Hamidreza Alizadeh

Alternaria alternata is an important plant pathogen that can cause disease in over 360 plant species. Control of fungal diseases caused by Alternaria alternata is typically done using chemical pesticides. However, the use of chemical pesticides can pose risks to human health and the environment. Biological control is an alternative method for controlling fungal diseases that uses live agents such as bacteria and fungi. In this study, the effect of 8 bacterial isolates on Alternaria alternata was investigated using dual culture and volatile compounds. The results showed that 5 bacterial isolates Bacillus amyloliquefaciens UJB 30, Pseudomonas fluorescens UJB 28, Pseudomonas fluorescens UJB 19, Bacillus velezensis UJB 20, and Bacillus subtilis UJB 15 were able to create a inhibition zone. Investigation of the antagonistic effect of the isolates using the dual culture method showed that isolates Bacillus amyloliquefaciens UJB 30, Pseudomonas fluorescens UJB 28, Pseudomonas fluorescens UJB 19, Bacillus velezensis UJB 20, and Bacillus subtilis UJB 15 had an effective inhibitory effect on the growth of Alternaria alternate. Isolate Bacillus amyloliquefaciens UJB 30 produced the highest amount of inhibition halo and volatile compounds. In addition, the bacterial isolates studied produce other antimicrobial metabolites such as hydrogen cyanide, protease, cellulase, amylase, and surfactant. The results of this study suggest that the bacterial isolates have the potential for biological control of plant diseases caused by Alternaria alternata. These isolates could be used as a replacement for chemical pesticides for the control of these diseases.