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

Examination of meteorology-based predictions of Fusarium head blight of wheat grown at two locations in the southern Pampas region of Argentina

In Argentina, head blight or scab is a highly risky disease (caused by Fusarium graminearum) of wheat, although its occurrence is sporadic depending on prevalent environmental variables. These traits stimulated the development of predictive models of head blight epidemics, which would help growers in the selection of control strategies. Regression models for predicting head blight incidence were developed at Pergamino (33°56S, 60°30W), associating temperature and moisture variables with mean disease data (empirical approach). Recently a new fundamental-empirical approach for estimating Fusarium index (incidence%×severity%/100) was developed using data from Pergamino and Marcos Juarez (32°41′S, 62°07′W). Validation studies of both empirical and fundamental-empirical approaches were carried out at northern and southern locations showing good results after making a few changes. The objective of this work was to examine the goodness of fit of the predicted values from both approaches (original and including some of the changes derived from previous validation studies) in comparison with median disease data in two southern locations of the Pampas region: Balcarce (37°45′S, 58°18′W) and Barrow (38°19′S, 60°15′W), for the 2002, 2003 and 2004 wheat seasons. Partial and mean deviation values between observed and predicted data were calculated. In accordance with previous validation studies, successful Fusarium index estimations were achieved decreasing the heat accumulation defining the length of the wheat critical period for infection to 450 degree days [base mean daily temperature (Td)=10°C]. Reducing the critical period length [450 degree days (base Td=0°C) instead of 530] and increasing maximum and minimum temperature thresholds (30° instead of 26°C and 11°C instead of 9°C) of the empirical equation thermal variable led to satisfactory Fusarium incidence predictions. This study showed that both approaches developed at northern locations of the Pampas region can be portable and useful for predicting disease intensity at more southern locations, making only a few changes. Differences in wheat cultivar behaviour regarding the disease were observed in the analysed data but this effect was not considered in this study.Centro de Investigaciones en Fitopatologí

Meteorological-Based Predictions of Wheat Head Blight Epidemic in the Southern Argentinean Pampas Region

In Argentina, head blight is a highly risky disease (caused by Fusarium graminearum), although its occurrence is sporadic depending on prevalent environmental variables. These traits stimulated the development of predictive models of head blight occurrence which would help growers in the selection of control strategies. Empirical equations for predicting head blight incidence were developed at Pergamino (33° 56′ S, 60° 30′ W) associating temperature and moisture variables with mean disease data. Recently a new fundamental-empirical approach for estimating Fusarium index (incidence% x severity%/100) was developed using data of Pergamino and Marcos Juarez (32° 41′ S, 62°07′ W). In this study our objective was to validate both approaches at three more southern locations: La Dulce (38° 10′ S, 58° 00′ W), Miramar (38° 00′ S, 57° 33′ W) and Balcarce (37° 45′ S, 58° 18W), for the 2001 crop season. Examining partial and mean deviation values between observed and predicted incidence data, an underestimation especially at La Dulce was assessed. A clear improvement of incidence goodness of fit estimations was obtained decreasing the heat accumulation defining the length of the wheat critical period for infection. Employing this last critical period length for the fundamental-empirical approach led to satisfactory Fusarium index predictions. This study showed that both approaches developed at northern locations of the Pampas region can be portable and useful for predicting disease intensity at more southern locations, making only a few changes.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

Weed diseases in La Plata area II. Identification of pathogens with potentitial for weed biocontrol programmes

En este trabajo se completa el estudio de las enfermedades halladas en un grupo de malezas del cinturón hortícola platense, Provincia de Buenos Aires, y de la capacidad potencial de los respectivos patógenos para emplearlos como biocontrol adores. Fueron registradas 21 especies fúngicas sobre los siguientes hospedantes: Anoda cristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare,Commelina erecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiolacaroliniana, Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchusoleraceus, Urtica urens, Wedelia glauca y Xanthium cavanillesii. A partir de tos resultados que surgieron de los estudios etiosintomatológicos, como así también de las observaciones del daño producido e intensidad de ataque, pudo determinarse que los microorganismos con posibilidades de constituirse en agentes de biocontrol son: Alternaría sp sobre W. glauca; Puccinia calcitrapae sobre C. vulgare: P. heterospora sobre A. cristata: P.modiolae sobre M. multifida; P.polygoni-amphibii sobre P. convolvulus; Septoria urticae sobre U. urens: Uromycesbidenticola sobre B. subalternaos y U. commelinae sobre C. virginica.The aim of this research was to study fungal diseases found on weeds of vegetable crops of the rural belt of La Plata (Buenos Aires Province). In order to establish the poteniial of the microorganisms as biological control agenfs, the level of damage caused by the pathogens was also determined. Twenty-one species of fungi were recorded from the following hosts: Anodacristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare, Commelinaerecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiola caroliniana,Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchus oleraceus, Urticaurens, Wedelia glauca y Xanthium cavanillesii.Facultad de Ciencias Agrarias y Forestale

