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

September 2000 , Volume 90 , Number  9
Pages  973 - 976

R. D. Johnson , L. Johnson , K. Kohmoto , H. Otani , C. R. Lane , and M. Kodama

First, second, third, fourth, and sixth authors: Laboratory of Plant Pathology, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan; fifth author: Central Science Laboratory, Sand Hutton, York, YO41 1LZ, UK

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Accepted for publication 18 May 2000.

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.

Additional keywords: host-selective toxin, molecular diagnostics.

© 2000 The American Phytopathological Society