Leaf Spot of Cotton Rose Caused by Corynespora cassiicola in Korea

ABSTRACT

A leaf spot of cotton rose (Hibiscus mutabilis) occurred severely in the flower beds of cotton rose around Uiryeong-gun, Gyeongnam Province in Korea. The causal fungus was identified as Corynespora cassiicola on the basis of cultural and morphological characteristics of the fungus. The fungus grew well on potato dextrose agar and the colony color was gray to brown. Conidia were solitary or catenate, obclavate to cylindrical in shape, and pale olivaceous brown or brown in color. They had 420 pseudosepta, and measured 35.2~173.6 x 8.8~19.9 microm. Conidia germinated as a bipolar type. Conidiophores were pale to mid brown in color, and measured 74.2~275.6 x 3.8~10.8 microm. Optimal temperature for mycelial growth was 30degrees C. The fungal isolate grown on PDA showed strong pathogenicity to cotton rose plant. This is the first report on the corynespora leaf spot of cotton rose (Hibiscus mutabilis) caused by Corynespora cassiicola in Korea.