Characterization of Alternaria Species Associated with Heart Rot of Pomegranate Fruit

Abstract

This study was aimed at identifying <i>Alternaria</i> species associated with heart rot disease of pomegranate fruit in southern Italy and characterizing their mycotoxigenic profile. A total of 42 <i>Alternaria</i> isolates were characterized. They were obtained from pomegranate fruits with symptoms of heart rot sampled in Apulia and Sicily and grouped into six distinct morphotypes based on macro- and microscopic features. According to multigene phylogenetic analysis, including internal transcribed spacer (ITS), translation elongation factor 1-α (EF-1α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a SCAR marker (OPA10-2), 38 isolates of morphotypes 1 to 5 were identified as <i>Alternaria alternata</i>, while isolates of morphotype 6, all from Sicily, clustered within the <i>Alternaria arborescens</i> species complex. In particular, isolates of morphotype 1, the most numerous, clustered with the ex-type isolate of <i>A. alternata</i>, proving to belong to <i>A</i>. <i>alternata</i>. No difference in pathogenicity on pomegranate fruits was found between isolates of <i>A. alternata</i> and <i>A. arborescens</i> and among <i>A. alternata</i> isolates of different morphotypes. The toxigenic profile of isolates varied greatly: in vitro, all 42 isolates produced tenuazonic acid and most of them other mycotoxins, including alternariol, alternariol monomethyl ether, altenuene and tentoxin.