Occurrence of <i>Drechslera avenae</i> on durum wheat (<i>Triticum durum</i>) seed in Argentina

Drechslera avenae was isolated from durum wheat seeds from Buenos Aires Province, Argentina, following ISTA protocols. Two assays using artificial inoculation of seed were performed to determine the pathogenicity of this fungus to durum seeds. The infection rates obtained (21–26%) demonstrate the importance of this fungus as a potential seedborne pathogen of durum wheat. This is the first record of D. avenae parasitising durum wheat seed in Argentina.Centro de Investigaciones en FitopatologíaComisión de Investigaciones Científicas de la provincia de Buenos Aire

Formation of Lewia infectoria, the teleomorph of Alternaria infectoria, on wheat in Argentina

The trapping of pseudothecia carrying asci with mature ascospores of Lewia infectoria (teleomorph of Alternaria infectoria) from wheat stubble under natural field conditions in Buenos Aires Province, Argentina, is reported for the first time. The production of mature pseudothecia in culture is also reported. Monosporic isolates of A. infectoria, obtained from infected wheat plants in Argentina, produced conidia within a week and ascomata with fully mature ascospores within 7 months when stored on slants of PCA at 4°Cin darkness. The anamorph exhibited the sporulation pattern of Alternaria infectoria species-group, and was identified by its axenic colony morphology and the prominence of its secondary conidiophore structure. Critical examination of the teleomorph revealed it to be Lewia infectoria. The presence of the teleomorph has implications in the long-distance dispersal of A. infectoria and on resistance breeding programs. This is the first confirmed report of the sexual stage of A. infectoria in Argentina.Centro de Investigaciones en Fitopatologí

Wheat fusarium head blight 2001 epidemic in the southern Argentinian pampas

Wheat Head Blight or Scab is frequently a destructive fungal disease caused by several Fusarium species but F. graminearum Schwabe [teleomorph Gibberella zeae (Schwein) Petch; synonym = G. saubinetii (Mont.) Sacc.] is the principal causal agent. The disease is common in humid and semi-humid wheat (Triticum spp.) cropping areas around the world. Epidemics of Fusarium head blight (FHB) seem to be increasing globally during the last two decades. In Argentina and some other countries of South America, damages have been very significant. In the USA, Canada and other wheat cropping areas, several harvests have been affected by numerous epidemics.Facultad de Ciencias Agrarias y Forestale

Alternaria infectoria species-group associated with black point of wheat in Argentina

Regional surveys are being conducted in Argentina to assess the presence of wheat (Triticum aestivum) pathogens on grains across the main cropping area. During 2001 and 2002, grain samples with a dark brown or blackish discoloration around the embryo end, known as black point, were observed on several cultivars across the wheat region of Buenos Aires Province.Centro de Investigaciones de Fitopatologí

Alternaria infectoria species-group associated with black point of wheat in Argentina

Regional surveys are being conducted in Argentina to assess the presence of wheat (Triticum aestivum) pathogens on grains across the main cropping area. During 2001 and 2002, grain samples with a dark brown or blackish discoloration around the embryo end, known as black point, were observed on several cultivars across the wheat region of Buenos Aires Province.Centro de Investigaciones de Fitopatologí

A Scale for Appraising the Leaf Blight of Wheat Caused by Alternaria Triticimaculans

The aim of this work was to present an scale of measurement for appraising the progress of leaf blight of wheat (Alternaria triticimaculans) in the field. Approximately three hundred diseased leaves of wheat at the milky ripe stage from an artificially inoculated crop, were collected. Based on leaf affected area in relation to the total leaf area, a nine grade scale was propose as a rapid technique to estimate this foliar disease.Facultad de Ciencias Agrarias y Forestale

Formation of Lewia infectoria, the teleomorph of Alternaria infectoria, on wheat in Argentina

The trapping of pseudothecia carrying asci with mature ascospores of Lewia infectoria (teleomorph of Alternaria infectoria) from wheat stubble under natural field conditions in Buenos Aires Province, Argentina, is reported for the first time. The production of mature pseudothecia in culture is also reported. Monosporic isolates of A. infectoria, obtained from infected wheat plants in Argentina, produced conidia within a week and ascomata with fully mature ascospores within 7 months when stored on slants of PCA at 4°Cin darkness. The anamorph exhibited the sporulation pattern of Alternaria infectoria species-group, and was identified by its axenic colony morphology and the prominence of its secondary conidiophore structure. Critical examination of the teleomorph revealed it to be Lewia infectoria. The presence of the teleomorph has implications in the long-distance dispersal of A. infectoria and on resistance breeding programs. This is the first confirmed report of the sexual stage of A. infectoria in Argentina.Centro de Investigaciones en Fitopatologí

