Striking Similarities Between Botrytis cinerea From Non-agricultural and From Agricultural Habitats

Investigations into life history of microorganisms that cause plant diseases have been limited mostly to contexts where they are in interaction with plants, and with cropped or otherwise managed vegetation. Therefore, knowledge about the diversity of plant pathogens, about potential reservoirs of inoculum and about the processes that contribute to their survival and adaptation is limited to these contexts. The agro-centric perspective of plant pathogen life histories is incoherent with respect to the capacity of many of them to persist as saprophytes on various substrates. In this context we have investigated the ubiquity of the broad host range necrotrophic fungus Botrytis cinerea, outside of agricultural settings and have determined if the populations in these natural habitats can be distinguished phenotypically and phylogenetically from populations isolated from diseased crops. Over a period of 5 years, we isolated B. cinerea from 235 samples of various substrates collected in France including rainfall, snowpack, river, and lake water, epilithic biofilms in mountain streams, leaf litter and plant debris, rock surfaces, bird feathers and healthy wild plants from outside of agricultural fields. All substrates except rock surfaces harbored B. cinerea leading us to establish a collection of purified strains that were compared to B. cinerea from diseased tomato, grapes and various other crops in France. Phylogenetic comparisons of 321 strains from crop plants and 100 strains from environmental substrates based on sequences of 9 microsatellite markers revealed that strains from crops and the environment could not be distinguished. Furthermore, the genetic diversity of strains outside of agriculture was just as broad as within agriculture. In tests to determine the aggressiveness of strains on tomato stems, the mean disease severity caused by strains from environmental substrates was statistically identical to the severity of disease caused by strains from tomato, but was significantly greater than the severity caused by strains from grape or other crops. Our results suggest that highly diverse populations of this plant pathogen persist outside of agriculture in association with substrates other than plants and that this part of their life history is compatible with its capacity to maintain its potential as plant pathogen

The efficacy of biocontrol against<em> Botrytis cinerea</em> on tomato depends on the strain of the pathogen

International audienc

Efficacy of <em>Streptomyces</em> spp. strains against different strains of <em>Botrytis cinerea</em>

International audienceGrey mould caused by the fungus Botrytis cinerea is an economically important disease in numerous crops. Biocontrol is a promising method to control the disease. Species of Streptomyces are potential biological control agents since they are ubiquitous in the environment and many of them produce various secondary metabolites with diverse biological activities including the ability to inhibit this plant pathogenic fungus. Strains RM-1-138 and RL-1-178 of S. philanthi and SS-2-243 of S. mycarofaciens, isolated from the rhizosphere soil of chili peppers grown in southern Thailand, have shown a good efficacy to control Sclerotium roljsii, Ralstonia solanacearum and Rhizoctonia solani but their effect against B. cinerea is not known. In this study we evaluated the efficacy of the three strains of Streptomyces spp. against B. cinerea in vitro and on tomato plants. Results indicated that the three strains inhibit the growth of B. cinerea in Petri plates and have a significant protective efficacy, although variable between strains of Streptomyces spp., against B. cinerea on tomato plant. To assess the possible variability in susceptibility to these antagonistic strains in populations of B. cinerea, the protective efficacy of these bacteria were evaluated against 41 strains differing in their geographic origin, host of isolation and level of aggressiveness. Results based on confrontation tests in Petri plates suggest a diversity in the sensitivity of the different strains of B. cinerea to these biological control agents. The relevance of these results to ensure durability of the efficacy of these biological control agents will be discussed

Geographic structure of Botrytis cinerea populations from vegetable greenhouses in southern France

National audienc

Biological control of tomato gray mold caused by Botrytis cinerea by using Streptomyces spp.

Streptomyces is a genus known for its ability to protect plants against many pathogens and various strains of this bacteria have been used as biological control agents. In this study, the efficacy of Streptomyces philanthi RM-1-138, S. philanthi RL-1-178, and Streptomyce mycarofaciens SS-2-243 to control various strains of Botrytis cinerea was evaluated both in vitro and in vivo. In vitro studies using confrontation tests on PDA plates indicated that the three strains of Streptomyces spp. inhibited the growth of 41 strains of B. cinerea. Volatile compounds produced by Streptomyces spp. had an influence on the growth of ten strains of B. cinerea while its culture filtrate at low concentration (diluted at 10−3) showed a complete inhibition (100%) of spore germination of B. cinerea strain BC1. A significant protection efficacy of tomato against B. cinerea was observed on both whole plant test (57.4%) and detached leaf test (60.1%) with S. philanti RM-1-138. Moreover, this antagonistic strain had a preventive and a curative effect. These results indicated that S. philanthi RM-1-138 may have the potential to control gray mold caused by B. cinerea on tomato but further work is required to enhance its efficacy and its survival in planta

The efficacy of biocontrol against<em> Botrytis cinerea</em> on tomato depends on the strain of the pathogen

International audienc

Geographic structure of Botrytis cinerea populations from vegetable greenhouses in southern France

National audienc

Relationship between the aggressiveness of<em> Botrytis cinerea</em> on tomato and the efficacy of biocontrol

Communication orale au 12. IOBC-WPRS Meeting of the working group "Biological control of fungal and bacterial plant pathogens". Biocontrol of plant pathogens in sustainable agriculture, Reims, France, 2012/06/24-27International audienceThe development of BCAs represents an attractive alternative to fungicides for the protection of crops against plant pathogens but the durability of this method has not been studied in details. The objective of the present work was to estimate the risk of loss of biocontrol efficacy towards Botrytis cinerea, by evaluating the sensibility of various isolates of the pathogen to the biocontrol agent Microdochium dimerum. The protective efficacy of M. dimerum was evaluated on tomato plants against 41 strains of B. cinerea differing in their geographic origin and host of isolation. To this end, whole tomato pruning wounds and detached stem sections were concomitantly inoculated with B. cinerea and with M. dimerum. Lesion expansion was recorded daily from the 3rd to the 7th day after inoculation. Due to the very high level of efficacy against all tested strains of B. cinerea when M. dimerum was used at the recommended dose, it was necessary to reduce the dose of application 10-fold to assess the diversity of sensitivity of B. cinerea to this BCA. In these conditions, a wide range of sensitivities were observed among strains of the pathogen tested with protection levels ranging from 0 to 100% (mean = 53 ± 4%; median = 49%). A correlation was observed between the level of aggressiveness of a strain to tomato and its sensitivity to the biocontrol agent (assessed by the protection level). It reveals the importance of considering several strains of the pathogen when screening for biocontrol agents, to obtain a good representation of the pathogen population and thus take into account the potential durability of biocontrol