Mating Type and Vegetative Incompatibility in Filamentous Ascomycetes

Abstract

In filamentous ascomycetes, mating type and vegetative incompatibility con­ fer selflnonself recognition in the sexual and vegetative reproductive phases, respectively. In the first section of this review, we discuss selflnonself recognition in the sexual cycle, with specific emphasis on the ascomycetes, Neurospora crassa, Podospora anserina, and Cochliobolus heterostrophus. The recent cloning and sequencing of the mating-type genes from these organisms has allowed the clarification of molecular aspects regarding the regulation of the sexual cycle. From a practical standpoint, understanding the regulation of mating type can be important to the plant pathologist. The sexual cycle can generate genetic diversity that can adversely affect resistance breeding or chemical control strategies. Sexual reproduction results in asco­ spores that can function as overwintering structures or infective propagules and can be an important component of the disease cycle. The second section of this review covers vegetative incompatibility and its role in self/nonself recognition during asexual reproduction. The genetics of Neurospora crassa, Aspergillus nidulans, and Podospora anserina, and the