Evaluating Bacterial Agents for Controlling Powdery Mildew and Charcoal Rot

Jeremiah J Sumpter, Tennessee State University


Macrophomina phaseolina is a is widely distributed soil borne fungus causing charcoal rot, a disease of root and stem the soybeans and over 500 other plant species. Management of charcoal rot is limited since currently; there are no fungicides available for effective control, while crop rotation efficiency is compounded by a large host range. Powdery Mildew is one the world’s most encountered plant pathogenic fungi, infecting leaves, stems, flowers and fruits of nearly 10,000 species of angiosperms is Management of powdery mildew is limited to mostly chemical fungicides which are not a sustainable means for controlling the disease. The objective for this study is to use microbial isolates to inhibit the incidence of disease in both charcoal rot and powdery mildew. (1) Each Bacillus isolate inhibited the mycelial growth of M. phaseolina. The percentage growth inhibition (PGI) values for Bacillus vallismortis (Ps) ranged from 75% to 80%, the PGI for Bacillus amyloliquefaciens (Psl) ranged from 78.75% to 81.25%, and Bacillus subtilis (Prt) ranged from 66.25% to 82.50% which was significantly different (P ≤ 0.05) from the control. (2) There were no significant differences among treatments against M. phaseolina. The pathogen was found to be in the lower region of the crop close to the soil line. Disease severity ranged from 2.6(Psl) to 3.4(Prt), The lesion length was all around 2.5cm. The largest soybean plant was 112.1cm(Prt) and the smallest was 97.1cm(Ps). Chlorophyll content was the most interesting and showed the most variance in readings although it showed no significant difference. (3) The bacterial suspensions were able to suppress the incidence of powdery mildew on cucumbers. Starting with disease severity the control showed the most disease in the final reading followed by B17B, IMC8, Ps, Psl, Prt respectively. Leaves actually showing symptoms of infections were highest in Ps and B17B followed by Prt, control, IMC8, Psl respectively. Only one of the treatments showed a significant difference between leaves dead. Total leaves per treatment were around 28 for the high(Ps) and 22 being the low(Psl). By the results given it seems that Psl seemed to lower the incidence of disease the most of all bacterial isolates.

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Recommended Citation

Jeremiah J Sumpter, "Evaluating Bacterial Agents for Controlling Powdery Mildew and Charcoal Rot" (2017). ETD Collection for Tennessee State University. Paper AAI10615608.