内生真菌对氮添加羽茅根际土壤特性和微生物群落的影响

摘要

内生真菌不仅能改变与其共生植物的生理和生长指标,还可通过宿主植物间接对土壤的理化性质和微生物群落结构产生影响.以天然禾草——羽茅(Achnatherum sibiricum)为研究材料,探究在不同施氮水平下,内生真菌的种类对不同基因型的宿主植物根际土壤理化性质和微生物群落产生何种影响.结果表明,内生真菌侵染显著提高了羽茅根际土壤的pH值和微生物总量,但降低了土壤中真菌与细菌的比值.同时,土壤的pH值还受到了内生真菌种类的影响,其中感染Epichlo(e) sibirica的羽茅根际土壤pH显著高于感染Epichlo(e) gansuense-1的羽茅,而感染Epichlo(e) gansuense-2的羽茅根际土壤pH与感染E.gansuensis-1、E.sibirica菌的羽茅相比没有显著差异.另外,内生真菌感染与否、内生真菌种类、施氮量以及宿主植物基因型对土壤总碳、总氮、微生物及碳矿化能力均无显著影响.%Simultaneous infections of host plants with endophytic fungi are common in both natural and agricultural ecosystems.Endophyte-infected (E+) grasses may differ in chemical composition and root exudates from endophyte-free (E-) individuals,and these differences may indirectly affect soil properties and microbial communities in the host grass habitat.In this study,we used as plant material Achnatherum sibiricum,a native grass,naturally infected with two species of endophytes,including Epichlo(e) sibirica and E.gansuensis.E.gansuensis has two morphotypes,E.gansuensis-1 and E.gansuensis-2,of which E.gansuensis-1 exhibits strict vertical transmission,while E.gansuensis-2 can be transmitted vertically as well as horizontally.The objective of this study was to explore the effect of endophyte infection,endophyte species,nitrogen availability,and maternal plant genotype on the physicochemical properties and microbial communities of soil in the A.sibiricum habitat.At the end of a pot experiment,we analyzed the soil total carbon (C) and nitrogen (N),determined soil pH,and estimated the soil C mineralization.Soil microbial biomass and community composition were assayed by using the phospholipid fatty acid (PLFA) technique.In the present study,we found that the soil pH value differed significantly between the E+ and E-treatments (E+ ＞ E-).In addition,the soil pH was influenced by endophyte species:pH in the E.sibirica-infected condition was higher than that in the E.gansuense-1 infected condition,but the difference was not significant with the E.gansuense-2 condition.Endophyte infection significantly improved the total amount of rhizosphere microorganisms but reduced soil bacterial:fungal ratio.Endophyte status and species,nitrogen addition,and maternal plant genotype had no significant effects on soil total carbon (C) and nitrogen (N),rhizosphere microorganisms and C mineralization ability.This study suggested that endophyte infection could alter soil pH and microbial community structure,and endophytic fungi may change soil total C and N with more available nitrogen or in the long-term.These conclusions provided some experimental basis for further understanding the complex symbiotic relationship between fungal endophytes and native grasses and its role in ecosystem C and N cycling.