Journal of Plant Pathology Archive

Abstract:

Marigold (Tagetes erecta) is one of the commercial ornamental flowers commonly grown in Bangladesh. In January 2011, rotten flowers of marigold covered with fluffy white mycelia were found in Rangpur, Bangladesh. Symptoms began from petals and subsequently expanded to the whole flower and the lower part of the plant. Dark brown lesions with necrotic tissues appeared on the infected leaves and stems. Seriously infected plants showed flower dropping and branch wilting. A fungus showing hyaline and septate mycelia was isolated from the infected tissue using potato dextrose agar. The fungus formed round to irregular-shaped sclerotia. Apothecia development from sclerotia were also observed on moist sand. The partial sequence (531 bp, GenBank accession No. AB937102) of the internal transcribed spacer region of rDNA was determined by the method described in Rahman et al. (2015). The result showed a 100% identity with those of Sclerotinia sclerotiorum, which is known as a pathogen to various plants (Purdy, 1979). Pathogenicity of the isolate to marigold was examined by detached leave and flower assays using the mycelial block. After incubation at 20°C with 90% relative humidity in 12 h light/12 h dark conditions, all inoculated leaves and flowers were rotten, while no symptom developed on the controls. The fungus was re-isolated from the symptomatic tissues and Koch’s postulates were confirmed. In Bangladesh, the fungus is becoming an emerging threat to various hosts (e.g. Rahman et al., 2015). To our best knowledge, this is the first report of S. sclerotiorum infection on marigold in the country.