Effects Of Arbuscular Mycorrhizal Fungi Colonization On Growth Of Populus Pseudocathayana×deltoides And Feeding Adaptability Of Lymantria Dispar

Arbuscular mycorrhiza fungi（AMF）has been gradually applied to the comprehensive control of economic crop pests in order to improve the growth and development of plants,and has achieved some control benefits.In addition,whether AMF colonization can improve the insect resistance of trees has become a hotspot of current research.It provides theoretical basis for studying the application of AMF on forest growth promotion in and forest herbivore resistance.In this study,1-year-old Qingshan poplar（Populus pseudo-cathayana×P.deltoides）and spongy moth（Lymantria dispar）larvae were used to study the effects of Glomus intraradices（GI）and G.mosseae（GM）on the growth,development and insect resistance of Qingshan poplar,and to judge the adaptability of spongy moth to mycorrhizal poplar by the growth and development of spongy moth,food utilization and digestive enzyme detoxification enzyme activities.The results are as follows:（1）Influence on the growth and development of Qingshan poplar.The plant height and aboveground biomass in GI group were significantly lower than those in the control group,while the underground fresh weight was significantly higher than that in the control group.The plant height,root length,aboveground and underground biomass were significantly increased in GI group.The plant height,root length,fresh weight and dry weight of underground part of Qingshan popla were significantly increased in GM group.These results indicated that GI inhibited the growth and GM promoted the growth of Qingshan poplar.（2）Effects on secondary metabolites and chemical defense of poplar leaves.The contents of nitrogen and soluble protein in GI and GM groups were significantly lower than those in control.There was no significant difference in soluble sugar and phosphorus between GI group and control group.The soluble sugar and phosphorus in GM group were significantly higher than those in control group.Total flavonoids of GI was significantly higher than that of the control,and total phenol was significantly lower than that of the control.The lignin content in GM group was significantly higher than that in control group while total phenol and tannin were significantly lower than those in control group.These results indicated that both GI and GM could change the production of secondary metabolites of Qingshan poplar,and GM had inhibitory effect on the production of most secondary metabolites.（3）Effects on growth and development of spongy moth.The effects of GI on the growth of spongy moth were stage specific.Compared with the control,the body weight,body length and head capsule width of spongy moth larvae were significantly increased at the third instar when they fed on the leaves of Qingshan poplar colonized by GI.At fourth instar,the body weight was significantly higher than the control group,body length and head capsule width were higher than the control group but not significantly.Body weight,body length,head and shell width at fifth instar were not significant compared with the control.The weight and head capsule width of larvae in GM group was higher than that in control group,GM can promote the growth and development of spongy moth.（4）Effects on enzyme activities in spongy moth larvae.The amylase activity of GI group was significantly lower than that of the control at the 4^th instar,but there was no significant difference between GI group and the control at the 5^th instar.The amylase activity in GM group was significantly lower than that in control group.Compared with the control group,the protease activity in GI group was not significantly changed,while that in GM group was significantly increased.The carboxylesterase（Car E）activity in GI group was not significantly different from that in control group,while that in GM group was significantly lower than that in control group.Acid phosphatase（ACP）activity in GI group was significantly lower than that in CK group,while GM group was significantly higher than that in CK group.The activity of alkaline phosphatase（AKP）in GI group was higher than that in the control group at age 4and lower than that in the control group at age 5.The GM group was significantly higher than the control group.（5）Effects on food utilization of spongy moth.The food digestion rate of GI group was significantly higher than that of the control group at the 3^rdage,but there was no significant difference between GI group and the control group at the 4^th and 5^th ages while the fourth age of GM group was higher than that of the control group,but there was no significant difference between the third and fifth ages.There was no significant difference in food conversion rate between GI group and control group,GM group was significantly higher than control group at third and fifth instar,while the fourth instar had no significant difference compared with control group.The food utilization rate of GI was significantly higher than in the control group in third age,but there was no significant difference in the fourth and fifth age.The food availability of GM group was significantly higher than that of control group.The results display that GI showed a phasic promoting effect on the food utilization of spongy moth,while GM showed a phasic promoting effect.In conclusion,the effects of GI and GM colonization on the growth and insect resistance of Qingshan poplar are mycorrhizal specificity.GI colonization inhibited the growth of Qingshan poplar and had a neutral effect on its insect resistance.GM colonization significantly promoted the growth of Qingshan poplar and decreased the insect resistance.It is not suitable to apply GI to growth promotion and insect resistance,but GM to improve the production of Qingshan poplar.Therefore,in practical application,appropriate strains should be selected according to the specific needs of forest production process.