IntroductionFungal pathogens cause major yield losses in agriculture and reduce food quality and production worldwide.PurposeTo evaluate new safer alternatives to chemicals for disease management and preserve the shelf life of food, this research was conducted to: determine the chemical composition of the essential oils (EOs) of Thymus serpyllum and Thymus piperella chemotypes 1 and 2; investigate the antifungal potential of EOs in vitro against: Alternaria alternata, Bipolaris spicifera, Curvularia hawaiiensis, Fusarium oxysporum f. sp. lycopersici, Penicillium italicum, Botryotinia fuckeliana; evaluate a natural T. serpyllum extract biofilm to conserve rice grain and cherry tomatoes.MethodEOs were analyzed by GC-MS+GC-FID. EOs’ antifungal activity was evaluated by dissolving Thymus extracts in PDA. Petri dishes were inoculated with disks of each fungus and incubated at 25°C for 7 days.ResultsThe T. serpyllum EO displayed the best Mycelial Growth Inhibition. The antifungal effect of the T. serpyllum EO biofilm was evaluated on rice caryopsis. Disinfected grains were dipped in a conidial suspension of each fungus and sprayed with EO (300 and 600 μg/mL) prepared in Tween 20. Grains were stored. The percentage of infected grains was recorded for 30 days. The T. serpyllum EO effect on cherry tomato conservation was evaluated in vivo. Wounded fruit were immersed in the T. serpyllum EO (300 and 400 μg/mL) and inoculated with Fusarium oxysporum f. sp. lycopersici. Fruit were evaluated for 7 and 14 days. Chemical profiles thymol/carvacrol for T. serpyllum, carvacrol for T. piperella Tp1 and thymol for T. piperella Tp2 were defined. The three evaluated EOs reduced all the studied phytopathogens’ fungal growth. The T. serpyllum biofilm was effective with rice storage and against Fusarium oxysporum f. sp. lycopersici for extending the shelf life of tomatoes in warehouses and storing postharvest cherry tomatoes.ConclusionWe suggest applying these EOs as biofilms for safe food conservation to replace synthetic products.

Charcoal rot, caused by Macrophomina phaseolina (Tassi) Goid., is one of the world's most serious diseases because it reduces yield and seed quality. Nowadays, biological control is an environment-friendly option for controlling plant diseases. The goals of this study were to (i) test eight endophytic Trichoderma spp. strains as biocontrol agents against M. phaseolina and (ii) further investigate two selected strains showing good behaviour against the pathogen. Pathogen-antagonist interactions were studied in dual culture, and the morphological alterations of M. phaseolina mycelia in the interaction zone were examined by light microscopy. Trichoderma strains were applied to soya bean seeds by a seed coating technique. Their bioprotective effects were assessed by in vitro and in vivo assays to evaluate radicle length, the germination percentage and the presence of typical charcoal rot symptoms in seedlings. Two Trichoderma strains were selected and they were molecularly identified as T. harzianum species complex. Their antagonistic ability against M. phaseolina was evaluated under different water availability conditions. The mechanisms used by these two endophytic strains against the pathogen were evaluated by cryo-scanning electron microscopy. The results showed that all eight Trichoderma strains successfully performed biocontrol activity against M. phaseolina by reducing colony growth and causing morphological alterations in the mycelia of M. phaseolina. All endophytes improved seed germination and radicle length, and reduced typical symptoms and disease progression on seedlings. Water availability in the medium impacted on fungal growth. At 0.995 ɑw, all the fungi grew more and faster. At 0.95 ɑw M. phaseolina grew more than the Trichoderma strains, while the pathogen grew slightly more at 0.98 ɑw than the Trichoderma strains. However, both selected Trichoderma strains grew larger and faster than the pathogen at 0.995 ɑw. The mechanisms involved in pathogen control revealed by the light and cryo-scanning microscopy studies included competition for nutrients or space and direct mycoparasitism. All the endophytic Trichoderma strains were antagonistic against M. phaseolina, however our study allowed us to select two Trichoderma strains with good potential to be included for charcoal rot management.

An endophytic fungus isolated from healthy wheat seeds cultivar Klein Yarara in Buenos Aires Province, Argentina, was initially identified as belonging to the Fusarium fujikuroi species complex based on morphological and cultural characteristics. The fungus role in pathogenicity was investigated by artificial inoculation of wheat seeds. Symptoms evaluated 7 and 14 days after inoculation showed that the fungus was pathogenic on seed and seedlings causing symptoms as seed decay, seedling blight and seed rot. The fungus was re-isolated to fulfill Koch's Postulates and was identified as F. sudanense (strain LBEA 3100), a new species recorded in Argentina. The fungal identity was corroborated using molecular techniques by sequencing the ITS region, D1/D2 domains of the LSU gene and TEF-1 alpha region and by comparison with international databases. Ecophysiological studies of F. sudanense (LBEA 3100) performed at different water activities and temperatures showed faster growth rate at the highest water activity and 25 degrees C. This is the first report of F. sudanense, isolated from healthy wheat seeds, causing typical symptoms of seedling blight and seed rot on wheat. (C) 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.

