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Rapid Change in the Genetic Diversity of Botrytis cinerea Populations After the Introduction of Strains in a Tomato Glasshouse

February 2009 , Volume 99 , Number  2
Pages  185 - 193

V. Decognet, M. Bardin, Y. Trottin-Caudal, and P. C. Nicot

First, second, and fourth authors: INRA, UR0407, Plant Pathology Unit, Domaine St. Maurice, F-84140 Montfavet, France; and third author: Centre Technique Interprofessionnel des Fruits et Légumes, Centre de Balandran, BP. 32, F-30127 Bellegarde, France.

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Accepted for publication 1 October 2008.

In tomato glasshouses, the population structure of airborne inoculum of Botrytis cinerea depends on the production of endogenous inoculum on diseased plants as well as on incoming exogenous inoculum. Both types of inocula may contribute differently to the development of epidemics. Two strains of B. cinerea were introduced in each of four separate compartments of an experimental tomato glasshouse. We monitored their impact on disease development and on the genetic diversity of B. cinerea populations using microsatellite markers. The naturally occurring airborne inoculum of B. cinerea displayed a high level of genetic diversity and was rapidly displaced in the glasshouse, as isolates with microsatellite profiles identical to the introduced strains amounted to 66% of the inoculum sampled from the air 14 days after inoculation and 91% of those collected from stem lesions 60 days after inoculation. This suggested an important role of secondary inoculum in disease development, which is compatible with the hypothesis of a polycyclic development of gray mold epidemics in tomato glasshouses. In controlled-environment tests on tomatoes, a wide range of aggressiveness levels was observed, both for isolates sampled from the air and from lesions on plants. Hypotheses are proposed to explain the negligible impact of naturally incoming isolates on the epidemics observed inside the four glasshouse compartments.

Additional keywords:clonal population, fitness, Solanum lycopersicum, spora flux, sustainable control.

© 2009 The American Phytopathological Society