The Antagonistic Mechanism Of Endopytic Bacteria Against Fusarium And Verticillium Wilt Of Cotton

We chose seven different strains of endophytic bacteria which had good inhibitory function on Fusarium and Verticillium wilt of cotton as test material to study the resistance mechanisms of endophytes against disease fungus from the production of cell wall degrading enzymes, siderophore and induced systemic resistance.The test results of sifting out the wall degrading enzymes-secreting bacteria showed that all strains neither produce dextranase nor chitinase, but color circle can be detected in the cellulose test plates of strain HS-6 and HS-7. But cellulose is not the main component of cell walls in Fusarium oxysporum and Verticillium dahliae, so it is not significant for the suppression of pathogentic fungi.The antagonism test result of several siderophore-producing entophytic bacillus against Fusarium and Verticillium wilt of cotton showed that strain HS-1, HS-2, HS-3 and HS-4 in MSA medium produced fluorescence siderophores and the ability of siderophore production in MSA medium was higher than CAS medium; Wavelength scan showed that four strains produced carboxylic acid type siderophore in the both media; The siderophore had a strong inhibiting effect on Fusarium of cotton wilt. With increasing concentration of iron, the siderophores secretion was reduced and the inhibiting effect weakened. However, there seemed to be no inhibitory effect on Verticillium wilt of cotton.The test result about systematic resistance of cotton induced by endophytes showed that endophytic bacteria can increase disease resistance after the addition of fungal pathogen invasive cotton and the result also showed induced enhancement of host defense related activity, simultaneously enhanced Vc production of host, decrease in MDA content and high performance the role of induced resistance. This effect could inhibit on the injury of pathogenic fungi to host cell and gradually repaired the damage. After the invasion of fungi to be inhibited, resistance-related enzyme activity and the content of Vc and MDA were gradually returning to normal.