Effects Of Arbuscular Mycorrhizal Fungi On The Growth And Disease Resistance Of Invasive Clonal Plants

Alien invasive plants affect natural environment,social economy and become a serious ecological problem.Previous studies on invasion ecology have focused more on the plant to plant level.However,recent studies have shown that the excellent contribution of soil micro-organisms Arbuscular mycorrhizal fungi(AMF).AMF play an important role for the success of invasive plants which profoundly influence not only the growth and nutrient uptake,but also the biotic stress responses.Therefore,this graduate thesis takes the invasive clonal plants Wedelia trilobata and Alternanthera philoxeroides as the research species,and selects Glomus mosseae(GM),Glomus versiforme(GV)and combined with clonal integration,aims to reveal the relationship between AMF and disease resistance of invasive clonal plants.The main results are as follows:(1)After inoculated with two species of AMFs under three different nutrient conditions,it was found that AMF can form a symbiotic relationship with the invasive clonal plant W.trilobata.Higher colonization rate and abundance under low nutrient conditions was observed.Moreover,there are significant differences in the colonization rates between different types of AMF.The colonization rate of GM is significantly lower than that of GV.For A.philoxeroides,the colonization rate of GV is low than W.trilobata even under low phosphorus nutrition.This result indicates that AMF has host specificity,that is,even the same kind of AMF will have different colonization rate for different host species.(2)Keep clonal integration significantly reduced the colonization rate of GV.Moreover,invasive clonal plants have a "division of labor" phenomenon which keep clonal integration.The basal ramets tend to allocate more biomass to underground fraction,while the apical ramets tend to distribute biomass to the aerial parts.(3)In the disease resistance experiment,the addition of GV can reduce the infection area and infection rate of the Rhizoctonia solani(RS).For A.philoxeroides,the addition of GV can also reduce the area of RS.In addition,keep clonal integration can effectively alleviate the damage to invasive clonal plants.Moreover,the invasive clonal plants which keep theclonal integration and inoculated with GV,acquired higher disease resistance.(4)After infected with RS,hormone content of Abscisic acid(ABA)and Gibberellin(GA)was higher in W.trilobata inoculated with GV.However,for the invasive clonal plant A.philoxeroides,inoculation of GV reduced the levels of ABA,GA and Jasmonic acid(JA)in plants.The defense responses of invasive plants are alleviated by the action of AMF to achieve enhanced disease resistance.The above results indicate that AMF can form the symbiotic relationship with invasive clonal plants,especially under low-nutrient environments.Clonal integration and AMF can help invasive clonal plants increase nutrient uptake and promote growth.Also,AMF and clonal integration can enhance the plant disease resistance by regulating the content of hormones in plants,and benefit survival advantage under pathogenic stress.