Journal of Plant Pathology & Microbiology

Abstract

Biological Control of Potato Brown Leaf Spot Disease Caused by Alternaria alternata Using Brevibacillus formosus Strain DSM 9885 and Brevibacillus brevis Strain NBRC 15304

Ahmed IS Ahmed

Brown leaf spot is one of the prevalent diseases caused by Alternaria alternata in different growing areas of potato worldwide. Eight A. alternata isolates were screened from forty-two isolates collected from different potato growing regions in four Egyptian governorates viz, North Sinai (Baloza), Beheira (El-Nubaria and Wadi El-Natrun), Ismailia (Abu Suweir, Fayed and Tell El-Kebir), Sharqia (New Salheya and El-Husseiniya). The virulence of the isolates was tested based on the Per cent of Disease Index (PDI) which ranged from 28.2% to 70.3% PDI by Alternaria isolates of Baloza and Fayed respectively. Two bacterial strains “Brevibacillus formosus strain DSM 9885, and Brevibacillus brevis strain NBRC 15304 were selected to control of A. alternata. The bacterial strains have a higher inhibitory effect on mycelial development and spore germination of A. alternata. To determine the effects of the bacterial strains on disease index and severity, the most virulent of A. alternata isolates were selected for greenhouse experiments where the potato plants were sprayed with bacterial strains individually and mixture treatments. Superior effect of treatments in disease reduction was observed when the two bacterial strains were combined. The effect of leaf age was studied where the leaf position has significant effect on disease progress. The changes of soluble protein in potato leaves due to Brevibacillus strains application were studied. Protein profiling by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the plant treated with mixture of biocontrol agents able to synthesize some new proteins with maximum number of bands followed by treatment by B. formosus strain. The presence or absence of the bands in protein profiling might be responsible for resistance response against A. alternata in potato. The present work suggests that use of B. formosus strain DSM 9885, and B. brevis strain NBRC 15304 could be considered as potential management tools for reducing the impact of A. alternata causing brown leaf spot disease on potato.