Occurrence of Target Spot on Rosemary Caused by Corynespora cassiicola in Korea

Abstract

The purpose of this experiment was to investigate the development of new spot disease on the leaf and stem of rosemary (Rosmarinus officinalis) in commercial greenhouses at Jeonju and Namwon in Korea. Incidence of target spot on rosemary was higher at the end of the rainy season with high humidity. Those symptoms were black ring spots (3−5 mm in diameter) and withering on green leaves and stems. Conidiophores and conidia were formed on the infected tissue in moist chamber and conidia were shown as the cylindrical and oval types in chain, ranged from 55 to 275 µm in length, and 7 to 14 µm in width. Conidia with eight to ten pseudosepta were formed on the conidiapore. The optimum growth temperature of isolates was 30 o C on the PDA medium under the dark condition. In the pathogenesis test, the target spot and withering symptoms were appeared on the leaves and stems 3 days after inoculation showing similar symptoms compared to those of in nature. The same fungus was re-isolated from infected lesion, indicating that Corynespora cassiicola caused leaf target spot and twig blight on rosemary. The rDNA ITS nucleotide sequences of the pure cultured isolate from the diseased area on rosemary showed 100% similarity to the sequences of C. cassiicola available in the GenBank database (JQ595296, JQ595297, FJ852715 and AY238606). Therefore, we report that the target spot of leaves and stems in rosemary was caused by C. cassiicola.

The calcium cyanamide and polyethylene blocks the secondary transmission and infection of vegetable leaf diseases

“…C. cassiicola can infect more than 530 plant species, including cucumber, tomato, and cowpea, resulting in huge economic losses in more than 70 countries ( Dixon et al., 2009 ). C. cassiicola mainly infects healthy leaves through air transmission and seed carriers ( Lee et al., 1990a ; Goulart and Utiamada, 2020 ). The pathogen could remain alive on plant residue into soil about several months, which caused the pathogen aggravated year after year ( Erick and Scott, 2007 ; Mi et al., 2010 ).…”