Penetration and infection processes in japanese cedar twig blight caused byStromatinia cryptomeriae |
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| Authors: | Takanori Kubono Norio Sahashi Shin’ichiro Ito |
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| Institution: | (1) Tohoku Research Center, Forestry and Forest Products Research Institute, 020-0123 Morioka, Japan;(2) Kyushu Research Center, Forestry and Forest Products Research Institute, 860-0862 Kurokami, Japan;(3) Laboratory of Forest Pathology and Mycology, Department of Sustainable Resource Sciences, Faculty of Bioresources, Mie University, 514-8507 Tsu, Japan |
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| Abstract: | The diversity of host invasion mechanisms of the causal pathogen of Japanese cedar twig blight (Stromatinia cryptomeriae) was elucidated through detailed investigations of the disease cycle. Scanning electron microscopy (SEM) showed that ascospores
began to germinate, and invade male strobilus tissue, within 24 h after arriving on the strobili. This involved direct penetration
of the cuticle, and examination by SEM showed that cuticle degeneration had occurred around the point of penetration. A mucilage-like-substance
was also observed around the tips of the germ tubes. Meanwhile field studies showed that incipient mycelial mat emerged from
the bases of male strobilus in early June, and ceased growing onto the surface of the twig at the beginning of July. Macroscopically,
the mycelial mat began to shed in mid-July, and disappeared completely during the summer season by the end of August. Immediately
after the mat disappeared the first necrotic symptoms became evident on the twigs. This suggested strongly that these mats
were involved in lesion formation. Observations of the mat’s behavior on the surface of twigs with light and differential
interference microscopy, and SEM, showed thatS. cryptomeriae had two modes of invasion,i.e. stomatal and cuticular invasion. Hyphae from the mat were able to enter twig tissues through the stomata. Additionally, mycelial
mat infected host tissue directly by hyphal penetration of the cuticle at the axes of cedar twigs. The mat was able to grow
along the twig surface, then hyphae forming mat entered the host tissue and caused necrotic lesions. This paper describes
the mechanisms of infection on both a strobilus and twig utilized by the pathogen of Japanese cedar twig blight. |
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| Keywords: | Cryptomeria japonica infection process Japanese cedar twig blight Stromatinia cryptomeriae |
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