A polyphasic characterization of small-spored Alternaria from Argentina

DA CRUZ CABRAL, L.; RODRIGUEIRO, MARCELA; STENGLEIN, S.; NIELSEN, K.F.; PATRIARCA, A.

Freising

Workshop; 2016 ICFM Workshop; 2016

Accurate identification of fungal contaminants in food is critical in the development of prevention strategies at pre- andpost-harvest stages. Even though Alternariais frequently isolated from Argentinean crops, little is known on thevariability and differentiation of its populations in this country. The objective of this study was the characterization througha polyphasic approach of 45 small-spored Alternariaspp. obtained from edible parts from tomato fruits, pepper fruits, wheat andblueberries, involving morphological, metabolomic and molecular analyses. The isolates were grown on Potato Carrot Agar at 25ºC under an alternating light cycle (8 h light, 16 h darkness)for 7 days. Morphological classification was achieved according to Simmons(2007). Metabolite profiling was carried out in DRYES (14 days, 25ºC) by micro-extractionwith ethyl acetate-1% formic acid. Detection was performed by HPLC-MS (ESI-TOF).Amplification and sequencing of a portion of the endopolygalacturonase gene(endoPG) and subsequent Bayesian analysis using a Kimura 80 model were carriedout.Morphologically, isolates were classified as A. tenuissima sp.-grp. (29/45), A. arborescens sp.-grp. (11/45), and A. alternata sp.-grp. (2/45). The 3remaining strains exhibited intermediate characteristics among the threementioned groups and were referred to as Alternariasp. By secondary metabolites analysis, no compound representative of morphologicalgroups could be detected; all isolates showed overlapping profiles. Bayesian analysisfrom endoPG gene yielded two clades, both containing isolates belonging to thethree species-groups and the four substrates with short branch length,indicating low number of substitutions per site. Even though morphological differences wereobserved, and most of the isolates could be assigned to a species-group basedon them, the whole set of analysis suggested that they were strongly related. Nocorrelation between morphospecies and phylogenetic or metabolomic studies couldbe established. These results are in agreement with recent Alternaria organization systems, which incorporate these 3 species-groupsin a single section within the genus (Alternariasect. Alternaria).