Weed diseases in La Plata area II. Identification of pathogens with potentitial for weed biocontrol programmes

En este trabajo se completa el estudio de las enfermedades halladas en un grupo de malezas del cinturón hortícola platense, Provincia de Buenos Aires, y de la capacidad potencial de los respectivos patógenos para emplearlos como biocontrol adores. Fueron registradas 21 especies fúngicas sobre los siguientes hospedantes: Anoda cristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare,Commelina erecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiolacaroliniana, Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchusoleraceus, Urtica urens, Wedelia glauca y Xanthium cavanillesii. A partir de tos resultados que surgieron de los estudios etiosintomatológicos, como así también de las observaciones del daño producido e intensidad de ataque, pudo determinarse que los microorganismos con posibilidades de constituirse en agentes de biocontrol son: Alternaría sp sobre W. glauca; Puccinia calcitrapae sobre C. vulgare: P. heterospora sobre A. cristata: P.modiolae sobre M. multifida; P.polygoni-amphibii sobre P. convolvulus; Septoria urticae sobre U. urens: Uromycesbidenticola sobre B. subalternaos y U. commelinae sobre C. virginica.The aim of this research was to study fungal diseases found on weeds of vegetable crops of the rural belt of La Plata (Buenos Aires Province). In order to establish the poteniial of the microorganisms as biological control agenfs, the level of damage caused by the pathogens was also determined. Twenty-one species of fungi were recorded from the following hosts: Anodacristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare, Commelinaerecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiola caroliniana,Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchus oleraceus, Urticaurens, Wedelia glauca y Xanthium cavanillesii.Facultad de Ciencias Agrarias y Forestale

Examination of meteorology-based predictions of Fusarium head blight of wheat grown at two locations in the southern Pampas region of Argentina

In Argentina, head blight or scab is a highly risky disease (caused by Fusarium graminearum) of wheat, although its occurrence is sporadic depending on prevalent environmental variables. These traits stimulated the development of predictive models of head blight epidemics, which would help growers in the selection of control strategies. Regression models for predicting head blight incidence were developed at Pergamino (33°56S, 60°30W), associating temperature and moisture variables with mean disease data (empirical approach). Recently a new fundamental-empirical approach for estimating Fusarium index (incidence%×severity%/100) was developed using data from Pergamino and Marcos Juarez (32°41′S, 62°07′W). Validation studies of both empirical and fundamental-empirical approaches were carried out at northern and southern locations showing good results after making a few changes. The objective of this work was to examine the goodness of fit of the predicted values from both approaches (original and including some of the changes derived from previous validation studies) in comparison with median disease data in two southern locations of the Pampas region: Balcarce (37°45′S, 58°18′W) and Barrow (38°19′S, 60°15′W), for the 2002, 2003 and 2004 wheat seasons. Partial and mean deviation values between observed and predicted data were calculated. In accordance with previous validation studies, successful Fusarium index estimations were achieved decreasing the heat accumulation defining the length of the wheat critical period for infection to 450 degree days [base mean daily temperature (Td)=10°C]. Reducing the critical period length [450 degree days (base Td=0°C) instead of 530] and increasing maximum and minimum temperature thresholds (30° instead of 26°C and 11°C instead of 9°C) of the empirical equation thermal variable led to satisfactory Fusarium incidence predictions. This study showed that both approaches developed at northern locations of the Pampas region can be portable and useful for predicting disease intensity at more southern locations, making only a few changes. Differences in wheat cultivar behaviour regarding the disease were observed in the analysed data but this effect was not considered in this study.Centro de Investigaciones en Fitopatologí

Meteorological-Based Predictions of Wheat Head Blight Epidemic in the Southern Argentinean Pampas Region

