Morphocultural variants of Septoria tritici isolates.

This is a morphocultural study under in vitro and in vivo condition on some Septoria tritici variants mainly originated from isolates collected from cultivars bearing Bobwhite 'S' and Kavkaz germplasm. The objective was to show the variability in cultural and morphobiometrical characters of atypical isolates (variants) derived from these germplasms and discuss the relationship with the pathogen's adaptative process. The isolates were grown on potato dextrosa agar and studies with the optical and scanning electron microscope were performed. The thallus behaviour and the vegetative structures were described. It was confirmed that these atypical structures belong the S. tritici thallus. Under in vivo condition the isolates developed typical leaf blotch lesions with normal pycnidia. These contained cylindrical cells or pycnidiospores smaller than spores of the "wild type". Possible reasons for the origin of these variants of S. tritici are considered.

[Bacterial leaf blight affecting Syngonium podophyllum in Argentina]. / Tizón bacteriano de Syngonium podophyllum en la Argentina.

Bacterial leaf blight of Syngonium podophyllum caused by Xanthomonas campestris pv. syngonii is recorded for the first time in Argentina. The first symptom of the disease was an interveinal watersoaking of leaves, the tissues became chlorotic and finally necrotic over areas of about 4 cm. The identification of the causal microorganism was based on disease symptoms, morphological, physiological and biochemical characteristics and pathogenicity test.

Tizón bacteriano de Syngonium podophyllum en la Argentina / [Bacterial leaf blight affecting Syngonium podophyllum in Argentina]

Bacterial leaf blight of Syngonium podophyllum caused by Xanthomonas campestris pv. syngonii is recorded for the first time in Argentina. The first symptom of the disease was an interveinal watersoaking of leaves, the tissues became chlorotic and finally necrotic over areas of about 4 cm. The identification of the causal microorganism was based on disease symptoms, morphological, physiological and biochemical characteristics and pathogenicity test.

Tizón bacteriano de Syngonium podophyllum en la Argentina. / [Bacterial leaf blight affecting Syngonium podophyllum in Argentina]

Bacterial leaf blight of Syngonium podophyllum caused by Xanthomonas campestris pv. syngonii is recorded for the first time in Argentina. The first symptom of the disease was an interveinal watersoaking of leaves, the tissues became chlorotic and finally necrotic over areas of about 4 cm. The identification of the causal microorganism was based on disease symptoms, morphological, physiological and biochemical characteristics and pathogenicity test.

[Relation between the production of deoxynivalenol and zearalenone and the mycelial growth of Fusarium graminearum on solid natural substrates]. / Relación entre la producción de deoxinivalenol y zearalenona y el crecimiento micelial de Fusarium graminearum en sustratos naturales sólidos.

A toxicogenic strain of Fusarium graminearum which produces DON and ZEA was cultivated on natural solid substrates (wheat, polished rice and hulled rice) under different environmental conditions. The production of both toxins and mycelium growth (in terms of glucosamine) were evaluated to establish the relation between the production of DON and ZEA and the different mycelium growth on the substrates mentioned above. Polished rice was the substrate on which most production of both toxins was obtained. Comparing the three substrates studied, the highest quantities of DON were obtained at a temperature of 27 degrees C during incubation period, being indifferent to the presence of light except in the case of hulled rice. Whereas for ZEA the best conditions in wheat and polished rice were medium temperatures (17 degrees-21 degrees C respectively) and darkness. While in hulled rice the ideal conditions for the production of both toxins were temperature of 27 degrees C and the presence of light. Concerning the mycelium growth, this was very scarce when cultivated in hulled rice, increasing in polished rice and being largest in wheat. The increase or reduction of the mycelium growth in the different substrates was not proportional to the increase or decrease of the production of both toxins. Therefore, production of DON and ZEA could be subjected to the nature of the substrate and environmental conditions, more than the rate of development of Fusarium graminearum in cereal grains.

[Loquat canker: a new disease for Argentina]. / Cancrosis del níspero: una nueva enfermedad para la Argentina.

