes were recorded.Through observing the growth,development and fruit performance of Fuji adult trees grafted on M26 self-rooted rootstock,Malus micromalus rootstock(MS)and M26 intermediate rootstock(M26/MS),the effects of different rootstocks on apple growth and water use efficiency under long-term drought were comprehensively evaluated.The main research results are as follows:1.A long-term moderate drought treatment was conducted on potted seedlings under 9combinations of rootstocks and panicles.Multiple physiological and biochemical indicators during the treatment process,including plant height,stem diameter,photosynthetic rate,transpiration rate,chlorophyll content,relative water content,relative conductivity,antioxidant enzyme activity,dry matter accumulation,and long-term water use efficiency,were measured.The long-term water use efficiency and drought resistance coefficient constructed based on physiological indicators related to drought stress were analyzed through subordinate functions,The water use efficiency and comprehensive drought resistance of different combinations of rootstocks and panicles were sorted and classified.The results showed that there were differences in the growth performance of potted seedlings with different combinations of rootstocks and panicles.Under moderate drought conditions,there were differences in the long-term water use efficiency of the same variety grafted on different rootstocks The variety ‘Qinguan’showed grafting on MP>T337>M26,Both the ’Honey Crisp’ and ‘Fuji’ varieties showed grafting on the fruit of MP>M26>T337.2.Under drought stress,the net growth of plant height,stomatal opening,net photosynthetic rate,transpiration rate,relative water content,and chlorophyll content of potted seedlings decreased to varying degrees,while relative electrical conductivity,leaf thickness,malondialdehyde content,and antioxidant enzyme activity increased to varying degrees.For all the parameter indexes that have changed due to drought,the drought resistance coefficient is used to establish a membership function to comprehensively evaluate the drought resistance ability of different rootstock and panicle combinations.The evaluation results are as follows:the comprehensive drought resistance ability of nine materials is divided into four categories from strong to weak:Class I(Qg/T337,Hy/T337,Fn/MP,Qg/MP),Class II(Qg/M26,Hy/M26,Fn/T337),Class III(Fn/M26),and Class IV(Hy/MP).3.Taking Fuji adult trees grafted with three different rootstocks at the Luochuan Experimental Station as the research object,the growth and development,fruit quality,and yield of different materials were compared.It was found that the fruit trees grafted with M26/MS and MS rootstocks had better tree vigor and fruit quality,which was superior to the trees grafted with M26;In terms of yield,the plants grafted with M26 self rooted rootstocks have the highest yield per mu,followed by the fruit trees grafted with MS rootstocks,and the fruit trees grafted with M26 intermediate rootstocks have the lowest yield.