SURVIVAL AND DISPERSION OF BOTRYTIS CINEREA IN MEDITERRANEAN GREENHOUSES
R RAPOSO1, C ALFONSO1, T URRUTIA2, V GOMEZ2 and P MELGAREJO1
1Plant Protection Department, INIA, Ctra. Coruna Km. 7, 28040 Madrid, Spain; 2Laboratorio de Sanidad Vegetal, La Mojonera, 04004 Almeria, Spain
Background and objectives
Botrytis cinerea is an important disease in unheated plastic greenhouses in Mediterranean areas. It causes grey mould disease in winter vegetable crops. Epidemics usually begin in November and last until February-March. Crops are then harvested and sometimes new crops are grown in spring. The life cycle of B. ;cinerea during summer in these conditions is unknown. Inocula may come from inside or outside the greenhouses as mycelia, conidia or eventually sclerotia, although formation and development of sclerotia have not been reported in Mediterranean areas. The occurrence of sexual reproduction is unknown, despite both mating types (MATI-1 and MATI-2) being present in these populations . Studies on the population structure of B. ;cinerea may add useful information to address these questions. Our objectives are to know how B. ;cinerea 'over-summers' in these conditions and which are the main inoculum sources and how they disperse.
Materials and methods
Two experiments were conducted in commercial greenhouses in Almeria, Spain, during summer 1995 and 1997. Sclerotia and mycelia (in stems and leaves) of 14 field isolates were placed inside and outside of a greenhouse at the beginning of June and samples were taken monthly to check their viability and pathogenicity until the onset of the epidemic. In addition, an experiment was done in vitro to check the viability and pathogenicity of sclerotia and mycelia in stems and leaves at different temperatures. Primary sources of inocula (sclerotia, apothecia, mycelia and conidia) were looked for inside and outside commercial greenhouses. Spore traps were placed outside and inside the greenhouse to determine the dynamics of conidia.
To determine the population structure, a random sample of 141 isolates from Almeria were studied using RAPD. Eleven primers that gave 79 reproducible RAPD markers were used.
Results and conclusions
Sclerotia and mycelia of B. cinerea survived inside and outside the greenhouse until next crop in 1995 and 1997, although survival was higher outside. Fourteen out of 22 isolates survived after 3 ;days at 40°C and all of them survived 7 ;days at 30 or 35°C . All isolates were pathogenic when inoculated in tomato leaves.
Crops were surveyed and neither apothecia nor sclerotia were observed on infected plants. Soil inside the greenhouses and cull piles outside the greenhouses were also analysed and no inocula were recovered. Mycelia was found in decaying leaves in ornamental vineyards close to the greenhouses and also found in debris of infected plants that remained hanging inside the greenhouses.
Trapping spores showed that initial inoculum in grey mould epidemics stem from outside, as conidia. The disease was observed in plants only when colonies appeared in plates inside the greenhouse.
The genetic similarity among B.&ndsp;cinerea isolates was high. The presence of groups of isolates from different greenhouses with a high genetic similarity indicated the existence of an intense exchange of conidia among the greenhouses.
1. Delcan J, Melgarejo P, 1996. XIth International Botrytis Symposium: Book of Abstracts, p.18.