Effects Of Inoculating Arbuscular Mycorrhizal Fungi On The Growth Of Alfalfa In Acidic Soils With Different Aluminum Level

Most of the acidic soil is widespread in the south of China with aluminum toxicity,huge losses occurred in arable production.Studying the mechanism of Al toxicity is one of the most effective measures to enhance plant toleranc in acidic soils.Alfalfa（Medicago sativa L.）,an important grass in China,is one of the most sensitive plants to acidic soil environment,and Al has a significant inhibitory effect on the growth of M.sativa.Arbuscular Mycorrhizal fungi（AMF）can improve plant tolerance and reduce the growth suppression.In this study,a pot experiment was conducted to study the effect of AMF on M.sativa（two test materials）growth in different soil Al concentration(Al³⁺Ⅰ:54 mg/Kg;Al³⁺Ⅱ:79 mg/Kg;Al³⁺Ⅲ:104 mg/Kg),using two different Al-tolerant M.sativa cultivars.The main results were as follows:（1）Effect of AMF on agronomic traits and rhizosphere soil properties in Al-contaminated soil:plant height and biomass were significantly decreased in Al-contaminated soil,and root surface area,root length,root volume and root tip number were significantly reduced.The addition of AMF alleviated the negative effect of Al on the growth of two M.sativa species.Inoculation with AMF can significantly increase soil ammonium nitrogen and available phosphorus.Only AMF inoculation significantly increased soil p H in WL440HQ.Soil reactive aluminum content was significantly reduced,37.3%and 36.6%respectively at Al³⁺Ⅱlevel.AMF inoculation reduced the Al content of M.sativa,reduced the toxic effect on M.sativa,and effectively reduced Al transfer to the above-ground.The infection rate of WL525HQ decreased at Al³⁺Ⅲlevel,which was 52.66%.（2）Effect of AMF on physiological factors of M.sativa in Al-contaminated soil:AMF inoculation will significantly increase the enzyme activities of SOD,POD,and CAT in M.sativa,and the content of proline,soluble sugar,soluble protein,and soluble protein will increase;The MDA content of M.sativa WL525HQ and WL440HQ decreased by 30.1%and 28.3%at Al³⁺Ⅱlevel,respectively.AMF can significantly alleviate the harm of Al-contaminated soil.（3）Effects of AMF on organic acid content and the expression of aluminum transporter protein genes of M.sativa in Al-contaminated soil:organic acid content increased with Al addition,with the most significant increase in malic acid,succinic acid and citric acid.The expression of aluminum transporter protein genes Ms MATE1S and Ms ALMT1S were up-regulated with increasing Al concentration,and AMF inoculation significantly promoted organic acid secretion and gene expression.In conclusion,the addition of AMF has positive effect on plant micro-environment,improve the yield,inhibit the transfer of Al to the above-ground parts,enhance the resistance of adversity circumstances with physiological effects and the expression of Al transporter protein genes,and alleviate the inhibitory effect of Al on the growth of M.sativa in acidic soil.