Physiological and Molecular Plant Pathology (1998) 52, 213–221 Article No. : pp970143 Association of Pestalotia malicola with the plant cuticle : visualization of the pathogen and detection of cutinase and non-specific esterase J. A. S*, S. F. P†, H. K, R. J. H and R. L. N‡  Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA,  Laboratory of Plant Pathology, Faculty of Bioresources, Mie University, Tsu 514-8507, Japan, and  Central Research and Development, DuPont Co. Wilmington, DE 19880-0402, USA (Accepted for publication November 1997) The fungus Pestalotia malicola attacks fruits of Chinese quince (Chaenomeles sinensis) in Japan. Scanning electron microscopy (SEM) in combination with micromanipulation as well as cryo SEM demonstrated that the fungus was growing on, within, and beneath the fruit cuticle. The ability of the pathogen to grow in association with the cuticle suggested that the fungus produces cutinase(s) andor non-specific esterase(s). Enzyme assays revealed that the fungus produced an enzyme, or enzymes, with activities characteristic of a cutinase and a non-specific esterase when cultured on cucumber cutin as the sole carbon source. The same enzyme activities were also demonstrated to be constitutively present in the extracellular matrix that surrounds conidia in conidiomata.  1998 Academic Press INTRODUCTION Species of the fungus Pestalotia are common pathogens of a broad variety of plants found in temperate and tropical regions of the world [5 ]. Some species appear to grow primarily as saprophytes [7, 20 ], whereas others are more aggressive and cause severe leaf blights, especially in trees [1 ]. Although there are few detailed investigations on the infection processes of these fungi, it is apparent that they often exhibit latent infections and are more aggressive as pathogens in tissue that has been wounded [5 ]. Another characteristic is that species typically grow on or within the plant cuticle as well as subcuticularly [5, 7, 17 ]. Because of our interest in the involvement of cutinase and non-specific esterases in the fungal infection process [4, 14, 15, 16, 18, 19 ], the present investigation was carried out to determine whether Pestalotia, because of its growth in association with the plant cuticle, produces these enzymes. We demonstrate that the fungus Pestalotia malicola does grow within the fruit cuticle and produces both cutinase and non-specific esterase activities in io and in itro. *Present address, Departamento de Bioquı  mica, Universidade Federal do Parana  , Curitiba, PR, Brasil. †Present address, Departamento de Fitopatologia, ESALQ, Universidade de Sa  o Paulo, Piracicaba, SP, Brasil. ‡To whom correspondence should be addressed. 0885–57659804021309 $30.000  1998 Academic Press