Biological management of gray mold in pot roses by co-inoculation of the biocontrol agent Ulocladium atrum and the mycorrhizal fungus Glomus mosseae

In pursuit of a biological disease and stress management strategy for ornamentals, a three-factorial experiment was performed to examine the effects of plant darkness stress, Ulocladium atrum and Glomus mosseae on gray mold caused by Botrytis cinerea and plant vigour in potted roses. While darkness stress significantly enhanced gray mold, U. atrum negated the stress effect, reducing disease incidence to comparable levels in both stressed and non-stressed plants. G. mosseae interacted positively with U. atrum under non-stress conditions and negatively in darkness. G. mosseae significantly reduced non-specific leaf wilt incidence. Darkness significantly reduced the number of leaves formed above the pruning stub; U. atrum efficiently counteracted this effect, but had no effect under non-stress conditions. G. mosseae and U. atrum additively increased the total number of leaves per plant, and increased plant top dry weight. However, G. mosseae had no effect on dry weight under stress conditions. G. mosseae root colonization increased significantly when U. atrum was applied, but only under normal light conditions. In conclusion, a biological approach combining a foliar biocontrol agent and an arbuscular mycorrhizal fungus for gray mold protection seems promising.