EPPO Global Database

EPPO Reporting Service no. 04 - 2001 Num. article: 2001/076

PCR method to detect Alternaria alternata apple pathotype (A. mali)

The form-genus Alternaria includes both pathogenic and non-pathogenic species. Within A. alternata, 7 pathogens which could not be distinguished from saprophytic A. alternata on the basis of conidial morphology, but which presented a particular pathogenicity, have been designated as pathotypes (however, it must be noted that this classification is subject to debate). These pathotypes have a distinct and limited host range and are characterized by the production of host-specific toxins. Recent work has indicated that Alternaria pathogens which produce host-specific toxins are pathogenic variants within the species Alternaria alternata. Therefore, Alternaria blotch of apple is now considered to be caused by Alternaria alternata apple pathotype, although it was previously described as the distinct virulent form of Alternaria mali (EPPO A1 quarantine pest). Recently, a gene playing a crucial role in the biosynthesis of the apple-specific toxin (AM-toxin) was cloned and characterized. It was also shown that this gene is only present in isolates of A. alternata apple pathotype. Using primers targeted for this gene, a PCR method has been developed to identify specifically isolates of A. alternata apple pathotype which produce the AM-toxin.


Johnson, R.D.; Johnson, L.; Kohmoto, K.; Otani, H.; Lane, C.R.; Kodama, M. (2000) A polymerase chain reaction-based method to specifically detect Alternaria alternata apple pathotype (A. mali), the causal agent of Alternaria blotch of apple.
Phytopathology, 90(9), 973-976.