• The Plant Pathology Journal
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• v.17 no.5
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• pp.295-299
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• 2001

The relative density of phytoplasmas in witches'broom (WB)-infected jujube trees was investigated using compatitive polymerase chain reaction (PCR). During dormant and defoliating seasons, the densities of phytoplasmas were about the same in roots and twigs. In early growing season, the density showed the highest rates in roots, then in twigs and in petioles. however, the density was highest in petioles and the lowest in roots during actively growing season. Throughout the year, root samples did not show any serious fluctuation compared with that of t2wigs and petioles. Density was lowest during actively growing season in root samples. In contrast, petiole sample densities varied to a great extent depending on the season, very high during actively growing season, but very low during the early growing season, In twig samples, the densities were very high and almost the same in both defoliating and dormant seasons. Among the parts of the trees, phytoplsma density was the most stable in root samples throughout the year. The highest densities of phytoplasmas were about the same in all tree parts. These results suggest that the phytoplasmas may overwinter not only in roots but also in twigs, and that multiplication rate of phytoplsma becomes very high right after the early growing season.

• Research in Plant Disease
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• v.17 no.3
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• pp.265-271
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• 2011

Seven phytoplasma diseases have been occurred on floricultural crops in Korea : Ph-ch1 and Ph-ch2 of chrysanthemum, Ph-lily of lily, petunia flat stem-Korean (PFS-K) of petunia, poinsettia branch inducing- Korean (PoiBI-K) of poinsettia, statis witches' broom-Korean (SWB-K) of statis and azalea witches broom (AWB). Classification of the seven phytoplasmal diseases based on 16S ribosomal RNA (rRNA) sequences showed that floricultural crop phytoplasma disease were widespread in order of aster yellow (AY), stolbur and X-disease in Korea. In phenotypic characters, the fasciation was occurred in both monocotyledon plant of lily and dicotyledon plants of petunia and poinsettia. Besides, the fascination was occurred in Ph-lily of stolbur, petunia PFS-K of AY and PoiBI-K of X-disease. This result indicated that phytoplasma classification based on 16S rRNA and symptoms are not consistently related. The comparison of 16S rRNA sequence of the seven floricultural crop phytoplasma with five tree phytoplasmal diseases of jujube witches' broom, paulownia witches' broom, wild jujube witches' broom, mulberry dwarf, golden rain phytoplasma occurred in Korea showed as high as 88.5-99.9% homology. Among them, especially mulberry dwarf showed the highest homology with the seven floricultural crop phytoplasms. Based on this result, floricultural crop phytoplasmas were assumed to be transmitted by insect vectors from tree phytoplasmas in Korea.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.382-385
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• 1998

Molecular identification and genetic relationships between a phytoplasma associated with chestnut little leaf (CLL) and phytoplasma isolates of other trees in Korea were amplified by polymerase chain reaction (PCR). These 16S rDNA sequences amplified from the various phytoplasmas were used in DNA heteroduplex mobility assays (HMA). In DNA HMA combined with PCR, the mobility shift was observed for a heteroduoplex formed in combined with CLL and jujube witches broom, but not for those formed in combined with CLL and each of sumac witches broom, paulownia witches broom, and mulberry dwarf. HMA combined with PCR has been shown to be a very useful method for detection and differentiation of phytoplasmas.

• Journal of Korean Society of Forest Science
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• v.48 no.1
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• pp.29-39
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• 1980

