Ecological Regulation Of Maize Colonized By Different Morphological Of Beauveria Bassiana Spores On Ostrinia Furnacalis

Beauveria bassiana is a kind of entomogenous fungi.In recent years,it has been found that the colonization of B.bassiana in plants has a series of positive effects on the growth of host,and they can improve plant resistance against insects.According to different culture conditions,B.bassiana has three different forms of spores:aerial conidia,blastospores and submerged conidia.Yet a clear understanding of whether the three infective unit types have different effects on plants,especially in the context of their endophytic colonization of application is still lacking.In order to understand the effects of different morphological of B.bassiana on herbivorous insects,a maize-B.bassiana symbiote was constructed by root-irrigation method and fed to the larvae of Ostrinia furnacalis,the response of insect weight,food intake,survival rate to different infective unit types in B.bassiana-maize symbionts was observed,and the expression of key O.furnacalis defense genes and protective enzymes were recorded to understand the ecological regulation mechanism of endophytic B.bassiana on O.furnacalis.The main results of this study are as follows:1.B.bassiana colonized in maize indirect inhibit the growth and development of O.furnacalis.The mortality of corn borer fed on the aerial conidia treatment（AC）reached 100%on the 15^th day after inoculation,while that of the blastospores treatment（BS）reached 100%on the 9^th day after inoculation,the results of leaf consumption showed that the control group was significantly higher than the B.bassiana treatments,and the AC treatment has the lowest leaf consumption.The results of body weight showed that different conidia of B.bassiana could inhibit the body weight against 2^nd～4^th instar larvae of O.furnacalis,and the body weight of larvae treated with different B.bassiana treatment was lower than that in control.2.The leaves inoculated with both aerial conidia and blastospores of B.bassiana showed significant inhibition and avoidance effect to the larvae of O.furnacalis.In the 48-hour choice experiment of O.furnacalis,the selective rate of leaves treated with B.bassiana was significantly lower than that in control,and BS treatment has the lowest selective rate.In the olfactory selectivity test of neonate and 3rd instar larvae of O.furnacalis,the olfactory selectivity response rate in control group was significantly higher than that in both AC and BS treatment（p<0.01）,while the olfactory selectivity coefficients of neonate and 3rd instar larvae of Asian corn borer were>0 for control group and<0 for BS and AC,which proved that Asian corn borer larvae had negative tendency to taste source substances for AC and BS treatment.3.Both aerial conidia and blastospores of B.bassiana couldregulate resistance-related genes of O.furnacalis.Two peptidoglycan recognition proteins gene PRPS and PRPB,two ACB transporters gene in B.bassiana treated induced O.furnacalis were identified by quantitative real-time PCR,the relative expression levels of cadherin gene were up-regulated,and the relative expression levels of cytochrome P450 gene,UDP-glucuronosyltransferase gene and Heat shock protein gene were down-regulated.4.The activities of superoxide dismutase（SOD）,catalase superoxide dismutase（CAT）and peroxidase enzyme（POD）in the larvae of O.furnacalis were inhibited after feeding on the colonized leaves of B.bassiana.These results indicated that the body resistance of insects could lead to decreased by indirect feeding on B.bassiana.In conclusion,the colonization of maize by different forms of B.bassiana had negative effects on the growth,development and feeding behavior of O.furnacalis.B.bassiana colonized in maize plants and regulated the resistance genes and protective enzyme activities of insects.In this study,we further explored the interactions of entophytic B.bassiana with plants and insects,and clarified the mechanism of colonization and plant insect resistance enhancement of B.bassiana from the perspective of changing insect resistance,it is of great significance for the rational utilization of entomopatogens fungi in biological control.