Fusarium sudanense is a novel fungus recently isolated from asymptomatic samples of wheat grains in Argentina. The fungus caused symptoms of seedling blight and seed rot on wheat after artificial inoculations. It is known that the production of mycotoxins by pathogens belonging to the Fusarium genus is harmful to human and animal health. Moreover, the warm and humid conditions that are favorable for growth and mycotoxin production of these species put the Argentinian wheat production area at a high risk of mycotoxin contamination with this novel pathogen. The aim of this work was to evaluate the antagonistic effect of Trichoderma harzianum against F. sudanense under in vitro tests at different environmental conditions. Fungi were screened in dual culture at different water activities (αw) (0.995, 0.98, 0.95, and 0.90) and temperatures (25 and 15 °C). The growth rate of the fungi, interaction types, and dominance index were evaluated. Also, the interaction between T. harzianum and F. sudanense was examined by light and cryo-scanning microscopy. T. harzianum suppressed the growth of F. sudanense at 0.995, 0.98, and 0.95 αw at 25 °C and 0.995 and 0.98 αw at 15 °C. Macroscopic study revealed different interaction types between F. sudanense and T. harzianum on dual culture. Dominance on contact where the colonies of T. harzianum overgrew the pathogen was the most common interaction type determined. The competitive capacity of T. harzianum was diminished by decreasing the temperature and αw. At 0.95 αw and 15 °C, both fungi grew slowly, and interaction type "A" was assigned. Microscopic analysis from the interaction zone of dual cultures revealed an attachment of T. harzianum to the F. sudanense hyphae, penetration with or without formation of appressorium-like structures, coiling, plasmolysis, and a veil formation. According to our results, T. harzianum demonstrated capability to antagonize F. sudanense and could be a promising biocontrol agent.

The abundance of Zymoseptoria tritici ascospores and conidia in a field was examined throughout two one-year periods (1998-1999 and 1999-2000) establishing the relationship between spore release and weather variables. Radiation, temperature, intensity of rainfall, and relative humidity significantly affected the dispersal of ascospores and pycnidiospores of this pathogen. Spore traps collected both types of spores, at weekly intervals, at two different stages of the wheat crop (vegetative and wheat stubble stages) and different distances from the sources. Ascospores were the predominant sources of inoculum in the field. The numbers of ascospores and pycnidiospores declined with the increase of distance from the sources. The release of pycnidiospores was associated with the increase in rainfall intensity 7 days before the released event and the increase in radiation 60 days before the same event. Relative humidity 3 and 15 days before the release event was positively correlated with ascospores release and negatively correlated with radiation and temperature in all the sampling interval. Also for the first time, a positive correlation between radiation and pycnidiospores dispersal is reported. Understanding the relationship between environment conditions and spores dispersal event could improve the control strategies of the disease.

El articulo aborda una innovacion didactica que se diseno con la finalidad de incrementar el nivel de motivacion y autoconfianza de los estudiantes en el desafio y esfuerzo por aprender fitopatologia y, asimismo, procura mejorar la construccion de conocimientos integrados en los contenidos de la disciplina. La innovacion pretende contribuir al desarrollo de habilidades y actitudes relevantes para el desempeno profesional en el sector agropecuario y forestal. La propuesta surgio a partir de problematicas observadas que se manifestaban en actitudes de desinteres o falta de motivacion para el estudio por parte de los estudiantes y en dificultades para lograr la articulacion de saberes relacionados a los contenidos de la asignatura. Asimismo, se partio de asumir que la ensenanza constituye una variable critica en la mejora de la motivacion y en la calidad del aprendizaje que construyen los estudiantes. Para comprender esta problematica se realizo un relevamiento de informacion a traves de entrevistas a docentes del curso y encuestas a estudiantes llevando a cabo un analisis y triangulacion de ambas perspectivas. Se diseno una innovacion a implementarse desde el inicio del curso con el desarrollo del primer trabajo practico y con una propuesta de integracion curricular de resolucion a lo largo del cuatrimestre. La primera actividad practica se propone para ser realizada en el medio productivo propiciando situaciones didacticas en las que los estudiantes aborden problematicas fitopatologicas reales. Asimismo, se pretende que el trabajo de integracion favorezca la construccion de relaciones conceptuales significativas entre contenidos de la fitopatologia considerados de relevancia asi como el aprendizaje en la dimension procedimental y su articulacion.

