Soft Rot on Citrus unshiu Caused by Rhizopus oryzae in Korea

Kwon, Jin Hyeuk; Kim, Jin Woo; Hyun, Jae Wook; Lee, Yong Hwan; Shim, Hong Sik

Research in Plant Disease 2011;17(1):78-81.
Published online April 30, 2011.

Rhizopus oryzae에 의한 감귤 무름병

권진혁, 김진우, 현재욱, 이용환, 심홍식

Soft Rot on Citrus unshiu Caused by Rhizopus oryzae in Korea

Jin Hyeuk Kwon, Jin Woo Kim, Jae Wook Hyun, Yong Hwan Lee, Hong Sik Shim

Abstract

Soft rot caused by Rhizopus oryzae occurred on unshiu orange (Citrus unshiu Marc.) sampled from commercial markets in Jinju, Korea, 2010. The first symptom of soft rot on orange is a water-soaked appearance of the affected tissue. The infected parts later disintegrated into a mushy mass of disorganized cells followed by rapid softening of the diseased tissue. The lesion on orange was rapidly softened and rotted, then became brown or dark brown. Optimum temperature for mycelial growth of the causal fungus on potato dextrose agar was 30℃ and growth was still apparent at 37℃. Sporangiophores were 6~20 μm in diameter. Sporangia were globose and 40~200 μm in size. The color of sporangia was brownish-grey to blackish-grey at maturity. Sporangiospores were sub-globose, brownish- black streaked and 4~10 μm in size. Columella were globose to sub-globose and 85~120 μm in size. On the basis of mycological characteristics, pathogenicity test, and the ITS sequence analysis, the causal fungus was identified as Rhizopus oryzae. To our knowledge, this is the first report of soft rot caused by R. oryzae on unshiu orange in Korea.

Key Words: Citrus unshiu, Rhizopus oryzae, Soft rot, Unshiu orange