Estudios preliminares de biocontrol de mancha en red de la cebada en semilla, con cepas de Trichoderma spp. Ensayos in vitro

La “mancha en red” de la cebada, producida por el hongo Drechslera teres (Sacc.) Shoem. (teleomorfo Pyrenophora teres Drechsler) es una enfermedad endémica en la Argentina, llegando a tener una prevalencia del 76 % e incidencia del 100%, presentándose desde el estado de plántula hasta la cosecha. Produce pérdidas en el rendimiento del 20% y disminuye el peso y cantidad de granos/mt2 . La semilla infectada y el rastrojo son las principales fuentes de inóculo de la enfermedad. Las semillas constituyen el agente más eficiente de diseminación y el medio más seguro para la supervivencia de los patógenos cumpliendo un rol fundamental en sus ciclos de vida. La asociación de los patógenos con las semillas, les asegura la obtención de nutrientes en el momento de la germinación y emergencia de las plántulas (Reis et al., 1999). D. teres, se transmite de la semilla infectada a los órganos aéreos para dar continuidad a su ciclo de vida, con una tasa de transmisión del 21%, por esto el tratamiento de semilla es la clave para impedir la introducción de éste patógeno en los lotes de cultivo.Centro de Investigaciones de Fitopatologí

Estudios preliminares de biocontrol de mancha en red de la cebada en semilla, con cepas de Trichoderma spp. Ensayos in vitro

La “mancha en red” de la cebada, producida por el hongo Drechslera teres (Sacc.) Shoem. (teleomorfo Pyrenophora teres Drechsler) es una enfermedad endémica en la Argentina, llegando a tener una prevalencia del 76 % e incidencia del 100%, presentándose desde el estado de plántula hasta la cosecha. Produce pérdidas en el rendimiento del 20% y disminuye el peso y cantidad de granos/mt2 . La semilla infectada y el rastrojo son las principales fuentes de inóculo de la enfermedad. Las semillas constituyen el agente más eficiente de diseminación y el medio más seguro para la supervivencia de los patógenos cumpliendo un rol fundamental en sus ciclos de vida. La asociación de los patógenos con las semillas, les asegura la obtención de nutrientes en el momento de la germinación y emergencia de las plántulas (Reis et al., 1999). D. teres, se transmite de la semilla infectada a los órganos aéreos para dar continuidad a su ciclo de vida, con una tasa de transmisión del 21%, por esto el tratamiento de semilla es la clave para impedir la introducción de éste patógeno en los lotes de cultivo.Centro de Investigaciones de Fitopatologí

Fusarium graminearum and deoxynivalenol contamination in the durum wheat area of Argentina

Fusarium graminearum head blight of wheat is a destructive disease of the world's wheat-growing areas. This work was performed to analyze the distribution and contamination of deoxynivalenol (DON) and its relationship with F. graminearum kernel invasion in Argentina durum wheat area during two consecutive harvests. A total of 147 samples (cultivars and lines) of durum wheat from 5 locations of the major cropping area (Southern Buenos Aires Province) were analyzed. Percentage of F. graminearum kernel infection was evaluated following the blotter test (ISTA method) and fusarotoxins were analyzed by thin layer chromatography. None of the varieties and lines were free of F. graminearum infection. In the first harvest fungal invasion was very low. From 40 samples, 55% showed DON contamination but only 4 samples (10%) were higher than 2 ppm. In the second harvest, a crop year conducive to scab development, the highest level of F. graminearum kernel invasion observed was 42% on a sample from the humid area (eastern Buenos Aires Province) DON was detected in 47 (78.2%) of 60 samples analyzed and 19 (31.6%) showed levels of DON higher than those established in the guidelines in Canada and USA for food and feedstuff. In both years all locations situated in the humid area showed levels ranging from 0 to < 8 ppm. Within the durum wheat area differences among locations were found. This analysis indicates the need for more information on the problem and distribution of Fusarium mycotoxins in durum wheat grown in Argentina.Centro de Investigaciones de Fitopatologí