Effects of UV-B radiation on the antagonistic ability of Clonostachys rosea to Botrytis cinerea on strawberry leaves

Clonostachys rosea is effective to control of Botrytis cinerea on strawberry, although is highly susceptible to ultraviolet radiation and has reduced ability to antagonize a pathogen in solar radiation conditions. The objective of this work was to evaluate the ability of an isolate of C. rosea, previously selected for its tolerant to UV-B radiation, to control B. cinerea on strawberry leaves in controlled experiments. Leaf discs of 1cm diameter were placed on Petri dishes and each received 20μL of a C. rosea LQC 62 concentrations (104, 105, and 106conidiamL−1). They were then exposed to UV-B irradiance 600mWm−2 (0, 2.1, 4.2, and 6.3kJm−2), and after radiation, half of the discs were inoculated with an aliquot of 10μL B. cinerea (105conidiamL−1). The colonization of fungi on the leaf disc was measured with diagrammatic scale formation of conidiophores. The presence and sporulation of C. rosea on leaf disc was influenced by the dose of UV-B radiation and the conidial concentration of antagonist. The incidence and severity of B. cinerea on leaf discs were inversely correlated to presence and sporulation of C. rosea. The growth of the pathogen was higher in the lower C. rosea concentration. The highest concentration of C. rosea (106conidiamL−1) reduced the incidence and severity by 91% and 98% of B. cinerea on strawberry leaf discs. The UV-B radiation reduced the ability of C. rosea to control B. cinerea. The higher dose of UV-B reduced the presence and sporulation of C. rosea by 20% and 42%, respectively. Consequently, the incidence of B. cinerea increased twice and the severity was three-folder higher. Taken together this data means that, for the development of biological control agents based products, the effect of UV-B should be considered on the efficacy studies.