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Poster: Biology & Disease Mgmt: Biological Control


Microscopic analysis of parasitism mode of action by bacterial biological control agents on Cornus florida powdery mildew
M. MMBAGA (1) (1) Tennessee State University, U.S.A.

Three bacterial isolates, Baccillus( sp., Stenotrophomonassp. Serratia( sp. were previously identified as naturally occurring biological control agents (BCA) for powdery mildew in Cornus florida . The interaction between these BCA’s and powdery mildew fungus was studied using scanning electron microscopy (SEM) and detached leaf technique. Four replicates of similar leaves were infected with powdery mildew, sprayed with BCA’s , incubated for 3h, 6h, 15h, 48h and 5 days, then fixed overnight using formalin acetic acid alcohol and stored at 4 °C untill SEM imaging was done. The SEM micrographs showed the three BCA’s colonizing powdery mildew spores and hyphae. The BCA’s displayed the ability to enter and lyse powdery mildew spores and hyphae; the (Baccillus( sp. lysed and destroyed mycelial structures completely within 48h; others took longer. The BCA’s multiplied on the leaf surface and inside powdery mildew spores and hyphae. The three BCA’s did not interfere with other microbes on the leaf surface; this displayed potential specificity to powdery mildew and potential preservation of other naturally occuring microflora. The collapsed conidia and lysed hyphae suggested antifungal compounds that caused structural damage may be involved. These observations confirm that the three naturally occuring BCA’s may provide a buffering effect against powdery mildew and a resource for powdery mildew management and reducing conventional fungicides usage