• The Plant Pathology Journal
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• 제17권4호
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• pp.216-221
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• 2001

Dieback of pine branches or twigs with brown needles occurs most commonly on Pinus species after severe winter in Korea. In this study, Cenangium ferruginosum was isolated from infected stems, branches, and twigs of Pinus koraiensis (C1), P. densiflora (C2), and P. thunbergii (C3). Morphological and cultural characteristics of the isolates were than compared. There were no significant differences in the morphological characteristics of conidia and ascospores produced by the three isolates. However, cultural differences were observed among the isolates. Optimum temperatures for mycelial growth of C1, C2, and C3 were 15, 20, and $20^{\circ}$, respectively. C1 produced a few conidia and no ascospores, while C2 and C3 produced abundant ascospores and conidia. While optimum temperatures for mycelial growth ranged from 15 to $20^{\circ}$, mycelial growth was also relatively good at lower temperatures of 5-$10^{\circ}$. Conidiomata and conidia were produced on MSA (malt extract soya peptone agar) after 25-30 days of incubation in the dark at $15^{\circ}$. Apothecia were produced by altering culture condition from 15 to $20^{\circ}$, and incubating for 35-60 more days. Optimum temperature for ascospore and conidium germination was $20^{\circ}$. RAPD analysis revealed that there was high similarity of 0.78 between C2 and C3, and low similarity of 0.31 between C2 or C3 and C1.

• Mycobiology
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• 제44권4호
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• pp.319-324
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• 2016

Dieback in strawberry (Seolhyang cultivar) was first observed during the nursery season (June to September) in the Nonsan area of Korea in the years 2012 and 2013. Initial disease symptoms included dieback on runners, as well as black rot on roots, followed by wilting and eventually blackened, necrotic discoloration in the crowns of daughter plants. A fungus isolated from the diseased roots, runners, and crowns is close to Lasiodiplodia theobromae based on morphological characteristics. Analysis of a combined dataset assembled from sequences of the internal transcribed spacer and translation elongation factor 1- alpha genes grouped nine fungal isolates with the type strain of L. theobromae. The isolates showed strong pathogenicity on strawberry cultivars Kumhyang, Seolhyang, and Akihimae, fulfilling Koch's postulates. Based on these results, the pathogen responsible for dieback on strawberry plants in Korea was identified as L. theobromae.

• Mycobiology
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• 제42권4호
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• pp.391-396
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• 2014

In the past two decades, European ash trees (Fraxinus spp.) have been severely damaged due to ash dieback disease, which is caused by the fungal species Hymenoscyphus fraxineus (Chalara fraxinea in the anamorphic stage). Recent molecular phylogenetic and population genetic studies have suggested that this fungus has been introduced from Asia to Europe. During a fungal survey in Korea, H. fraxineus-like apothecia were collected from fallen leaves, rachises, and petioles of Korean ash and Manchurian ash trees. The morphological and ecological traits of these materials are described with the internal transcribed spacer rDNA sequence comparison of H. fraxineus strains collected from Korea, China and Japan.

• The Plant Pathology Journal
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• 제16권3호
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• pp.137-141
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• 2000

A causal fungus of turfgrass blight was isolated from the infected leaves of zoysiagrass (Zoysia japonica Steud.) and identified as Nigrospora sphaerica (Sacc.) Mason by using a light misroscope. Its conidia are large (14-20 ${\mu}{\textrm}{m}$ diameter), shiny, black, aseptate, and smooth-walled spheres. The fungus caused typical blighting symptoms on the two turfgrass plants of bermudagrass (Cynodon dactylon (L.) Pers.) and bentgrass (Agrostis palustris Huds.). The fungus was found to produce a phytotoxic subtance to be associated with the pathogenic mechanism. A phytotoxin was isolated from the liquid cultures of N. sphaerica by repeated silica gel column chromatography and its structure was determined to be 5, 6-dihydro-5-hydroxy-6-propenyl-2H-pyr-2-one (T-3 compound). It was not a host-specific toxin showing phytotoxic effects to various plants inclusing turfgrasses in the leaf-wounding assay, the whole plant test, and the cellular leakage test. The compound caused leaf tip dieback symptoms in turfgrass plants similar to those caused by the pathogen. Thus, T-3 compound is thought to be involved in the development of Nigrospora blight.

• 식물병연구
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• 제18권2호
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• pp.101-108
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• 2012

소나무재선충에 자연 감염된 소나무와 잣나무로부터 소나무재선충을 분리하여 수종 간 분리율과 수종 내 부위별 밀도 등을 비교하고, 분리한 선충을 소나무 묘목에 접종하여 묘목 내에서의 이동을 알고자 하였다. 2006년, 소나무재선충에 감염되어 말라죽었거나 죽어가고 있는 소나무와 잣나무로부터 소나무재선충을 분리한 결과, 소나무재선충은 두 수종 모두에서 높은 밀도로 분리되어 수종 간에 차이를 보이지 않았다. 또한, 각 수종의 변재부 위에서만 분리되었으며, 분리한 조직을 채취한 줄기의 높이에 따른 분리율에는 차이가 없었다. 즉, 말라죽은 나무의 주간은 모든 조직이 소나무재선충에 감염되어 있었다. 소나무 묘목에의 접종실험을 통하여 감염목 내 이동을 조사한 결과, 감염초기에 소나무 조직 내로 침입한 소나무재선충은 증식에 앞서 감염목 내에서 빠르게 이동하여 퍼지기 시작하였고, 그 이후에 왕성한 증식활동을 하였으며, 이 시기가 바로 소나무 시들음병의 외부병징이 나타나는 시기가 일치함을 알 수 있었다. 소나무재선충의 이동경로를 조사하기 위해 접종한 소나무 줄기횡단면을 현미경으로 관찰하고, 또 높이별로 선충을 분리하여 조직 내 선충의 분포를 관찰한 결과, 줄기의 피층에 있는 수지도를 통해 접종부위로부터 다른 부위로 빠르게 이동을 하고, 시간이 경과하면서 조직 내에서 증식한 소나무재선충은 피층의 수지도뿐만 아니라 목질부수지도나 가도관까지 분포하여 감염목내 전 부위에 걸쳐 고루 분포하였다. 그러나 수조직에서는 분리할 수 없었다. 소나무재선충 분리밀도가 높았던 묘목은 뿌리의 발달이 불량하거나, 목질부 변색균에 감염된 것들이었으며, 비교적 튼튼한 외양을 한 묘목에서는 선충의 분리밀도가 낮았다.