Archivio Journal of Plant Pathology

Abstract:

During summer 2014, leaf spots were observed on a number 6- to 8- month-old plants of autumn sage (Salvia greggii) in a private garden near Biella (northern Italy). Brown small irregular lesions were present on the leaves of plants grown in the shadow with high relative humidity which, at the final stage, were almost completely defoliated. A fungus consistently isolated on potato dextrose agar (PDA), was characterized by a gray mycelium producing hyaline, cylindrical, aseptate and thin walled conidia (7.5-19.3 x 2.8-6.0, average 13.9 x 4.4 μm) in acervuli which, based on these traits, was identified as a Colletotrichum sp. (Bailey and Jeger, 1992). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4, and custom-sequenced. BLAST analysis (Altschul et al., 1997) of the 510 bp amplicon (GenBank accession No. KP792748) showed 100% similarity with Colletotrichum coccodes (AM422215.1). Leaves of three healthy 10-month- old potted plants of S. greggii were inoculated by spraying a conidial suspension of 1x105 CFU/ml. Control plants were sprayed with sterile distilled water. Plants were covered with plastic bags and kept in a greenhouse at 18 to 25°C. Symptoms similar to those observed on naturally infected sage appeared on all inoculated plants 14 days post inoculation while controls remained healthy. C. coccodes was consistently reisolated only from inoculated plants. This is to our knowledge the first report of C. coccodes on S. greggii worldwide. The disease is currently limited to the area where it was first observed. However, C. coccodes could become a significant problem due to its wide host range that includes also other member of lamiaceae such as peppermint.