Different wavelengths of visible light influence the conidial production and tolerance to ultra-violet radiation of the plant pathogens Colletotrichum acutatum and Fusarium fujikuroi

The effects of the visible light wavelengths on germination, mycelial radial growth, and conidial production of the plant pathogens Colletotrichum acutatum and Fusarium fujikuroi were studied. Both fungi were grown on potato dextrose agar medium (PDA) in the dark (control) or on PDA under continuous white, blue, green or red light. In addition, the conidia from each treatment were exposed to UV radiation. The germination and growth of both plant pathogenic fungi were not affected by any of the treatments. C. acutatum produced more conidia when the fungus grew under white and red light. F. fujikuroi produced more conidia in the dark. The tolerances to UV radiation of conidia produced on different light and dark treatments differed for both C. acutatum and F. fujikuroi . Conidia of C. acutatum were at least 30% more tolerant to UV radiation when they were produced under white light than under blue and green light and at least 20% more tolerant than conidia produced in the dark. Conidia of C. acutatum produced under red light were the least tolerant. Conidia of F. fujikuroi produced under white and blue light were at least 30% more UV tolerant than conidia produced in the dark, green, and red light. In conclusion, no differences were found for germination and growth for both fungi under different light regimes and dark; however, significant differences occurred both in production and UV radiation of conidia.