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

The mycorrhizal status and soil conditions of Populus cathayana rehder males and females grown at Qinghai province of different tree ages and from arid regions were studied.Using the Illumina Miseq,we tested the fungal and bacterial structures.We also tested the effects of arbuscular mycorrhizal fungi（AMF）inoculation on growth,water condition,photosynthesis,osmotic adjustment and autioxidant enzyme activities.Besides,we investigated the relationship between 2 genders,and the effect of AMF on it.From all these experiments,we discussed the mechanisms of AMF improving drought tolerance,and its potential role in maintaining gender balance of P.cathayana.The main results are as follow:1.Mycorrhizal status and soil conditions of P.cathayana males and females of different agesSoil elements contents,enzyme activities,glomalin contents,AMF spore density,AMF and ectomycorrhizal fungi（EcMF）inoculation rate decreased in deeper layers.The contributions of glomalin to soil organic carbon（SOC）were higher in deeper layers.With increase of tree ages,AMF inoculation of male and female roots increased.AMF spore density of males always increased with age,but this of females decreased from 10y.EcMF inoculation rates of both genders rose first and fall after 3y.So was in glomalin content,but peaked at 10y.But the contribution of glomalin to SOC decreased with age.Soil elements contents and enzyme activities of females peaked earlier than those of males.Principal components analysis（PCA）showed that the greatest difference between 2 genders was at 10y.Available K,nitrate N,ammonium N and SOC content contributed most to soil condition of males,and dehydrogenase activity,AMF spore density,nitrate N and SOC content contributed most to soil condition of females.2.Mycorrhizal status and soil conditions of P.cathayana males and females from different arid regionsThe ratio of females decreased with the decrease of average annual precipitation of 5sites.Mycorrhizal status and soil enzyme activities were higher at surface.AMF and dark separate endophytes（DSE）inoculation rates,AMF spore density,glomalin contents,soil elements contents and enzyme activities decreased with drought level increasing.Males performed better than females in soil elements and enzyme activities.Correlation analysis showed that mycorrhizal status was often significantly positively correlated with soil element contents and enzyme activities,and obviously negatively correlated with electric conductivity（EC）and pH.PCA results showed that the effect of layer was the strongest.Catalase activity,spore density,total glomalin content and nitrate N content can well reflect the soil condition of P.cathayana males and females from Qinghai Plateau.3.Microbial community structures from rhizosphere of P.cathayana males and females from different arid regionsWith the increase of drought level of sites,fungal and bacterial diversities from rhizosphere of P.cathayana males and females rose first and fall later.5 phyla of fungi,380different OTUs were detected.Among these,142 OTUs were only detected from females,while 127 only from males,and 111 from both genders.51,60,73,60 and 43 OTUs were only detected from S1 to S5,respectively.And only 42 OTUs existed in all sites.21 phyla,6396 different OTUs of bacteria were detected.Most of these existed in both genders and 5sites.Non-metric multidimensional scaling（nMDS）showed that the similarities of fungal and bacterial community structures were above 80%,and except in S1,the similarity of fungal and bacterial community structures between males and females were above 90%.Redundancy analysis（RDA）showed that available P,available K,ammonium N contents,EC,pH,moisture content,alkaline phosphatase and catalase activities affected fungal community structure mostly;available P,available K,nitrate N,ammonium N contents,catalase,dehydrogenase and ALP activities,EC and pH affected bacterial community structure mostly.4.Effects of AMF inoculation on drought tolerance of P.cathayana males and femalesUnder well-watered and drought conditions,inoculation rates of males were 95.5%and86.8%,and these of females were 95.4%and 87.0%.Drought stress treatment limited aboveground and underground growth,photosynthesis,chlorophyll fluorescence,relative water content（RWC）,and induced relative electrolyte leakage（REL）,reactive oxygen species（ROS）,malondialdehyde（MDA）,proline contents and peroxidase（POD）activities of both males and females.Under both well-watered and drought stressed conditions,inoculation treatment obviously increased the growth of height（43.05%and 15.08%）,ground diameter（12.14%and 26.46%）,SPAD（2.61%and 10.53%）and leaf area（LA）（22.77%and21.02%）of males.And it also induced male photosynthetic rate（6.27%and 16.11%）,stomatal conductance（22.47%and 17.38%）,intercellular CO₂ concentration（1.29%and4.08%）and evaporation rate（-3.18%and 20.77%）.But its effects on females were indistinctive.Meanwhile,except in female roots,AMF inoculation induced H₂O₂ contents of all parts of both genders.And inoculation treatment also increased proline contents of roots of both genders.Inoculation induced male POD activity,but limited female POD activity.PCA showed that the effects of drought treatment were stronger than inoculation,and the positive effect of inoculation on males was greater than females.5.Effects of AMF inoculation and drought on relationship between P.cathayana males and femalesDrought limited underground and aboveground growth,biomass accumulation and elements contents of males and females,but AMF inoculation alleviated its damage.Under well-watered condition,mixed planting increased inoculated and non-inoculated plants’height（female,5.70%and 16%;male,15.78%and 7.87%）,ground diameter（23.38%and6.97%;14.81%and 11.92%）,SPAD（3.41%and 3.33%;2.26%and 1.16%）,LA（25.81%and 77.97%;1.14%and 15.23%）;under drought conditions,mixed planting increased inoculated and non-inoculated plants’height（27.39%and 20.24%;5.99%and 7.61%）,ground diameter（31.02%and 4.22%;3.23%and 13.14%）,SPAD（6.66%and1.31%;4.69%and 5.75%）and LA（46.67%and 70.34%;18.29%and 5.02%）.Meanwhile,mixed planting increased C,N,P,K,Ca,Mg contents of leaves and roots of both genders.Among mixed planting treatments,AMF inoculation narrowed the gap of growth and elements contents（but Mg）between genders.PCA showed that AMF inoculation had obvious effect on males,no or slight effect on females.Compared with single planting,mixed planting showed positive effects on both genders.