Journal of Plant Pathology Archive

Abstract:

Leaf spots were observed on Veronica spicata subsp. incana, V. spicata subsp. spicata and V. spuria plants growing at at Budapest-Soroksár (Hungary) during field surveys conducted in 2010 and 2012 with a frequency of 90-100% and a severity of 29.7-58.2%. Leaf spots were roundish and dark brown, with a thin purplish margin. From these spots a fungus was isolated on malt extract agar, characterized by conidiophores forming synnemata rising from the abaxial leaf surface. The fungus was identified as Phacellium veronicae (Pass.) U. Braun. Conidia were hyaline, aseptate or occasionally with one septum, ovoid to cylindrical and measured 5.1-11.9 × 1.7-2.5 μm (8.5 × 2.3 μm in average). Synnemata were 106.3-487.5 μm in height (301.7 μm in average). Pathogenicity was assessed by placing small agar plugs excised from fungal colonies on excised Veronica officinalis leaves kept in moist chamber at 24°C with a 12 h photoperiod. Half of the leaves were pricked with a needle prior to inoculation. Non inoculated leaves served as controls. After 8 days, necrotic spots 8-11 mm in diameter and 13-20 mm in diameter developed around the inoculation point on unwounded leaves and wounded leaves, respectively. DNA was extracted from the mycelium of two fungal isolates and subjected to PCR using ITS5/ITS4 primers. The obtained sequences (GenBank accession Nos HQ690097 and JQ920427) showed 97.7 to 97.9% similarity with a Chinese sequence of Phacellium veronicae (HE995799) (Bai et al., 2013). In Europe the occurrence of this fungus on Veronica spp. was reported from Denmark, Germany, Italy, Romania (Braun, 1998) and Russia (Mel’nik et al., 2007). To our knowledge this is the first report of P.veronicae-induced leaf spots on speedwell in Hungary.