دانشگاه اصفهان زیست شناسی میکروبی 3060-7647 14 55 2025 11 22 The combined effect of light spectra and antagonistic bacteria in inhibiting the growth of Alternaria brassicicola The combined effect of light spectra and antagonistic bacteria in inhibiting the growth of Alternaria brassicicola 7 20 29059 10.22108/bjm.2024.142657.1611 FA Ehsan Rezaei Department of Plant Protection, College of Agriculture, Razi University, Kermanshah, Iran Rohallah Sharifi Department of Plant Protection, College of Agriculture, Razi University, Kermanshah, Iran Saeed Jalali Honarmand Department of Plant Production and Genetic, Razi University, Kermanshah, Iran Journal Article 2024 08 31 Plant growth-promoting rhizobacteria and their metabolites are considered alternatives to chemical pesticides for managing plant diseases. Additionally, light spectra directly affect plant growth and response to stress, as well as the growth and physiology of plant-associated bacteria and fungi. This study aimed to investigate the role of different light spectra on the growth of beneficial bacteria and pathogenic fungi<strong> </strong>and their antagonistic relationships. This research investigated the effect of full spectrum, red, blue, far-red, UVA, green light and dark conditions on the growth of the antagonistic bacterium <em>Bacillus pumilus</em> INR7 and the plant pathogenic fungus <em>Alternaria brassicicola</em> and the interaction between these two micro organisms under laboratory conditions. The results showed that the light spectra significantly affected the growth of the antagonistic bacterium. Green light had the greatest effect, while UVA had a small effect on the population growth of the bacterium. The light spectra also affected the growth and spore production of A. brassicicola. Blue light increased colony growth, while dark conditions reduced it in the pathogenic fungus. UVA, red, green and blue light showed no significant differences compared to the full spectrum in spore production, dark conditions reduced the spore population. Conversely, UVA increased growth, whereas dark conditions reduced growth of A. brassicicola in the inhibition halo test. Furthermore, green light had the greatest effect and dark conditions the least effect on mycelial growth of A. brassicicola in the presence of volatile compounds from the antagonistic bacterium. The results of these experiments showed that light spectra can influence the physiology of beneficial bacteria and pathogenic fungi, affecting bacterial populations, fungal growth, sporulation rates and their interactions. Plant growth-promoting rhizobacteria and their metabolites are considered alternatives to chemical pesticides for managing plant diseases. Additionally, light spectra directly affect plant growth and response to stress, as well as the growth and physiology of plant-associated bacteria and fungi. This study aimed to investigate the role of different light spectra on the growth of beneficial bacteria and pathogenic fungi<strong> </strong>and their antagonistic relationships. This research investigated the effect of full spectrum, red, blue, far-red, UVA, green light and dark conditions on the growth of the antagonistic bacterium <em>Bacillus pumilus</em> INR7 and the plant pathogenic fungus <em>Alternaria brassicicola</em> and the interaction between these two micro organisms under laboratory conditions. The results showed that the light spectra significantly affected the growth of the antagonistic bacterium. Green light had the greatest effect, while UVA had a small effect on the population growth of the bacterium. The light spectra also affected the growth and spore production of A. brassicicola. Blue light increased colony growth, while dark conditions reduced it in the pathogenic fungus. UVA, red, green and blue light showed no significant differences compared to the full spectrum in spore production, dark conditions reduced the spore population. Conversely, UVA increased growth, whereas dark conditions reduced growth of A. brassicicola in the inhibition halo test. Furthermore, green light had the greatest effect and dark conditions the least effect on mycelial growth of A. brassicicola in the presence of volatile compounds from the antagonistic bacterium. The results of these experiments showed that light spectra can influence the physiology of beneficial bacteria and pathogenic fungi, affecting bacterial populations, fungal growth, sporulation rates and their interactions. https://bjm.ui.ac.ir/article_29059_020ed22a9220da9d69c021b8ac582483.pdf