Endophytes from wheat cultivars isolated in Buenos Aires province, Argentina, were assessed for their potential as biocontrol agents against Pyrenophora tritici-repentis (Died.) Drechsler (anamorph Drechslera tritici-repentis) (Died.) Shoem (Dtr), the causal agent of tan spot of wheat. Endophytes were screened using dual culture techniques and examining the effect on growth, sporulation and the antifungal activity in greenhouse assays. The most of endophytes tested significantly reduced Dtr growth compared to the control except Rhodotorula rubra from 11 to 15 days post inoculation. Trichoderma hamatum, Penicillium sp., Bacillus sp. and Paecilomyces lilacinus significantly reduced the colony diameter of the pathogen. Most of the endophytes evaluated showed morphological changes in the conidia and/or the mycelia of D. tritici-repentis. In addition, two endophytes, Bacillus sp. and Fusarium sp., reduced significantly the percent spore germination of Dtr compared to the control by 82% and 52% respectively. In greenhouse experiment T. hamatum, Chaetomium globosum and Fusarium sp. significantly (P <= 0.05) reduced the average disease severity on all three leaves compared to the control. However, the best antagonistic effect was shown with T. hamatum as it resulted in the greatest suppression in the greenhouse and in the dual-plate assays. Likewise, Bacillus sp. was other highlighted microorganism that antagonized the pathogen in in vitro assays. From our promising results, we conclude that endophytes have potential in the biological control of tan spot of wheat caused by D. tritici-repentis, particularly T. hamatum and Bacillus sp. (C) 2015 Elsevier Inc. All rights reserved.

Bauhinia forficata subsp. pruinosa is a common perennial tree species native to South America that belongs to the Fabaceae. In December 2010 and 2011, plants from a nursery located in the province of Buenos Aires, Argentina presented typical symptoms of anthracnose. We isolated from the lesions of diseased leaves a fungus that based on morphological as well as the ITS (KC132841) and β-tubulin sequences (KJ829534) was identified as Colletotrichum siamense. After 12 days leaves inoculated with the fungal spore suspension developed lesions similar to those observed in natural infections. The fungus was then re-isolated fulfilling Koch's Postulates. To our knowledge, this is the first report of Colletotrichum siamense causing anthracnose in Bauhinia forficata subsp. pruinosa in Argentina.

A severe leaf spot disease was observed on pink lapacho trees, Handroanthus impetiginosus for the first time in Buenos Aires province, Argentina during the autumn of 2013. The pathogen was identified as Alternaria alternata based on the morphological characteristics and sequence data from the internal transcribed spacer region of ribosomal DNA, and partial β-tubulin sequence. A pathogenicity test was performed and Koch’s postulates were confirmed by re-isolating the fungus from artificially inoculated leaves. This is the first report of Alternaria black spot of Handroanthus impetiginosus trees.

Diseases caused by Alternaria sp. are among the most common diseases of crops throughout the world. Alternaria sp. is a common component of the flora of wheat seed. Although isolation of Alternaria sp. from wheat (Triticum aestivum) seed has been reported in Argentina, development of the Alternaria blight in plants from infected seeds has not been demonstrated experimentally. Seed transmission of strains belonging to Alternaria tenuissima, A. alternata, A. infectoria, A. triticina, A. chlamydospora and related genera like Embellisia and Ulocladium sp. on wheat were investigated in the Argentinean growing area, on wheat cultivars Klein Escorpion and Buck Poncho. A. tenuissima was the dominant fungus in black pointed kernels. Transmission of all 42 seed-borne members of Alternaria complex from seeds to seedlings artificially inoculated was detected by trays seedling symptoms test. Among the fungi tested most isolates of Alternaria, Embellisia sp. and Ulocladium sp. produced distinct seed rot and seedling infection symptoms. This confirmed the seed-borne nature of these fungi. In each wheat cultivar tested inoculated seeds appreciably reduced their germination. The emerging coleoptile is externally infected by hyphal growth from the infected pericarp. Typical disease symptoms on the seedlings were exhibited. Recovery of the fungi from asymptomatic coleoptiles was also possible. Transmission efficiency varies with wheat cultivar and ranges from 0 to 92%. These results suggest that infected seed and seed transmission represents a mode of primary source of infection from which these microorganisms can start epidemics to the wheat crop and for dispersal of fungal strains to new areas.

