Corm and root rot of Colocasia esculenta caused by Ovatisporangium vexans and Rhizoctonia solani

摘要

Ovatisporangium vexans (de Bary) Uzuhashi, Tojo & Kakis. and Rhizoctonia solani Kiihn were isolated from the decayed parts of roots and corms of wilted taro (Colocasia esculenta (L.) Schott.) plants. Although both pathogens were identified according to morphological and pathogenicity characteristics, O. vexans identification was further confirmed based on the internal transcribed spacer (ITS) sequences of 18S ribosomal RNA (rRNA) and 28S rRNA genes using the ITS6 and ITS4 primers. Early symptoms on leaves appeared as pale yellow color, partial rolling of leaf margins and withering of seedlings. Rotting or decay started at the collar region and it spread to roots and corms. In severe cases, the collar region broke off and the seedling collapsed. Inoculating these isolates separately into mature taro plants and corms resulted in symptoms similar to root and corm rots observed on naturally infected plants. Both disease agents were re-isolated from the inoculated tissues. Since symptoms caused by co- inoculation of O. vexans with R. solani together were more severe, combination of two pathogens induced the greatest plant mortality. This is the first report of corm and root rot disease caused by O. vexans and R. solani complex on taro plants in Turkey. This is also the first record of O. vexans in Turkey.