OCCURENCE OF FUSARIUM EQUISETI AS A CONTAMINANT OF DIPLOTAXIS TENUIFOLIA SEEDS
G. Gilardi, I. Pintore, M.L. Gullino, A. Garibaldi
Fusarium equiseti, the causal agent of leaf spot of both wild [Diplotaxis tenuifolia (L.) DC] and cultivated [Eruca vesicaria (L.) Cav.] rocket, is a new pathogen on these crops, which has increasingly been found on several commercial farms in Italy. In order to investigate the possible transmission of this pathogen through infested seeds, both wild and cultivated rocket seeds, from eight commercially available seed lots, have been collected from four farms suffering from severe field losses. F. equiseti was identified through morphological observations and molecular analysis based on the elongation factor 1 alpha gene (EF-1α). Four out of six seed lot samples of wild rocket were found to be contaminated, while the pathogen was not isolated from the two tested seed lots of E. vesicaria. The highest level of detected infestation was 5 out of 800 non-disinfected Diplotaxis sp. seeds. F. equiseti was not isolated from disinfected seeds. Nine of eleven isolates of F. equiseti obtained from seeds were pathogenic on wild rocket. This work demonstrates that F. equiseti can be transmitted by Diplotaxis tenuifolia seeds. The external nature of seed contamination of Diplotaxis sp. by F. equiseti has been proved. More extensive essays on seed lots of cultivated rocket are needed in order to have a better understanding of the seed transmissibility of the pathogen on such a host.