THE ENDOPOLYGALACTURONASE GENE BCPG1 IS REQUIRED FOR FULL VIRULENCE OF BOTRYTIS-CINEREA

Botrytis cinerea, a fungus that causes diseases in over 200 plant spec ies, secretes a number of endopolygalacturonases that have been sugges ted to be involved in pathogenesis. However, so far the corresponding genes have not been isolated from this fungus. We cloned Bcpg1, encodi ng endopolygalacturonase, with the pgaII gene from Aspergillus niger a s a heterologous probe. The Bcpg1 gene is expressed to similar levels in liquid cultures of B. cinerea containing either 1% polygalacturonic acid or 1% sucrose, and is expressed during infection of tomato leave s. The Bcpg1 gene was eliminated by partial gene replacement, and the resulting mutants were tested for virulence on tomato leaves and fruit s, as well as on apple fruits. Although the mutants were still pathoge nic and displayed similar primary infections when compared with contro l strains, a significant decrease in secondary infection, i.e., growth of the lesion beyond the inoculation spot, was observed on all three host tissues. These results indicate that the Bcpg1 gene is required f or full virulence.