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Use of Selenate-Resistant Strains as Markers for the Spread and Survival of Botrytis cinerea Under Greenhouse Conditions

Botrytis cinerea marked strains combining traits of fungicide resistance or sensitivity (carbendazim, iprodione) with resistance to selenate were created and assessed for use in studying the dispersal of B. cinerea and its survival inside plant tissue under greenhouse conditions. Marked strains differed in their ability to cause lesions and to disperse in the greenhouse. A strain that was the most aggressive in infecting plants was also the most successful in spreading across the greenhouse. Following 7 to 14 days of exposure to marked inoculum, about 90% of plants showed quiescent B. cinerea infection with no significant difference between hosts or seasons. However, in a warm season, most of the plants were infected with wild-type B. cinerea, whereas most of the winter-recovered B. cinerea strains were of the marked phenotype, showing the importance of local inoculum from within the glasshouse in winter. The air of the greenhouse contained the same population of marked B. cinerea in warm and in cold periods, whereas the total population was significantly higher in summer. In the warm season, mycelium of B. cinerea inside plant debris lost viability within 3 to 4 months, whereas it stayed viable for 4 months in the winter (December to March) and started to lose viability in April.