An Outbreak of Gray Mold Caused by Botrytis cinerea on Kenaf (Hibiscus cannabinus L.)

Abstract

A severe outbreak of gray mold on kenaf (Hibiscus cannabinus L.) was observed on kenafgrown in the research field of Gyeongsangnam-do Agricultural Research and Extension Services,Jinju, Korea in 2014. Gray mold appeared on young plants as gray-brown velvety moldcovering stems and leaves. Infections that girdled the stem caused wilting above the infectedarea and developed a canker. The casual fungus formed grayish brown colonies on potatodextrose agar. The conidia were one celled, mostly ellipsoid or ovoid in shape, colorless or palebrown in color, and 6–18 × 4–10 μm in size. The conidiophores were 15–32 μm in length. These measurements and taxonomic characteristics were most similar to those of Botrytis. DNAsequencing and phylogenetic analysis of the complete internal transcribed spacer rRNA generegion confirmed that the fungal isolates were indeed Borytis cinerea. Koch's postulates weresupported by pathogenicity tests conducted on healthy plants. On the basis of mycologicalcharacteristics and pathogenicity test on host plants, the fungus was identified as Botrytiscinerea. To the best of our knowledge, this is the first report of a gray mold caused by B. cinerea on kenaf in Korea.