Influence Of Arbuscular Mycorrhizal Fungi (AMF) Inoculation On Salt Tolerence Of Populus Cathayana Females And Males

Using Illumina Miseq,we tested microbial structures in the rhizosphere of Populus cathayana at Chaka Salt Lake.The effects of arbuscular mycorrhizal fungi inoculation on microbial community in the rhizosphere of P.cathayana,water status,photosynthesis,osmotic adjustment,antioxidant capacity,nutrient elements and relative expressions of PcSOS genes were tested.From above,the potential role of AMF in improving salt tolerance were discussed.Main results are showed as followings:1.Microbial community in the rhizosphere of P.cathayana females and males along a salinity gradient at Chaka Salt LakeWith increasing of salinization,microbial community diversity in the rhizosphere of P.cathayana increased first and then decreased,especially for fungal community.Among 5 phyla of fungi and 925 different OTUs,52 OTUs were specific for males,69 were specific for females and 804 were common for both genders.Among 18 phyla of bacteria and 6544 different OTUs,990 OTUs were specific for males,571 were specific for females and 4983 were common for both genders.Redundancy analysis（RDA）showed that available K,ammonium nitrogen（NH₄-N）,nitrate nitrogen（NO₃-N）,Na⁺,Cl^-contents and EC were the main factors affecting microbial community in the rhizosphere of P.cathayana.2.Impact of salt stress and arbuscular mycorrhizal fungi on microbial community in the rhizosphere of P.cathayanaSalt stress reduced microbial community diversity in the rhizosphere of P.cathayana.Under salt stress,exogenous AMF（R.irregularis）inoculation increased fungal diversity in the rhizosphere of females and males,including increased Shannon-Wiener index H′（23.07%and11.71%）,Evenness E_h（6.17%and 1.15%）,Richness S（29.19%and 35.76%）and decreased Simpson index D（38.89%and 35.40%）.Cluster analysis showed that target microbial community similarity in the rhizosphere of males under salt stress were higher;AMF inoculation had a significantly effect on target microbial community in the rhizosphere of females;AMF inoculation had greater effects on target microbial community in the rhizosphere of females than males.3.Influence of arbuscular mycorrhizal fungi on photosynthesis and water status of P.cathayana females and males under salt stressSalt stress damaged root system and leaf surface structure,increased water use efficiency,reduced relative water content,decreased photosynthesis and chlorophyll fluorescence parameters and slowed down growth rates of P.cathayana.Under salt stress,compared to non-inoculation treatments,AMF inoculation could increase RL（23.51%and 28.62%）and RSA（12.06%and 9.03%）,reduce stomatal density,expand guard cells area,increase Pn（0.92%and12.51%）and qN（6.75%and 15.19%）,enhance photosynthetic efficiency and promote growth of female and male cuttings.The study clearly elucidated beneficial effects of AMF on photosynthesis and water status of P.cathayana under salt stress,especially in male cuttings.4.Influence of arbuscular mycorrhizal fungi on osmotic adjustment and antioxidant capacity of P.cathayana females and males under salt stressSalt stress significantly inhibited accumulations of biomass,glycine betaine,soluble sugar,soluble protein,malondialdehyde and activated antioxidant systems.Under salt stress,compared to non-inoculation treatments,AMF inoculation increased proline（18.91%and26.77%）and glycine betaine（4.82%and 18.52%）contents,reduced MDA（13.38%and31.69%）,H₂O₂（6.22%and 10.28%）and O₂^·-（7.97%and 9.63%）contents,improved POD（4.38%and 40.87%）and CAT（13.13%and 12.91%）activity in female and male roots.The study clearly elucidated greater effects of AMF on osmotic adjustment and antioxidant capacity in male cuttings,mainly in underground systems.5.Sex-specific nutrient absorption and relative expression of salt overly sensitive genes exposed to salt stress and AMF inoculation in P.cathayanaNutrient absorption was significantly inhibited and three PcSOS genes showed a distinct expression pattern under salt stress in P.cathayana.Under salt stress,AMF inoculation changed C（15.82%and 7.69%）、P（14.29%and 6.91%）、K⁺（-6.82%and 7.14%）and Ca²⁺（9.02%and 29.86%）contents in female and male roots.The effect of AMF inoculation on relative expression of PcSOS1 and PcSOS3 were significant at 18th hour after salt stress.Meanwhile,AMF inoculation could modulate steady state of ion beam,promote selective absorption of K⁺and Ca²⁺,reduce selective transport of Na⁺and improve imbalance status of K⁺/Na⁺（6.99%and 11.43%）and Ca²⁺/Na⁺（25.08%and 36.79%）ratios in female and male roots by influencing relative expression of PcSOS genes to enhance salt tolerance.