Compared dynamics of grey mould incidence and genetic characteristics of Botrytis cinerea in neighbouring vegetable greenhouses

Abstract : Production of vegetables in southern France often relies on groups of greenhouses located in close vicinity. These crops are commonly affected by grey mould caused by Botrytis cinerea, a fungus known for its ability to produce abundant air-borne inoculum. Possible exchange of inoculum could affect the epidemics developing in neighbouring greenhouses. To test this hypothesis, grey mould incidence was assessed in four successive crops in six unheated polyethylene tunnels located in the Avignon area. On lettuce, the incidence was similar for a given harvest date in two tunnels where this crop was grown four times consecutively. In the four other tunnels, lettuce was grown in alternation with tomato. No grey mould developed on tomato and disease incidence was low on lettuce. One hundred and seventy four strains collected from lettuce in two tunnels were investigated for their genetic diversity, genetic structure and their mating type. Both known mating types of B. cinerea were observed in the tunnels but MAT1-1 was prevalent. The gene diversity of B. cinerea strains was similar in both tunnels. However haplotypic diversity and linkage disequilibrium were substantially higher in one tunnel. We hypothesize that this situation is related to differences in microclimatic conditions in the tunnels. It highlights a possible interest in individualizing disease management in the different tunnels of a given farm.