Diversity Of Arbuscular Mycorrhizal Fungi (AMF) In Mulberry Rhizosphere And Its Effect On Salt Tolerance Of Hosts

Mulberry(Morus alba L.)is widely distributed in China and has strong adaptability.It is widely used as feed for silkworm rearing and saline-alkali land treatment.However,the continuous planting of mulberry trees has reduced the quality of the site and the yield of mulberry leaves,and salt stress seriously restricted the growth of mulberry orchard in salinealkali land area.In order to investigate the diversity of Arbuscular mycorrhizal fungi(AMF)in mulberry rhizosphere and its effect on salt tolerance,the relationships between AMF and soil nutrients and enzyme activities in mulberry rhizosphere were analyzed in this study.The diversity of AMF in mulberry rhizosphere was studied by morphological identification and high-throughput molecular identification.The effects of AMF on growth,photosynthesis,K/Na balance and other indexes of mulberry under salt stress were studied by pot experiment,and the effect of AMF on salt tolerance of mulberry was revealed.The main research results are as follows:1.Different forest age(5a,10 a,15a,25 a,35a)plantations of mulberry root mycorrhizal status,glomalin content,enzyme activity and soil nutrient content determination results show that with the increase of forest age,mycorrhizal colonization rate,spore density,easily extractable glomalin content,catalase,urease and alkaline phosphatase activity were lower before stable trend.The soil fertility of 15 years of stand age was lower than that of other stand ages,which was the lowest value of the five stand ages.There was an extremely significant positive correlation between the content of easily extractable glomalin and nitrate nitrogen,available potassium,p H,catalase,alkaline phosphatase and urease.There was a significant positive correlation between the easily extractable glomalin content and total glomalin.There was an extremely significant positive correlation between the total glomalin and nitrate nitrogen.2.Eight genera and 26 species of AMF were identified from the rhizospheric soil of mulberry at different ages.Glomus reticulatum and Acaulospora foveate were the dominant species with important values(I)of 50.73% and 52.93%,respectively.A total of 912 OTU were obtained by high-throughput sequencing analysis,belonging to five genera,including Glomus,Gigaspora,Scutellospora,Paraglomus and Diversispora.Glomus was the dominant genus.The α diversity index is different in the rhizosphere soil of mulberry trees of different forest ages.The lowest values of Chao1,Sobs,Shannon index and Simpson index all appeared in plot 35 a.The highest values of Chao1,Sobs and Shannon index appeared in plot 15 A.The results showed that 15 a had the highest diversity of AMF among the five stand ages.Nonmetric Multidimensional Scaling Analysis(NMDS)and ANOSIM differences test showed that there were significant differences in AMF species composition in mulberry rhizosphere soil with different stand ages,and stand ages could significantly affect AMF diversity.3.Rhizophagus intraradices(Ri)of mulberry was highly dependent on salt stress.When the salt concentration was 200 mmol/L,the infection rate and dependence were 79.39% and43.51%,respectively.When the salt concentration was 100 mmol/L,AMF had the greatest effect on the growth and photosynthetic characteristics of mulberry,leaf and stem fresh weight increased by 117.24% and 102.56%,root activity increased by 97.35%,PSII actual photochemical quantum yield(ΦPSII)increased by 85.71%,respectively.Chlorophyll content,net photosynthetic rate,stomatal conductance,transpiration rate and other photosynthetic indexes were significantly increased.Na content in leaves decreased by 27.14%,and K/Na in roots increased by 46.77%.These results indicated that AMF promoted the growth of mulberry by improving root activity,increasing chlorophyll content and photochemical efficiency under salt stress.The salt tolerance of mulberry was enhanced by adjusting the contents of K and Na and K/Na balance in different parts of mulberry.