• The Plant Pathology Journal
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• v.18 no.6
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• pp.301-307
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• 2002

Graft transmission and cytopathological studies of a severe pear disease, pear black necrotic leafspot（PBNLS), were carried out to determine the causal agent of the disease. No evidence was found that a fungal or bacterial pathogen could be the causal agent of the disease. Attempts to transmit the agent by sap-inoculation to other plants including herbaceous hosts failed. How-ever, the pathogen was readily graft-transmitted from symptomatic diseased pears to healthy pears. Graft transmission of the pathogen was also demonstrated by using an indicator plant, PS-95, developed in the laboratory through various grafting methods. Ultrastructural study of the disease revealed the consistent presence of flexuous rod-shaped virus-like particles (VLP) in the symptomatic leaves of both Niitaka cultivar and indicator pear, PS-95. The particles, approximately 12 nm in diameter with undetermined length, occurred in the cytoplasm of mesophyll parenchyma cells. Cells with VLPs also contained fibril-containing vesicles, which are common in cells infected with plant viruses with ssRNA genome. The vesicles were formed at the tonoplast. Based on the symptomatology, the presence of fibril-containing vesicles, and graft-transmissibility, it is believed that the VLPs that occurred on symptomatic leaves of black necrotic leafspot of pear are viral in nature, possibly those of a capillovirus.

• Journal of Plant Biotechnology
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• v.49 no.3
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• pp.222-229
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• 2022

Apples are the most grown fruit crops in the fruit industry of Korea. However, virus or viroid infection such as apple mosaic virus (ApMV), apple stem grooving capillovirus (ASGV), apple stem pitting virus (ASPV), apple chlorotic leaf spot virus (ACLSV), apple scar skin viroid (ASSVd) causes fruit yield reduction and poor fruit quality. Therefore, in this study, we examined to established an efficient virus-free system to eliminate the most infected ASGV virus in domestic apple orchard. We investigated that the shoot growth rate and the virus removal rate in ASGV infected potted apples that were treated with heat treatment in a growth chamber (constant temperature/humidity device) maintained at 36℃, 38℃ and 40℃ for 4 weeks. Here we found that the shoot growth rate was the highest in the heat treatment group (36℃) and the virus was removed in the middle and top of the shoot but not in the bottom. The virus was did not removed in the 38℃ and 40℃ heat treatment group in all section of shoots, and the heat treatment group (40℃) died after 4 weeks of heat treatment without growth of shoots. We performed in vivo shoot-tip grafting using the shoot-tip of potted apple heat-treated at 36 ℃, and we also investigated the viability and virus removal rate, which showed 94% viability and 20% virus removal rate. Collectively, our results suggest that it would be possible to produce the virus-free apple plants through heat treatment and shoot-tip grafting.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.122-123
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• 2003

Apple stem grooving virus (ASGV) belongs to Capillovirus and infects pome fruits. Transmission mode of ASGV is known by grafting and mechanical inoculation into susceptible hosts, not by any other natural vectors. But we have observed the spread of ASGV in the field without mechanical inoculation or grafting. Transmission seems to be occurred from tree-to-tree and tree-to-susceptible herbaceous plants along but not across ditches in the field. In order to ascertain this possibility, various fungi were isolated and cultured from ASGV-infected plants and 69 isolates were characterized. By means of RNA dot-blot hybridization and PCR analysis, 3 isolates were sorted out for further studies. The isolates were identified to Tataromyces sp. and belonged to Phenicillium by morphological characteristics and molecular markers. As an experimental host, 10 kidney beans (Phaseolus vulgaris) were screened and Kyunggi-5 was selected for virus amplification and symptom development. Kyunggj-5 infected by fungi which seemed to carry ASGV showed the typical disease symptoms and viral coat protein genes were detected from all tested plants. To confirm the Koch's rule, fungi cultured from inoculation origins of kidney bean were grown on PDA media and re-inoculated to hosts. The fungi isolated from inoculation origins induced the typical disease symptoms on hosts. However virus free fungi did not induce any symptom on the experimental hosts. This bioassay showed that these typical symptoms were caused by virus, not fungi.