Study On Evaluation Of Stress Resistance Of Three New Replanting-tolerant Apple Rootstocks

Rootstocks play a regulatory role in the growth and fruit bearing of fruit trees.Rootstocks with good resistance to continuous cropping are the key factors affecting the development of apple industry.‘Yanzhen series’ rootstocks are replanting-tolerance rootstocks selected by Yantai Academy of Agricultural Sciences newly,and the evaluation of the resistance of these rootstocks is a necessary condition for large-scale promotion.In this study,three new apple rootstock varieties with resistance to continuous cropping such as ‘Yanzhen No.2’,‘Yanzhen No.5’,‘Yanzhen No.6’ and other seedlings and the tissue culture seedlings with same variety of them,were used as materials to identify their drought resistance,salt resistance and cold resistance.The effects of stress on the external morphology,cell membrane permeability,antioxidant enzyme activity,osmoregulation substance and Photosynthesis of different apple rootstocks were studied,so as to obtain the resistance characteristics of three kinds of rootstocks,and provide reference for the experiment promotion and production guidance.Meanwhile,a comparative study was conducted on the consistency of the resistance performance between the seedling and the tissue culture seedling of the same variety,so as to provide a theoretical basis for the establishment of an effective evaluation technology system for resistance identification in vitro and seedling stage of apple rootstocks,and a certain reference for further understanding of resistance mechanism and physiological adaptation mechanism of apple.The results are as follows:(1)The drought resistance of the seedlings for each tested rootstock from strong to weak was as follows: ‘M.sieversii(Ledeb)Roem’,‘M9’,‘Yanzhen No.5’,‘M.hupehensis’,‘Yanzhen No.6’ and ‘Yanzhen No.2’;the salt resistance from strong to weak was as follows: ‘Yanzhen No.2’,‘M9’,‘Yanzhen No.6’,‘M.hupehensis’,‘Yanzhen No.5’ and ‘M.sieversii(Ledeb)Roem’;the cold resistance from strong to weak was as follows: ‘Yanzhen No.6’,‘Yanzhen No.5’,‘B9’,‘Yanzhen No.2’,‘M.hupehensis’ and ‘M9’.(2)The drought resistance of tissue culture seedlings for each tested rootstock from strong to weak was as follows: ‘M9’,‘Yanzhen No.5’,‘M.hupehensis’,‘Yanzhen No.6’,‘Yanzhen No.2’ and ‘B9’;the salt resistance from strong to weak was as follows: ‘Yanzhen No.2’,‘M9’,‘Yanzhen No.6’,‘M.hupehensis’,‘Yanzhen No.5’ and ‘B9’;the cold resistance from strong to weak was as follows: ‘Yanzhen No.6’,‘Yanzhen No.5’,‘B9’,‘Yanzhen No.2’,‘M.hupehensis’ and ‘M9’.(3)Comparing the evaluation rankings of drought resistance and salt resistance of 5 apple rootstock seedlings and tissue culture seedlings and cold resistance of 6 apple rootstock seedlings and tissue culture seedlings,the results are consistent.The method of early identification of the resistance of the tissue culture seedlings of this variety can be used to predict the resistance of the seedlings.(4)The resistance of three new apple rootstock varieties to continuous cropping was obtained.The drought resistance grade of ‘Yanzhen No.2’ was low,which could only grow in the soil environment with sufficient water;with the high salt resistance grade,it could adapt to moderate salinized soil(about 0.2% of soil salt content);with a semilethal low temperature of-33.91℃,it could be planted testly in Northeast China where the annual minimum temperature is not lower than-34℃.The drought resistance grade of ‘Yanzhen No.5’ was medium,which could adapt to the medium drought soil;because its salt resistance grade was non-resistant,it was suitable for planting in normal soil below mild salinization(about 0.05% of soil salt content);with a semilethal low temperature of-38.94℃,it could be planted testly in Northeast China and other areas where the annual minimum temperature is not lower than-39℃.The drought resistance of ‘Yanzhen No.6’ is medium,which could adapt to mild and medium drought soil;with the medium salt resistance grade,it could adapt to mild salinized soil(about 0.1% of soil salt content);with a semilethal low temperature of-36.67℃,it could be planted testly in Northeast China and other areas with annual minimum temperature not lower than-37℃.