Alternaria petroselini pathogen of parsley in Serbia

Abstract

After its first detection in 2005, Alternaria petroselini, the causal agent of black leaf spot, has become one of the most important pathogens of parsley (Petroselinum crispum (Mill.) Nym.) in Serbia. During almost a decade, isolates of A. petroselini originating from parsley leaves, seed and infested soil were collected and identified on the bases of morphological, pathogenic and molecular features. All morphological features were consistent with those described previously, including dark brown colonies on potato dextrose agar (PDA) and subsurface microsclerotia production, and the presence of pigmented, broadly ellipsoidal, singly produced feodyctiosporic conidia. Pathogenicity and host range studies using spray inoculation of spore suspensions, revealed that isolates were pathogenic for parsley, parsnip, celery and coriander, weakly pathogenic for carrot, fennel and anise, and not pathogenic for onion, cabbage, pepper, tomato, and cucumber. Molecular detection utilizing polymerase chain reaction (PCR) and A. radicina specific primers failed to demonstrate a difference between A. petroselini and A. radicina, amplifying isolates belonging to both species. For further confirmation of Serbian A. petroselini isolates, sequencing of selected genomic fragments including ITS and mitochondrial small subunit (mtSSU) rDNA and major allergen Alt a1, b-tubulin, and translation elongation factor-1 alpha (EF1a) protein coding genes was performed. All obtained sequences were deposited in GenBank and BLAST search for the closest matching revealed several A. petroselini isolates from GenBank to share 99-100% nucleotide identity. Parsley is traditionally grown herb and vegetable plant in Serbia and A. petroselini causes considerable damage every year and occasionally very severe yield losses, resulting in significant economic impact, especially in parsley leaf production. Further investigation of the epidemiology and population structure of A. petroselini is needed in order to establish efficient control measures.