In Argentina, head blight is a highly risky disease (caused by Fusarium graminearum), although its occurrence is sporadic depending on prevalent environmental variables. These traits stimulated the development of predictive models of head blight occurrence which would help growers in the selection of control strategies. Empirical equations for predicting head blight incidence were developed at Pergamino (33° 56′ S, 60° 30′ W) associating temperature and moisture variables with mean disease data. Recently a new fundamental-empirical approach for estimating Fusarium index (incidence% x severity%/100) was developed using data of Pergamino and Marcos Juarez (32° 41′ S, 62°07′ W). In this study our objective was to validate both approaches at three more southern locations: La Dulce (38° 10′ S, 58° 00′ W), Miramar (38° 00′ S, 57° 33′ W) and Balcarce (37° 45′ S, 58° 18W), for the 2001 crop season. Examining partial and mean deviation values between observed and predicted incidence data, an underestimation especially at La Dulce was assessed. A clear improvement of incidence goodness of fit estimations was obtained decreasing the heat accumulation defining the length of the wheat critical period for infection. Employing this last critical period length for the fundamental-empirical approach led to satisfactory Fusarium index predictions. This study showed that both approaches developed at northern locations of the Pampas region can be portable and useful for predicting disease intensity at more southern locations, making only a few changes.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

Fusarium spp in wheat, toxicogenic capacity and chemotaxonomy of the strains isolated in Argentina

Se aislaron e identificaron 91 cepas de Fusarium spp (F graminearum, F equiseti, F moniliforme, F m var anthophilum, F acuminatum, F solani y F oxisporum) a partir de semillas de trigo pan procedentes de 17 localidades trigueras de la República Argentina. Mediante el cultivo de las mismas en arroz pelado y pulido se evaluó la producción de tricotecenos y zearalenona, a los efectos de revelar si existen diferencias regionales en cuanto a su presencia. Se detectaron cepas productoras de tricotecenos del grupo B y zearalenona, no habiéndose hallado productoras del grupo A. De las cepas evaluadas el 82,4% produjeron tricotecenos que se subdividieron en dos grupos: a) las cepas productoras de deoxinivalenol (DON) y su precursor 3 acetil-deoxinivalenol (AcDON) y b) las productoras de nivalenol (NIV) y su precursor 4 acetil-nivalenol o fusarenona-x (FUS-X). Los resultados demostraron que el 48,3% de las cepas fueron productoras de DON, el 7,7% de NIV y el 26,4% tuvieron la capacidad de producir simultaneamente DON y NIV en los cultivos. Al considerar exclusivamente las cepas de F graminearum el 89,4% fueron toxicogénicas, de ellas el 55,9% pertenecieron al quimiotipo DON, 10,3% al quimiotipo NIV y 33,8% produjeron DON y NIV. En cuanto a la zearalenona (ZEA) el 63,2% del total de las cepas fueron productoras de esta toxina, no existiendo ninguna relación entre los grupos DON y NIV con la producción de ZEA. La distribución de las cepas toxicogénicas de Fusarium spp observada en las distintas localidades de la República Argentina, permite inferir la existencia de diferencias regionales en el área triguera.In wheat seeds from 17 different wheat growing sites, 91 Fusarium spp strains (F graminearum, F equiseti, F moniliforme, F m var anthophilum, F acuminatum, F solani and F oxysporum) were isolated and identified. The production of trichothecenes and zearalenone was evaluated after growing them on peeled and polished rice to find out if there were any regional differences in their prevalence. Strains producing trichothecenes of the B group and zearalenone were detected; no producers of the A groups were found. From the strains studied, 82.4% produced trichothecenes, and could be divided into 2 groups: a), deoxynivalenol (DON) producing strains and its precursor 3 acetyldeoxynivalenol (AcDON); and b), nivalenol (NIV) producing strains and its precursor 4 acetylnivalenol or fusarenone-x (FUS-X). The results showed that 48.3% of the strains were DON producers, 7.7% NIV producers and 26.4% produced both DON and NIV. Eighty-nine point four percent Fgraminearum strains were toxigenic; among them 55.9% were DON chemotype, 10.3% NIV chemotype and 33.8% produced DON and NIV. Sixty-three point two percent of the strains also produced zearalenone (ZEA), no relation existing between the DON and NIV groups with regard to ZEA production. The finding of certain toxigenic strains in various sites in Argentina allows us to conclude that regional differences exist.Facultad de Ciencias Agrarias y Forestale