This study was initiated to find out the possible insect vector and other means of transmission of jujube witches'-broom disease. 1. Eight species of leafhoppers were found to feed on both healthy and diseased jujube trees. Among these, rhombic marked leafhoppers (Hishimonus sellatus Uhler) were most abundant throughout the growing season of jujube trees in all localities surveyed. H. sellatus was far more abundant on diseased trees than healthy ones. 2. Jujube witches'-broom mycoplasma(JWM) was transmitted to jujube seedlings by Hishimonus sellatus. Jujube seedlings inoculated with H. sellatus which had been fed for 14-21 days on diseased jujube plants, developed smaller, chlorotic leaves 40-60 days after inoculation. Electron microscopy of midveins and petioles of the infected jujube seedlings revealed the presence of numerous mycoplasmalike organisms in phloem tissues. 3. Jujube witches'-broom mycoplasma was also transmitted to Vinca rosea plants by H. sellatus. Infected Vinca rosea plants developed vein clearing and marginal chlorosis of upper leaves 25-38 days after inoculation and followed by stunting and ultimate wilting and death of plant. Electron microscopy of petioles and midveins of infected Vinca rosea plant revealed the presence of numerous mycoplasmalike organisms in phloem tissues. 4. H. sellatus survived more than 30 days on jujube, Vinca rosea, carrot, celery, eggplant, hop, Calystegia japonica, Humulus japonicus, Astragalus sinicus, white clover, red clover, and radino clover. Many second generation nymphs of H. sellatus were also abserved on these plants but clovers. 5. Jujube seeds collected from witches'-broom diseased jujube trees yielded healthy seedlings.

• Research in Plant Disease
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• v.26 no.1
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• pp.19-28
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• 2020

Jujube witches' broom (JWB) disease is a high-risk plant disease that occurred on and devastated jujube orchards throughout South Korea in the 1950s. Recently, as the jujube cultivation area has been significantly increased nationwide, we investigated the disease in jujube orchards in the Boeun region to obtain basic information for proactively evaluating the risk of JWB outbreaks from 2017 to 2019. A field trial was conducted to evaluate the effect of the trunk injection of Sungbocycline (a. i. oxytetracycline calcium alkyl trimethyl ammonium 17%, OTC). The incidence of JWB disease was very low in Boeun, but it was gradually increased mainly in the area and on the farms where it had occurred previously. The trunk injection with OTC was most effective in the early stages of growth. However, even though the trees were treated with OTC, disease symptoms appeared in other healthy branches in severely affected trees. When the tree was first injected with OTC in June, the control efficacy of second injection was higher one month after the first injection than five months. These results suggest that early diagnosis based on various symptoms and early control based on them can be very effective in preventing JWB disease in advance and increasing control efficacy.

• Journal of Korean Society of Forest Science
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• v.66 no.1
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• pp.79-81
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• 1984

Protein profiles of healthy and witches' broom (mycoplasma) infected jujube plants (Zizyphus jujuba) were investigated by 2-30% linear gradient polyacrylamide gel electrophoresis. Distinct differences in band patterns between healthy and infected samples were observed. Gels from samples of healthy leaves showed a characteristic protein band in the 50kd-range, which was not detected in infected leaves. Band with 25kd was more distinct in the infected leaves, whereas band with 198kd was more apparent in the healthy leaves. Healthy-looking leaves in the infected samples demonstrated the characteristic band of 50kd with less intensity showing intermediate pattern between healthy leaves and infected leaves. In contrast with leaf samples, gels from infected stem samples showed a characteristic band in the 335kd-range which was absent in healthy stem samples.

• Korean Journal Plant Pathology
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• v.1 no.2
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• pp.101-108
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• 1985

Histopathological changes in the witches'-broom mycoplasma (MLO) infected jujube trees after trunk injection of oxytetracycline HCl (OTC) solution were investigated by using light microscope, fluorescence microscope and electron microscope. In contrast to the healthy leaves, adaxial and abaxial bundle sheath extensions in the major veins of diseased leaves were highly developed, but mesophyll cells were very small, loose and necrosed. In the diseased leaves, excessive phloem was formed, xylem differentiation was supressed and polyphenols were accumulated. Jujube trees treated with 500ml of 2000ppm solution of OTC showed complete remission of witches'-broom symptoms above the injection site, but cells in the sheath extention were hypertrophied and sieve tube necrosis occurred in the secondary phloem of major veins. MLO-specific fluorescence was not observed in the samples of diseased jujube trees treated with OTC, while those from non-treated infectedstress distinctly showed a moderate amount of MLO-specific fluorescence. In the observation under the electron microscope, sieve element of diseased tissues and its associated companion cells were found to have collapsed. Parenchymas cells contained many large starch filled plastids and most samples of diseased and OTC-treated tissues showed an abnormal accumulation of starch compared to the healthy controls. Mycoplasma-like organisms were observed only within mature sieve elements in diseased tissues, but never in OTC-treated tissues.