A stem canker disease caused by Pseudomonas syringae pv. eriobotryae (Takimoto) Young, Dye y Wilkie on loquat (Eriobotrya Japonica [Thumb] Lindl) was recorded for the first time in Argentina. Symptoms of the disease appeared as dry stem cankers which in advanced stages surrounded the stems. Similar cankers were noticeable on leaves midribs. Seven bacterial strains were isolated from diseased loquats and their identification was based on disease symptoms, pathogenicity and cultural and biochemical characteristics. All strains were levan positive and gave a hypersensitive reaction on tobacco leaves. Neither arginine dehydrolase nor oxidase was detected in any of the strains which produced a diffusible green pigment on King B which fluoresced under UV light and a distinct diffusible brown pigment on King B, SPA and Tween 80 media within 5-7 days of incubation. Lipolysis of Tween 80 was also recorded. The symptoms observed in the field and obtained by experimental inoculations were similar to those induced by Pseudomonas syringae pv. eriobotryae in the original description of the disease.

[Antagonism in vitro among phytopathogenic and saprobic fungi from horticultural soils]. / Antagonismo in vitro entre hongos fitopatógenos y saprobios de suelos hortícolas.

Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.

Antagonismo in vitro entre hongos fitopatógenos y saprobios de suelos hortícolas / [Antagonism in vitro among phytopathogenic and saprobic fungi from horticultural soils]

Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.

Antagonismo in vitro entre hongos fitopatógenos y saprobios de suelos hortícolas. / [Antagonism in vitro among phytopathogenic and saprobic fungi from horticultural soils]

Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.

Cancrosis del níspero: una nueva enfermedad para la Argentina. / [Loquat canker: a new disease for Argentina]

A stem canker disease caused by Pseudomonas syringae pv. eriobotryae (Takimoto) Young, Dye y Wilkie on loquat (Eriobotrya Japonica [Thumb] Lindl) was recorded for the first time in Argentina. Symptoms of the disease appeared as dry stem cankers which in advanced stages surrounded the stems. Similar cankers were noticeable on leaves midribs. Seven bacterial strains were isolated from diseased loquats and their identification was based on disease symptoms, pathogenicity and cultural and biochemical characteristics. All strains were levan positive and gave a hypersensitive reaction on tobacco leaves. Neither arginine dehydrolase nor oxidase was detected in any of the strains which produced a diffusible green pigment on King B which fluoresced under UV light and a distinct diffusible brown pigment on King B, SPA and Tween 80 media within 5-7 days of incubation. Lipolysis of Tween 80 was also recorded. The symptoms observed in the field and obtained by experimental inoculations were similar to those induced by Pseudomonas syringae pv. eriobotryae in the original description of the disease.

Observaciones sobre la histopatología de la viruela del apio / Histopathology of the smallpox of celery

Con el objeto de determinar la vía de penetración y posterior desenvolvimento de Septoria apiicola Speg, en hojas de apio, se desarrolló una técnica histopatológica de aclaramiento y tinción para poder efectuar esas observaciones. El micelio resultante de la germinación de las esporas penetra a través de los estomas y a partir de ellos se desenvuelve un micelio grueso, intercelular que forma picnidios con desarrollo sinfógeno. De ese micelio interno surgen a través de los estomas de 1 a 4 hifas gruesas y largas. Se supone que este es un medio más de diseminación que posee el hongo. Este mismo mecanismo se observó en S. Iycopersici Spet. y S. musiva Pk. por lo que se sospecha sea propio del género Septoria. Estudios adicionales confirmarán o no esta hipótesis

Observaciones sobre la histopatología de la viruela del apio / Histopathology of the smallpox of celery

