Angular Lesions Research Articles

First laboratory confirmation of Xylophilus ampelinus in Slovenia*

Bacterial blight of grapevine is caused by a slow‐growing bacterium Xylophilus ampelinus. It has been suspected to occur in Slovenia on the basis of visual observation of characteristic symptoms in the 1960s. In the present study, symptoms were recorded in an infected vineyard during three consecutive years (2002/2004). Samples from this vineyard were tested by nested‐PCR and isolation of bacteria on media was attempted. In the first year, angular lesions on leaves were highly expressed and an isolate morphologically similar to X. ampelinus was obtained from one sample. It was purified and identified as X. ampelinus using biochemical and nutritional tests, fatty acid analysis, immuno‐fluorescence, nested PCR and partial sequencing of the 16S rRNA gene. The 16S rDNA sequence showed 99–100% homology to known sequences of X. ampelinus strains, including the type strain. Pathogenicity of the isolate was confirmed in tissue‐cultured and potted grapevine plants. In the following two years, symptoms of bacterial blight were only faintly expressed. Using isolation on media and nested‐PCR, 23 and 17 extracts prepared from 10 and 8 grapevines, respectively, were analysed. In 2003, no positive sample was found, but X. ampelinus was again isolated and identified by colony morphology and nested‐PCR in 2004.

First Report of a Leaf Spot Caused by Cladosporium oxysporum on Greenhouse Tomato.

In a commercial greenhouse in upstate New York, dark brown, angular lesions were first observed in April on lower, older leaves of 4-month-old tomato plants (Lycopersicon esculentum Mill. 'Jumbo'). Chlorosis frequently developed around the lesions. Removal of the infected leaves reduced the rate of epidemic development. However, by July, lesions were present throughout the plant canopy, up to 2 m. The irregularly shaped lesions varied in size from 1 to 5 mm, frequently with tan-colored centers initially. Conidia developed in the center of the lesions, primarily on the outer, or adaxial side of the leaf, but were infrequent on the abax-ial surface. This contrasts with Cladosporium leaf mold caused by Fulvia fulva, in which the conidia develop as a velvety brown patch in lesions on the abaxial, or underside of the leaf, accompanied by chlorosis on the upper side of the leaf (1). The conidia ranged in shape from oval or li-moniform (5 to 6 μm in diameter) to cylindrical (5 to 6 μm wide, 7 to 20 μm long). The fungus was identified as Cladosporium oxysporum Berk. & M. A. Curtis (3) by C. J. K. Wang and J. M. McKemy of the State University of New York College of Environmental Science and Forestry in Syracuse, NY. Koch's postulates were fulfilled with a tuft of mycelium and conidia grown on potato dextrose agar as inoculum on fully expanded leaves of 5-week-old tomato plants, cv. Jumbo. Two weeks later, characteristic sporulating lesions developed on inoculated plants, about 1 cm from the inoculation site. Within 3 weeks, in the research greenhouse, the disease spread to healthy tomato plants in the vicinity, confirming the highly infectious nature observed in the commercial greenhouse. The fungus was reisolated from inoculated leaves and also from the adjacent naturally infected plants. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and also a storage disease of ripe tomato fruit (4). To the best of our knowledge this is the first report of C. oxysporum causing disease on tomato foliage.

Treatment of interproximal angular defects by guided tissue regeneration: 1 year follow‐up

SUMMARY The periodontal regeneration of interproximal bone defects of the posterior teeth produced by guided tissue regeneration (GTR), with expanded Polytetrafluoroethylene barrier membranes and conventional therapy, was clinically evaluated in 20 intrabony periodontal defects in 10 patients. The material included the presence of at least two proximal angular lesions for the same patient, probing pocket depth ≥ 6 mm, bone defect depth ≥ 3 mm, and 2‐wall defects with crestal involvement relative to the tooth circumference ranging from 90 to 270°. Healing was clinically evaluated by surgical re‐entry of GTR‐treated sites (10 sites) and debridement only sites (10 sites) 1 year after initial surgery following a strict plaque control regimen. A significant correlation was observed between probing depth reduction, attachment gain and defect depth (test sites); there was increased bone fill in GTR‐treated lesions of 2.95 ± 1.3 mm corresponding to a 69.4% improvement compared to control sites, and 1–3 ± 1.0 mm corresponding to a 32% improvement (P < 0.0039). The results demonstrated that bone regeneration is highly reliable, as compared to conventional therapy, in cases of severe periodontal bone loss from posterior teeth provided that the principles of GTR are applied.

Nematode Angular Leaf Spot of Dry Bean in Wyoming

A new foliar disease of dry bean, nematode angular leaf spot (NALS), is caused by Aphelenchoides ritzemabosi. The disease is typified by numerous dark, angular lesions on leaves and occasionally a superficial necrosis on the upper surface of the petiole. Diagnosis of NALS is based on the presence of foliar symptoms and recovery of nematodes from symptomatic tissue. Infested fields were infrequent in a field survey of 7,175 ha in Wyoming conducted during a 3-year period. The field survey represented 17% of the crop harvested during those years. Therefore, it is unlikely that NALS will cause economic yield loss unless conditions for nematode survival and foliar parasitism are unusually favorable. The nematode is also known to parasitize alfalfa foliage in Wyoming and other western states. Infested dry bean fields found during the survey had a recent history of alfalfa production. Therefore, alfalfa and dry bean crop rotation provides a potential mechanism for nematode survival. Parasitic nematodes persisted in air-dried bean leaf tissue for at least 27 months, which suggests that persistence of NALS inoculum in crop debris is likely to occur in the field.

