The Study Of Biological Control Against Bacterial Fruit Blotch By Acidovorax Avenae Subsp Citrulli

Bacterial fruit blotch caused by Acidovorax avenae subsp citrulli occurred in most wartermelon-producing countries in the world. It is one of the most destructive diseases on the wartermelon industry, caused a huge serious loss. The pathogen of this disease can survive in the seed for a long time and it was difficult to sleeve. So that is the reason why this disease is very difficult to control. Till now, an efficient resistence cultivar is absence. And although traditional chemical control methods have some efficacy, it can bring pollution on environment and be harmful to human and livertock. Therefore, biocontrol method becomes the hotspot of research of Bacterial fruit blotch control.The antagonistic bacteria we used were selected from our lab’s strains library. According to their biocontrol efficiency to kinds of plant disease, the40strains that have better biological efficacy were selected. Finally,6potential strains were screened out for next greenhouse study and field experiments refer to the results of antagonistic activity, enzyme activity and the first greenhouse biological efficiency. To verificate the strains’ biological efficiency, we developed the second greenhouse experiments. From the results, we can see that6antagonistic bacteria had significant biocontrol efficacy (45.72%-56.59%) against Acidovorax aveae subsp. citrulli. Bacillus amyloliquefaciens54showed the highest biocontrol efficiency which was56.59%. The6selected strains also can promote plant growth effectively, with12.50-130.43%biomass increase. The6antagonistic bacteria’s colonization were to103CFU/g fw after45d. According to the results we got, we chose the Bacillus amyloliquefaciens54for seed soaking experiment, the biocontrol efficiency was86.52%. In the field experiment, they got the biocontrol efficiency about36.86%-54.12%. Bacillus amyloliquefaciens54was the best antagonistic bacteria against Acidovorax aveae subsp.citrulli, showed the same results as the greenhouse experiments. The fruits’biomass and quality were also rised. And the Bacillus amyloliquefaciens54teatment showed the best result. It has higher biocontrol potency.In addition, biocontrol effects of micro-preparation "Shu De Kang" which is composed of two strains of Bacillus and one strain of Serratia on bacterial fruilt blotch (BFB) of watermelon was evaluated under greenhouse conditions through some parameters such as biocontrol efficacy, biomass, content of chlorophyll and nutritional elements in watermelon leaves. Results revealed that biocontrol efficacy was40.8%and the biomass of watermelon seedlings increased about51.0%in the "Shu De Kang" treatment compared to the control. Increasing contents of chlorophyll A, chlorophyll B, chlorophyll and N, P, K in the leaves of watermelon seedlings were also observed in "Shu De Kang" treated plants, the specific data was14.2%,42.2%,21.1%and22.5%,33.4%,29.6%, respectively. And these results indicated its beneficial effects on watermelon.