A Polymerase Chain Reaction-Based Method to Specifically Detect<i>Alternaria alternata</i>Apple Pathotype (<i>A. mali</i>), the Causal Agent of Alternaria Blotch of Apple

Abstract

ABSTRACT Alternaria alternata apple pathotype (previously A. mali) causes Alternaria blotch on susceptible apple cultivars through the production of a host-specific toxin, AM-toxin. Identification of some Alternaria species, especially those that produce host-specific toxins, has been extremely difficult due to a high level of variability which extends even to nonpathogenic isolates. We have recently cloned and characterized a gene (AMT) that plays a crucial role in AM-toxin biosynthesis and demonstrated that it is only present in isolates of A. alternata apple pathotype. Using primers designed for the AMT gene, we developed a polymerase chainreaction-based method to specifically detect AM-toxin producing isolates of A. alternata apple pathotype.