Diversity Of Microbial Community In Rhizosphere Soils Of Lycium Barbarum L. And Influence Of Arbuscular Mycorrhizal Fungi Salt Tolerance

PCR-DGGE technique was applied to analyze the arbuscular mycorrhizal?AM?colonization rate and microbial community in the rhizosphere of Lycium barbarum L.different in tree ages and sampling sites.The relationships among AM colonization status,edaphic factors and community diversities were also assessed.A pot experiment was conducted to study the interactive effects of AM fungi and potassium application of Lycium barbarum L.responding to salt tolerance.The main results as follows:1.Diversity of microbial community in rhizosphere soils of Lycium barbarum L.in different tree ages.Readily available P,pH,readily available K,and nitrate N in rhizosphere soil of Lycium bararum L.were significantly different in different tree ages?5 years,10 years,15 years,and24 years?,and the readily available P,readily available K,and nitrate N reached maximum at10 years.AM colonization remained stable,while spore density showed significant difference amoung different ages.According to the results of sequence analysis of DGGE dominant bands,the diversity index of the rhizosphere community did vary much between the fields at different ages,The diversity of AM fungi from the rhizosphere soil of Lycium barbarum L.was significantly reduced in 10 years?compared with that of 5 years?.The diversity of bacteria from the rhizosphere soil of Lycium barbarum L.was significantly reduced in 15years?compared with that of 10 years?.The microbial diversity of rhizosphere soil decreased with the increment of ages.The correlation analysis showed that spore density was significantly positive correlated with ammonium N.Species richness was significantly positive correlated with the readily available K and nitrate N,positively correlated with pH.Evenness index was positively correlated with pH,significantly negative correlated with the readily available P,and ammonium N.Furthermore,tree ages affected rhizosphere soil AM fungi community characteristics to some extent.2.Diversity of microbial community in rhizosphere soils of Lycium barbarum L.at different sampling sites.Lycium barbarum L.No.1 all were infected by AM fungi.Edaphic factors and spore density were different in six sampling sites?Xiaochitang,Shangqiao,Qidui,Liudui,Changtan ang Miaopu?.AM fungi diversity indices in six sampling sites were obviously different.Shannon-Weiner index was the highest in Qidui,Evenness index was the highest in Shangqiao,Simpson index was the highest in Xiaochitang and Qidui.The dominant AM fungi were from genus Glomus and Funneliformis and the dominant bacteria were from genus Pseudomonas.The correlation analysis showed that the ammonium N was positively correlated with Species richness,Shannon-Weiner index,Evenness index and Simpson index.Species richness was negatively correlated with pH.Simpson index was significantly negative correlated with pH,and was positively correlated with readily available P and nitrate N.Mycorrhizal colonization rate was positively correlated with nitrate N.Nitrate N,pH and readily available K had significant difference in three sampling sites?Liudui,Changtan and Shangqiao?,and the AM fungi infection rate and spore density were the highest in Liudui.The dominant AM fungi were from genus Glomus and the dominant bacteria was from genus Pseudomonas.The correlation analysis showed that Mycorrhizal colonization rate was negatively correlated with nitrate N and ammonium N.Species richness and Shannon-Weiner index were significantly positive correlated with readily available K,nitrate N and ammonium N,and were significantly negative correlated with pH.Evenness index was significantly positive correlated with pH and readily available P,and was negatively correlated with nitrate N and ammonium N.Spore density was significantly negative correlated with pH and readily available P.3.The influence of AM fungi and potassium application of Lycium barbarum L.salt toleranceAM fungi promoted the growth of Lycium barbarum L.Mycorrhizal colonization rates,dry weight of shoot and root gradually increased with the increment of potassium application under salt stress,reaching the significant level at 4 mM K₂SO₄,improved up 16.1%,24.2%and 27.1%by comparing to the 0 mM K₂SO₄ respectively under 200 mM NaCl.?PSII,Fv?/Fm?and qP decreased and AM fungi increased the chlorophy fluorescence of Lycium barbarum L under salt stess.Potassium application dramatically increased the Fv/Fm,?PSII,Fv?/Fm?and decreased the NPQ,and had no significant difference at 4 mM K₂SO₄,which demonstrated that the potassium of moderate concentration is beneficial to the photosynthesis of Lycium barbarum L.AM fungi promoted antioxidant enzymes of Lycium barbarum L.The SOD,POD activities were dramatically enhanced along the rising of potassium application under salt stress,reaching the significant level at 4 mM K₂SO₄,and the inoculational plant was higher than the non-inoculation.CAT activity of the non-inoculation plant significantly increased,and the inoculation plant had rising tread,but was only significantly improved at 4 mM K₂SO₄ level under 200 mM NaCl.Therefore,AM fungi and potassium application enhanced the antioxidant enzymes,and protect the antioxidant system of Lycium barbarum L.Salt stress promoted K⁺and Na⁺competition in plant cells,Na concentration increased,K concentration and K/Na ratio decreased.Potassium application increased the K/Na ratio,which demonstrated that appropriately increasing potassium content can alleviate the potassium deficiency caused by salt stress and promoted the growth of Lycium barbarum L.