Biological Control Of Take-All Disease Of Wheat By Endophytic Bacteria

A serious take-all disease of wheat caused by the soil-borne fungus Gaeumannomyces graminis (Ggt) is prevalent all over the world. Until now, control of take-all has been difficult because of lacking of resistant cultivars and effective fungicide. Take-all is able to be effectively controlled by crop rotation. However, this is not practical and economical in many wheat-producing areas. Since the fluorescent Pseudomonas strains were successfully utilized to controlling take-all by Weller, biological control have been an important method for take-all disease. Endophytic bacteria could play an important role in the host plant, so many successful reports for endophytic bacteria as biocontrol agents have been occurred. But there is a few research about endophytic bacteria to control take-all disease. The objective of our research is to isolate and screen endophytic bacteria from wheat against take-all disease, and to discover the mechanism of the endophytic bacteria against pathogens.(1) The endophytic bacteria were isolated from roots, stems, leaves and immature seeds of wheat in different growth stages. The results showed that there were a lot of endophytic bacteria in wheat tissues. The populations of endophytic bacteria in wheat tissues were about 5.0×10~5cfu(colony forming uint)/g(fresh weight) in average. The significant difference among different tissues and growth stages and fields were found. The numbers of endophytic bacteria were 7.8×10~5cfu/g isolated from wheat roots, 4.8×10~5cfu/g from stems, 3.2×10~5 cfu/g from leaves and 2.8×10~5cfu/g from immature seeds. The populations of endophytic bacteria were significantly difference isolated in different wheat growth stage. The average numbers were 3.1×10~5cfu/g in seeding stage, 5.7×10~5cfu/g in elongation stage and 7.0×10~5 cfu/g in filling stage. The different numbers of endophytic bacteria were obtained in different fields. Also, 51 antifungal endophytic bacteria isolates were trapped by pathogenic fungi Ggt and 45 isolates by Rhizoctonia cerealis. Most of 78 endophytic bacteria isolated by trapping displayed antifungal activities in vitro. Twenty three isolates showed strongly inhibitory activities (inhibition zone>10mm ) against mycelia growth of Ggt, 6 of these isolates from roots, 7 from stems, 9 from leaves and 1 from immature seeds. Twenty isolates revealed strongly inhibitory activities (inhibition zone>10mm ) against R. cerealis, 7 from roots, 5 from stems, 7 from...