Research Upon Salinity Tolerance Improvement Conferred By Piriformospora Indica In Maize(Zea Mays) Seedlings

Maize is one of the major food crops in China.Because of the lack of water resources,the arable land are often accompanied by problems such as drought and salinization.Therefore,improving the resistance of maize to salt damage is the key to solve this problem.Previous study found that Piriformospora indica has the advantages of being able to colonize with many different kinds of plants and increase the growth of host plants,and at the same time it can help host to resist to various abiotic stresses including salt stress.Therefore,there is great theoretical and practical significance to study the mechanism of P.indica regulate maize growth under salt stress.This work was aimed to reveal mechanisms enhancing salinity tolerance in maize roots colonised by P.indica.After colonized with P.indica the maize seedlings were treated by using 100 and 200 mM NaCl in hydroponics for 5 days.The biomass,photosynthesis,antioxidant enzymes of the inoculated and non-inoculated plants were examined.Potassium(K)and sodium(Na)contents of shoot and root,ion fluxes of root,DNA methylation changes of leaves and roots,and leaf gene relative expression were measured.A comprehensive comparison of the differences between the inoculated and non-inoculated plants under salt stress have been done.Results showed that after under 200 mM salt stress 5 days,compared with non-inoculated plants,inoculated plants have 6.89%,11.02%,10.02%,and 12.74%higher in shoot fresh weight,shoot dry weight,root fresh weight and root dry weight;18.26%,7.42%and 34.56%higher in stomatal conductance,total leaf area and net photosynthesis rate;27.42%and 3.65%higher in SOD and POD;24.07%and 50%lower in MDA content in leaf and K~+efflux in root;13.71%higher in shoot K content and 16575%higher in HAK10 expression;the changes of DNA methylation in leaf and root are 6.3%and 25%in 100 mM NaCl condition,under 200 mM treatment are 33%and 50%.In summary,under the salt stress,the P.indica inoculated plants showed higher biomass,photosynthetic capacity,and antioxidant capacity.Through the analysis of the above results,we have following conclusions:under salinity stress,P.indica can regulate the transport of K~+from root to shoot by xylem,specifically,to the photosynthetic zone which can result in higher stomatal conductance and higher photosynthetic capacity;And active stronger antioxidant enzyme(SOD,POD)activity to relieve the ROS toxicity caused by salt stress which can also reduce the level of membrane lipid peroxidation and alleviate the damage to plant photosynthesis ability.Based on above,P.indica can enhance salinity tolerance of maize seedlings.