Phenotypic characterization of mononuclear cells and Class II antigen expression in angular cheilitis infected by Candida albicans or Staphylococcus aureus

In the present study we characterized the phenotypes of infiltrating mononuclear cells in angular cheilitis lesions to further explore the pathogenesis of this disorder. Frozen sections from lesions infected by Candida albicans and/or Staphylococcus aureus were subjected to immunohistochemical analysis utilizing monoclonal antibodies directed to subsets of T-lymphocytes, B-lymphocytes, and macrophages. In addition, the expression of Class II antigens (HLA-DP, -DQ, -DR), the interleukin 2- and transferrin-receptors was studied on resident and infiltrating cells. An intense infiltration of T-lymphocytes was accompanied by expression of Class II antigens on the epidermal keratinocytes in lesion infected by Candida albicans. The Staphylococcus aureus infected lesions displayed a diffuse infiltration of T-lymphocytes but virtually no expression of Class II antigen by epidermal keratinocytes. These observations suggest that the cell-mediated arm of the immune system is involved in the inflammatory reaction of lesions infected by Candida albicans. In addition, the present study confirms that epidermal expression of Class II antigens is closely related to the type and magnitude of the infiltrating T-lymphocyte. Finally, these findings indicate that the type of inflammatory reaction in angular cheilitis is primarily dependent on the isolated microorganism, although the clinical pictures of the disorder are virtually identical.

Resistance reactions of Cucumis melo to inoculation with Pseudoperonospora cubensis

SUMMARYReactions of several cultivars and breeding lines of melons to artificial inoculation at the seedling stage with a local isolate of Pseudoperonospora cubensis were compared under growth chamber and field conditions. Four different reactions were distinguishable: highly susceptible, susceptible, partially resistant and resistant. The differences in the reactions were more clear‐cut under growth chamber conditions. Selection for resistance could be carried out at the seedling stage using sporangia production and lesion size, shape, colour and number as criteria. Under growth chamber conditions, plants of resistant lines had minimal sporangia production and circular or angular lesions 1–2 cm in diameter which became necrotic within 5 days after inoculation.

Histology of the muco-cutaneous junction at the corner of the human mouth

Tissue was examined from the angle of the mouth of 30 post-mortem subjects, ranging in age from neonates to 80 years. In infants the commissure consisted histologically of three zones; skin, vermilion border and mucosa. In adults a fourth or intermediate zone was observed between the vermilion border and mucosa. The epithelium of the four zones showed a number of differentiating features and, with age, the vermilion border increased in length and thickness, whilst oral mucosa became significantly thinner. The number of mast cells decreased with age and this was most marked in the oral mucosa. Elastic fibres were most common in skin, but collagen and reticulin showed little difference in distribution. Oxytalan fibres were present in all zones at all ages. However, collastin was found only in skin and vermilion border and these are the zones most likely to be exposed to sunlight. These changes may be significant in the pathogenesis of angular lesions of the lips.

Vertical dimension as it relates to the etiology of angular cheilosis

It is disputed that “overclosure” is a common cause of angular cheilosis in the wearers of complete dentures, especially when the upper basal seat tissues are inflamed. This contention is based on the effect on angular lesions when 97 patients left dentures out of the mouth for two weeks. This permitted maximum “over-closure” to occur; and in the majority of these patients, the lesions resolved. In the absence of pre-extraction records, there seems to be no accurate routine method of assessing the occlusal vertical dimension that is based on sound scientific principles.

STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS: II. BACTERIAL LEAF BLIGHT DISEASE OF CASTOR (RICINUS COMMUNIS L.)

The bacterial disease of castor in the Sudan has been reinvestigated. Typically the disease symptoms are brown or black, round or angular lesions on leaves; occasionally the thin succulent branches are attacked, but not the vascular tissue.The bacterium responsible for the disease was previously thought to be Pseudomonas solanacearum E.F.Sm. but comparative studies show that the Sudan species differs in pathogenicity and physiology from P. solanacearum. It closely resembles Xanthomonas ricinicola (Elliott) Dowson (=Bacterium ricini Yoshi and Takimoto) in characters, host range and pathogenic effects. In culture on solid media the growth of X. ricinicola is typically yellow, while that of the Sudan species is dirty white; but this difference is not considered sufficient to justify the establishment of a new species.The author proposes the specific name ricini originally adopted by Archibald (1927) and Yoshi & Takimoto (1928), for the species of Xanthomonas causing the leaf blight disease of castor, and considers that the causal organism in the Sudan is an atypical strain of this species.