The Screening Of Saline-alkaline Tolerance In Apple Rootstocks

In this experiment,7 kinds of four-year-old apple rootstocks were used as test materials.NaCl,Na₂SO₄,NaHCO₃ and Na₂CO₃ were added to the nutrient solution and mixed in the ratio of 1:9:9:1.In order to study the effects of salt-alkali complex stress on the physiological,photosynthetic characteristics and leaf microstructure of apple rootstocks,simulated salt-alkali complex stress at concentrations of 0（1/2Hoagland）,15,30,45,60 mmol/L,on the basis of which a comprehensive evaluation and mechanism of salinity tolerance of apple rootstocks was carried out.Finally,the effect of field salinity on the growth of different apple rootstocks was investigated in combination with the validation of field trials to select rootstocks suitable for practical production.The results of the study are as follows:（1）With the intensification of stress intensity,the chlorophyll content of the leaves of each rootstock continued to decrease;the relative conductivity,MDA and proline content all showed an overall increasing trend;the SOD and CAT activities and the total soluble sugar content all increase first and then decrease;while the POD activity and soluble protein content had two changing trends:"first rise and then fall"and"increase-decrease-increase".The salt-alkali resistance of apple rootstock was evaluated by membership function method.The results showed that the order of the strength and weakness of the salt-alkali resistance of the rootstocks was as follows:M.robusta>M.hupehensis>M.xiaojinensis>M.sieversii>M.chaenomeles>M.baccata>M.hupehensis（Pamp.）.（2）Photosynthetic parameters of different apple rootstocks under different stress concentrations showed that M.hupehensis（Pamp.）and M.chaenomeles were strongly damaged by salt-alkali complex stress,and Pn,Gs,Ci and Tr of leaves showed a general downward trend with the increase of salt concentration and p H,among which the photosynthetic parameters of M.hupehensis（Pamp.）rootstocks showed the largest decrease.The photosynthetic parameters of the other rootstocks increased first and then decreased.Among them,the Pn and Gs of the leaves of M.robusta,M.hupehensis and M.xiaojinensis decreased less after the stress,which reflected the better adaptability to the stress environment.（3）An optical microscope was used to observe 14 leaf anatomical structures of 7 apple rootstocks before and after salt-alkali complex stress,and principal component analysis and cluster analysis were used to comprehensively evaluate the observation indicators.It is concluded that the salt-alkali resistance of the rootstocks in order from strong to weak is M.robusta、M.xiaojinensis、M.hupehensis、M.sieversii、M.chaenomeles、M.baccata、M.hupehensis（Pamp.）.The salt-alkali resistance of the rootstocks is divided into three categories,of which M.robusta with the strongest salt-alkali resistance is a separate category;M.xiaojinensis and M.hupehensis with strong salt-alkali resistance are one category;white M.sieversii,M.chaenomeles,M.baccata and M.hupehensis（Pamp.）with weak salt-alkali resistance are classified into one category.（4）Through field observation of different apple rootstocks,research on the growth and development of rootstocks,and determination of chlorophyll content,specific leaf weight,and leaf iron content.The results showed that M.xiaojinensis and M.robusta grew well in the saline alkali soil with strong photosynthetic capacity,high content of active iron and low content of total iron in leaves.Although M.chaenomeles,M.sieversii and M.hupehensis（Pamp.）grow normally,the leaves are accompanied by slight yellowing symptoms.The new shoots of M.baccata show obvious symptoms of iron deficiency and chlorosis,the photosynthesis performance is the worst,the active iron content of the leaves is the smallest and the total iron content is the largest.After comprehensive analysis,it is believed that M.xiaojinensis and M.robusta have strong salt-alkali resistance,M.baccata has the weakest salt-alkali resistance,and M.sieversii,M.hupehensis（Pamp.）and M.chaenomeles have the salt-alkali resistance between the above ones.（5）Comprehensive evaluation of the salt-alkali resistance of different apple rootstocks from physiological,photosynthetic characteristics and leaf microstructure,combined with full verification in field experiments.After comprehensive analysis,it is concluded that the apple producing area of southern Xinjiang is the most suitable for the production of M.robusta.