Endophytic Colonization Of Phaseolus Vulgaris (Fabaceae) By Beauveria Bassiana And Their Effects On Tri-trophic Interaction Between Plant-tetranychus Urticae-predator Phytoseuilus Persimilis

Using insect pathogenic fungi is an important biocontrol strategy to manage pest mites.Many studies have shown that insect pathogenic fungi can also colonize plants,promote plant growth,transfer nutrient,produce metabolites,and protect plants from pests and diseases.In order to investigate the endosymbiotic characteristics of insect pathogenic fungi in plants and their effects on the tertiary nutritional relationship of host plants,pest mites and natural enemies,the colonization of Beauveria bassiana in bean plants and its effects on the tertiary nutritional relationship of beans,Tetranychus urticae and Phytoseiid mites were studied.1.Beauveria bassiana could be used as endosymbiotic fungi in plants and can be inoculated in kidney bean plants.Beauveria bassiana could colonize in different parts(leaves,stems and roots)for 14 and 28 days,and the percentage colonization increased significantly with the inoculation time.Among various inoculation methods,Beauveria bassiana inoculated only by seed treatment significantly promoted the growth of bean plants,and the longer the seed treatment time,the more significant the effect.2.Colonization ability of insect pathogenic fungi in kidney beans was verified by three strains of Beauveria bassiana,one strain of Lecanicillium lecanii and one strain of Isaria fumosorosea.The results showed that all strains of three species could colonize bean plants,however,the colonization rate was different.On the 7th and 14th day,Beauveria bassiana had the highest colonization rates in bean roots,80%and 70%,55%and 50%in stems,55%and 55%in leaves,respectively.3.The effects of Beauveria bassiana colonization on the population of Tetranychus urticae were studied.The results showed that the colonization of Beauveria bassiana significantly prolonged the development time of pre-adult mites and average generation cycle of Tetranychus urticae,and reduced the life span of adult mites,female fecundity,intrinsic growth rate and net reproduction rate.The colonization of bean plants by Beauveria bassiana resulted in negative effects which were harmful to the growth and development of Tetranychus urticae,leading to delayed growth and death of mites.In addition,the results also showed that Beauveria bassiana significantly inhibited the growth of Tetranychus urticae,and had a negative impact on the growth and reproduction of Tetranychus urticae in successive generations.4.The effect of colonization on bean plants by Beauveria bassiana on the higher trophic level organism relationship,i.e.Phytoseiid mites,was determined.The results showed that the colonization of Beauveria bassiana had no significant effect on the survival,development and reproduction of predatory mites.In conclusion,the results of this study indicate that the colonization of insect pathogenic fungi in plants can promote plant growth and protect host plants from phytophagous mites,and has no negative impact on the growth and development of host plants and higher trophic levels of organisms(natural enemies).This study provides a new idea and theoretical basis for the field application of insect pathogenic fungi as endophyte.