En raíces de plantas adultas de tomate se observó una lesión castaña de aspecto húmedo, que se extendía 2-4 cm por encima del suelo. Las plantas atacadas se marchitaron y murieron. El objetivo del trabajo fue aislar e identificar al organismo causal de esta sintomatología. Se usaron medios de cultivos generales y selectivos. A las 24 horas desarrollaron colonias con micelio blanco algodonoso. Se evaluó la morfología de la colonia y la producción, morfología y dimensiones de estructuras reproductivas. El rDNA del micelio de un aislamiento fue extraído de cultivos puros con 7-10 días de crecimiento en medios agarizados. La región ITS se amplificó usando primers ITS4 e ITS5, se secuenció y comparó en banco de genes del servidor BLAST- NCBI para verificar su similitud con las secuencias tipo u holotipo disponibles. Al microscopio se observó micelio cenocítico, esporangios esfericos-globulados y oosporas apleroticas característicos del género Pythium. Se efectuaron pruebas de patogenicidad con resultados positivos reaislándose un microorganismo de características idénticas. La caracterización lograda por las técnicas tradicionales, los estudios moleculares y el resultado de las pruebas de patogenicidad permiten concluir que Pythium aphanidermatum es el causante de la Podredumbre basal de plantas adultas de Tomate.
Production of arugula (Eruca sativa) has increased greatly in Argentina. Since 2002, particularly during the fall, a foliar disease has affected commercial crops in Capilla del Señor (northeast of Buenos Aires Province, Argentina). The disease appeared in foci, spreading throughout the whole production field or greenhouse. Severely affected crops were plowed under. Diseased leaves were chlorotic and had white sori that emerged through the abaxial epidermis. Sori corresponded to the white rust agent, Albugo candida (Pers.) Kunze (1). Sporangiophores were hyaline and clavate, and sporangia were globose and hyaline with a mean diameter of 16.2 μm (14.2 to 19.2 μm). Pathogenicity tests were performed by spraying a suspension of 106 zoospores/ml or 5 × 104 sporangia/ml on four healthy 30-day-old arugula plants. Inoculum was prepared by scrapping sporangia from infected leaves. Sporangia were used directly or incubated in sterile distilled water (SDW) for 14 h at 5°C to induce zoospore formation (2). Four additional healthy plants were sprayed with SDW to serve as controls. Plants were kept in plastic bags for 48 h and maintained in the greenhouse thereafter. White rust symptoms, similar to those observed on the original plants from the field, were observed on inoculated plants 10 days after inoculation. To our knowledge, this is the fist report of A. candida on arugula in Argentina. References: (1) K. Mukerji. No. 458 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1975. (2) H. Scheck and S. Koike. Plant Dis. 83:877, 1999.
During the fall of 2005, arugula (Eruca sativa Mill.) plants grown in experimental field plots in Buenos Aires, Argentina presented V-shaped necrotic lesions on leaf margins and blackened veins with broad yellow halos, followed by leaf necrosis. At flowering, 96% of the plants were affected with 27% of the leaves with symptoms. Yellow, round, mucoid, convex, bacterial colonies were isolated from several leaves on yeast dextrose chalk agar. Two strains were further studied. Xanthomonas campestris pv. campestris Xcc8004 was used as a control. Strains were gram negative, rod shaped, strictly aerobic, catalase-positive, oxidase and urease-negative, hydrolyzed starch, gelatine and aesculin, and did not reduce nitrate (2). Pathogenicity was tested by spraying 10 3-week-old arugula plants with either a bacterial suspension (107 CFU/ml) or sterile water. Plants were placed in plastic bags for 72 h after inoculation. All inoculated plants showed necrotic lesions enlarging from the margin of the leaves 7 days after inoculation. No lesions were observed on control plants. On the basis of biochemical characterization (2) and genomic fingerprints generated by BOX-PCR (1), the pathogen was identified as X. campestris pv. campestris. To our knowledge, this is the first report of X. campestris pv. campestris causing black rot on arugula in Argentina. References: (1) J. L. Rademaker et al. Int. J. Syst. Evol. Microbiol. 50:665, 2000. (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.
Acreage of arugula (Eruca sativa), a crucifer used as a component of green salad mixes, has increased recently in Argentina. During 2004, a foliar disease affected commercial crops in Pilar (northeast of Buenos Aires Province). Arugula plants were affected from the seedling stage to harvest. Severely diseased plants were unmarketable and not harvested. Sunken, round, necrotic lesions (1 to 4 mm in diameter) were observed on the cotyledons. Diseased leaves had irregular, necrotic lesions (2 to 3 mm in diameter) that sometimes became confluent, forming a linear pattern. Necrotic tan patches developed on older leaves. Lesions on the abaxial surface appeared depressed and a gray mold, a typical sign of a downy mildew, was visible. Sporangiophores had dichotomous branches ending in slender curved tips. Sporangia were ovoid with a mean length of 20 μm (17.8 to 22.1 μm) and a mean width of 16 μm (14 to 18.2 μm). Pathogenicity tests were conducted by placing excised diseased leaves onto healthy 30-day-old arugula plants (1). Inoculated plants were placed in plastic bags, previously sprayed with water, for 48 h and maintained in the greenhouse thereafter. Downy mildew symptoms and signs that were similar to those observed in the fields developed 10 days after inoculation. The pathogen was identified as Peronospora parasitica (2). To our knowledge, this is the first report of P. parasitica on arugula in Argentina. References: (1) S. T. Koike. Plant Dis. 82:1063, 1998. (2) W. D. Yerkes and C. G. Shaw. Phytopathology 49:499, 1959.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.