Con el objeto de determinar la vía de penetración y posterior desenvolvimento de Septoria apiicola Speg, en hojas de apio, se desarrolló una técnica histopatológica de aclaramiento y tinción para poder efectuar esas observaciones. El micelio resultante de la germinación de las esporas penetra a través de los estomas y a partir de ellos se desenvuelve un micelio grueso, intercelular que forma picnidios con desarrollo sinfógeno. De ese micelio interno surgen a través de los estomas de 1 a 4 hifas gruesas y largas. Se supone que este es un medio más de diseminación que posee el hongo. Este mismo mecanismo se observó en S. Iycopersici Spet. y S. musiva Pk. por lo que se sospecha sea propio del género Septoria. Estudios adicionales confirmarán o no esta hipótesis (AU)

[Sensitivity of the skin of the rabbit to extracts of a culture of Fusarium poae (Peck) Wollenweber]. / Sensibilidad de la piel de conejo a extractos de cultivo de Fusarium poae (Peck) Wollenweber.

Toxic metabolites from some Fusarium poae (Peck) Wollenweber strains can produced alimentary toxic aleukia in man. In order to establish the toxicity of a F. poae strain isolated in our country, a skin test was performed in a depilated area of the flank of non-pigmented skin and white hair rabbits. The toxicity of culture extracts, measured according to the intensity of the lesions, was evidenced by the cellular degenerative processes induced. Rats fed with the same fungus strain cultured on sterile corn developed internal haemorrhages.

Sensibilidad de la piel de conejo a extractos de cultivo de Fusarium poae (Peck) Wollenweber. / Rabbit skin sensitivity to culture extracts of Fusarium poae (Peck) Wollenweber

Ciertas cepas de Fusarium poae (Peck) Wollen. son productoras de metabolitos que ocasionan la aleuquia toxica alimenticia (A.T.A.) en seres humanos, como sucedio en Rusia en 1942. Para establecer el poder toxico de una cepa de Fusarium poae aislada de trigo, se efectuo una prueba biologica sobre piel de conejo. Con ese fin se utilizaron conejos de pelo y piel blancos a los que se rasuro una superficie del flanco donde se probaron posteriormente los extractos. El poder de toxicidad fue medido en base a una escala de acuerdo al grado de lesion producido. Se demostro que la cepa era realmente toxica dado que provoco avanzados procesos degenerativos celulares. Se suministraron oralmente cultivos del mismo hongo en maiz esteril a ratas albinas las que sufrieron hemorragias internas

Sensibilidad de la piel de conejo a extractos de cultivo de Fusarium poae (Peck) Wollenweber. / Rabbit skin sensitivity to culture extracts of Fusarium poae (Peck) Wollenweber

Ciertas cepas de Fusarium poae (Peck) Wollen. son productoras de metabolitos que ocasionan la aleuquia toxica alimenticia (A.T.A.) en seres humanos, como sucedio en Rusia en 1942. Para establecer el poder toxico de una cepa de Fusarium poae aislada de trigo, se efectuo una prueba biologica sobre piel de conejo. Con ese fin se utilizaron conejos de pelo y piel blancos a los que se rasuro una superficie del flanco donde se probaron posteriormente los extractos. El poder de toxicidad fue medido en base a una escala de acuerdo al grado de lesion producido. Se demostro que la cepa era realmente toxica dado que provoco avanzados procesos degenerativos celulares. Se suministraron oralmente cultivos del mismo hongo en maiz esteril a ratas albinas las que sufrieron hemorragias internas

Sensibilidad de la piel de conejo a extractos de cultivo de Fusarium poae (Peck) Wollenweber. / [Sensitivity of the skin of the rabbit to extracts of a culture of Fusarium poae (Peck) Wollenweber]

Toxic metabolites from some Fusarium poae (Peck) Wollenweber strains can produced alimentary toxic aleukia in man. In order to establish the toxicity of a F. poae strain isolated in our country, a skin test was performed in a depilated area of the flank of non-pigmented skin and white hair rabbits. The toxicity of culture extracts, measured according to the intensity of the lesions, was evidenced by the cellular degenerative processes induced. Rats fed with the same fungus strain cultured on sterile corn developed internal haemorrhages.