Preliminary Study On Improving The Salt Tolerance Of Phyllostachys Edulis By Piriformospora Indica And Its Mechanisms

Phyllostachys edulis is an important bamboo species for both shoot and timber production in China because of its rapid growth,short growing cycle,easy afforestation,great ecological and social benefits.Ph.edulis has special soil requirement,preferring to acidic sandy soil with fertility,moisture,as well as good drainage and air permeability.However,the area of saline soil in China is so large,about 3.46million hectares,that improving the salt-alkali tolerance of Ph.edulis is of great significance for developing the rational utilization of Ph.edulis in salt-soaked land and protecting the ecological environment in China.Piriformospora indica is an endophytic fungus in plant roots.It has been treated as biological agent for various plant species to promote plant growth and improve their tolerance to biotic and abiotic stresses.In this paper,the effects of Pi.indica on the growth and salt tolerance of Ph.edulis were studied,and the molecular mechanism of Pi.indica improving salt tolerance of Ph.edulis was preliminarily explored.The main results are as follows:(1)The clots and suspensions of Pi.indica were made to treat with Ph.edulis plantlets and seedlings.The results showed that the colonization time of tissue culture seedlings was short,but with un-uniformed growth process after domestication;the seedlings grown in soil matrix had the same growth trend,but it needed a longer colonization time.Finally,the Ph.edulis seedlings grown in wet filter paper can be colonized successfully by Pi.indica after 10 days’treatment.The seedlings can grow normally after two weeks’transplantation with consistent growth process.(2)Under normal growth conditions,the colonization of Pi.indica could promote the growth of Ph.edulis and increase its biomass.Different NaCl concentrations(0 mM,100 mM,150 mM,200 mM)were used to treat Ph.edulis seedlings which colonized by Pi.indica(Treatment)and uncolonized seedlings set as control(CK).The variation trend of Photosynthetic System II(PSII)Primary Light Energy Conversion Efficiency(Fv/Fm)in leaves of Ph.edulis in response to stress time were analyzed.The results recovered that the variation trend of Fv/Fm between Treatment and CK was the most significant.Therefore,150 mM NaCl concentration was applied to Ph.edulis seedlings treatment.The results showed that the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)in the leaves of Ph.edulis which colonized by Pi.indica were significantly higher than those of non-colonized plants,while the content of MDA was significantly lower than that of non-colonized ones,indicating that Pi.indica may decrease the damage of salt stress to Ph.edulis by increasing the activity of antioxidant enzymes and decreasing the content of MDA.(3)The expressions of 7 salt tolerance related genes in leaves of Ph.edulis was measured under150 mM NaCl treatment.The expressions of PheSOS1 and PheSOS3,membrane-bound transporters PheVHA-B1,PheVHA-B2 and K~+channel protein PheKAT1 in Pi.indica colonized bamboo leaves were higher than that in CK.It suggested that Pi.indica may improve salt tolerance of Ph.edulis by affecting the expression of salt tolerance related genes and maintaining the ion homeostasis of cells.