Archivio Journal of Plant Pathology

Abstract:

In October 2014, symptoms were observed in Euphorbia mammillaris var. variegata (Euphorbiaceae family) plants in a nursery of Vallecrosia (Imperia province, Northern Italy), consisting of wilting and rotting of the stems, which turned brown starting from the collar, and death of the affected plants. A fungus consistently isolated from infected tissues produced chlamydospores, microconidia and macroconidia on carnation leaf agar (CLA). Macroconidia were slightly falcate, septate, with a foot-shaped basal cell, a short apical cell, and measured 31.1-48.5×2.6-4.1 (mean: 39.6×3.2) μm. These morphometric characteristics are typical of Fusarium oxysporum (Leslie and Summerell, 2006). DNA from a sin- gle-spore culture was used to amplify the elongation factor 1 alpha gene (EF1α) using primers EF1/EF2 (O’Donnell et al., 1998). A 682 bp product was obtained whose sequence was deposited in GenBank under the accession No. KT183485. BLASTn analysis of this amplicon showed 100% homol- ogy with the sequence of F. oxysporum DQ837689. Three healthy plants of E. mammillaris var. variegata inoculated as described by Talgø and Stensvand (2013) died about 14 days post the inoculation, while controls remained symptomless. The same fungus was reisolated only from inoculated plants. This is the first report of F. oxysporum on E. mammillaris var. variegata in Italy and elsewhere. The forma specialis of this F. oxysporum should be investigated as well as the susceptibility of succulent plants most cultivated in Italy to avoid the spread of this pathogen.