• Korean journal of applied entomology
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• v.23 no.4 s.61
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• pp.215-220
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• 1984

Mulberry dwarf, paulownia witches' broom, jujube witches' broom, and sumach witches' broom are known to be associated with mycoplamalike organisms(MLO) in Korea. Simple microscopic detection of MLO infection in these plants was attempted. Periwinkle plant was also tested. Application of $0.2\%\;and\;0.4\%$ solution of Dienes' stain gave diagnoatic value for MLO-induced diseases of periwinkle and mulberry. Among the various plant parts examined, young herbaceous stem just below the apical part gave the best result. Density of staining reaction was proportional to disease severity. Longitudial sections were superior to transverse sections in confirming MLO infection by staining. Light source without blue filter was useful for increasing the color contrast between sieve tube and xylem vessel and for eliminating misinterpretation. Paulownia, jujube, and sumach samples gave no clear difference in staining reaction between healthy and diseased sections even when various modifications of Dienes' staining procedure were tried.

• Korean journal of applied entomology
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• v.4
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• pp.7-10
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• 1965

In an experiment to evaluate the various aspects of symptom of witches' broom of jujube tree with two different kinds of scions, taken from diseased plant and stem- grafted upon sound stocks-one cut before wintering(stored in cellar), the other after wintering, it was observed that the disease rate of those cut before wintering(Nov.) was $\98\%$ whereas those cut after wintering(March) showed much lower rate, $3\%$ initially and gradually increased up to $39\%$. In another experiment of diseased bud grafted into healthy seedling, the finding made in the following year was that 14 stocks(only one of which salt union by callusing) were infected out of the given 23- in the initial stage only 4, yet gradually increased to the number of 14. The shoots from the ground portion of the diseased stock were in general more quickly subjected to the disease than the others. Under natural condition, the diseased trees develop at first seemingly the same leaves as healthy ones; it is not until the branches and loaves grow to a considerable degree that the symptom appears. Once appearing, tile disease grows and the symptom continues to appear as late as in Sept. and early Oct., causing tile plant to develop the extraordinary branches and leaves of extremely reduced size, the typical symptom of witches' broom. Such phenomenon can be observed in the experiments of the foregoing paragraphs. And the suckers and roots of diseased plant are bound to be infected, it was found out with no exception. Viewing from the results of the above experiments and observation, it is believed that the low temperature during winter causes the virus in the above-ground portion of diseased plant to diminish or inactivated, and subsequently the virus in the roots moves up or multiply in the sprouting season.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.191-196
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• 2012

Periwinkle seedlings (Cantharanthus roseus) were inoculated with jujube witches'- broom (JWB) phytoplasma via grafting to analyze the migration of JWB phytoplasmas within the host plant. The phytoplasmas were detected using nested polymerase chain reaction (PCR) and fluorescence microscopy. Fluorescence microscopy was a simple and easy method of detecting phytoplasmas; however, it was not sufficiently sensitive to detect very low phytoplasma concentrations. Therefore, the migration of JWB phytoplasma was investigated through PCR. The first migration of JWB phytoplasma from an infected tissue to healthy tissues occurred late. After grafting, the phytoplasmas moved from the inoculated twig (or scion) to the main stem, which took 28 days. Afterward, the phytoplasma migrated faster and took less than 4 days to spread into the roots from the main stem. All twigs were then successively colonized by the JWB phytoplasmas from the bottom to the top. JWB phytoplasma was detected via nested PCR in all parts of the periwinkle seedling 82 days after inoculation. Based on these results, the inoculated JWB phytoplasma appeared to migrate downward to the roots along the main stem during the early stages, and then continued to move upward, colonizing twigs along the way until they reached the apex.