Eje tematico 1: Problematicas y alternativas de mejora de la ensenanza a - La articulacion entre la escuela secundaria y la universidad

Anthracnose symptoms were observed on Blepharocalyx salicifolius from Entre Ríos and Buenos Aires provinces, Eastern Argentina. Colletotrichum gloeosporioides sensu lato (teleomorph Glomerella cingulata) was identified as the causal agent based on disease symptoms, the morphological characteristics of the isolated fungus and pathogenicity tests. To our knowledge, this is the first report of C. gloeosporioides causing leaf spot on Blepharocalyx salicifolius.

Botrytis cinerea (grey mould) is one of the most common diseases of glasshouse crops and is a major cause of plant death in long-season tomato production. A disease management field trial was conducted in a commercial tomato production greenhouse for comparison of seven fungal antagonists which had previously exhibited potential as biological control agents with respect to Botrytis cinerea incidence and severity. Isolates of Trichoderma harzianum, Candida pelliculosa, Rhodotorula rubra, and Fusarium semitectum were recovered from leaves, fruits and flowers of different solanaceous plants. The fungal antagonists were tested for their control of leaf grey mould on tomato under greenhouse conditions during 2008 and 2009. In both years, foliar spray with strains of Trichoderma harzianum and Fusarium semitectum suppressed the foliar infection of B. cinerea. The suspensions of T. harzianum 118 and 252 and F. semitectum 25 significantly reduced disease incidence (65-95%) and severity (50-77%) in inoculated plants compared to untreated controls (P <= 0.05). Our results suggest that formulations of saprophytic fungi selected from the naturally occurring mycoflora could be an effective tool in the biological control of tomato grey mould.

Plants harbour a heterogeneous population of endogenous microorganisms, comprising both pathogens and non-pathogens, including fungi, bacteria, actinomycetes, etc. Their association has substantial impact on plant health and fitness. Endophytes reside inside healthy plant tissues without producing any disease symptoms. They are helpful in modifying biochemicals produced by plants and may add to their protection from insect herbivores, fungal pathogens and even grazing by animals. However, the ecological role of these endophytes is not yet fully understood. This chapter reports on endophytic fungi present in beet and tomato leaves. Isolation and analysis of endophytic microorganisms of soybean and wheat are also described. It is advocated that endophytes may have a definite role in the biological control of Drechslera tritici-repentis, responsible for tan spot disease in wheat.

In order to evaluate the potential of naturally occurring filamentous fungi having potential as biocontrol agents effective against grey mould and post-harvest fruit rot caused by Botrytis cinerea on tomato, fungal saprophytes were isolated. They were obtained from leaves, fruits and flowers belonging to different species of cultivated and spontaneous Solanaceous plants collected at the horticultural area of La Plata, Argentina. Of 300 isolates screened for inhibition of B. cinerea using the dual culture technique on agar plate, 12 strains inhibited strongly mycelial growth of the pathogen. Among the antagonists one isolate of Epicoccun nigrum (126), four of Trichoderma harzianum (110, 118, 248 and 252) and four isolates of Fusarium spp. decreased the spore germination of B. cinerea between 30 and 70%. These isolates were probed on tomato fruits to evaluate their biocontrol activity against post-harvest grey mould. In growth chamber tests, E. nigrum (27), F. equiseti (22, 105) and T. harzianum (118, 252) reduced the diameter of fruit lesions by 50 – 90% and were selected for further biocontrol assays of tomato plants in the greenhouse. Although there were not significant differences between the treatments and the control, F. equiseti (105), E. nigrum (27) and T. harzianum (118) reduced by 20, 22 and 22 respectively the disease on whole plants. The targeted application of isolates of E. nigrum, T. harzianum and F. equiseti provides a promising alternative to the use of fungicide spray to control B. cinerea on tomatoes.

In Argentina, celery is grown in the outskirts of the principal cities in the provinces of Buenos Aires, Santa Fe, and Mendoza. Since the late 1990s, plants growing in La Plata (Buenos Aires) have shown rapid decline in commercial fields. Symptoms are delayed growth, yellowed leaves, discoloured vascular tissue and reduced root system. The objectives of this work were to determine the causal agent of the disease and to analyze the effects of inoculum levels on the disease. Fusarium oxysporum (Fo) was consistently isolated on potato-dextrose-agar (PDA). The "forma specialis" was identified by pathogenicity tests where each of seven selected strains of Fo on colonized rice that was dried and ground were mixed into soil. Initial Fusarium wilt symptoms were recorded 50 days after inoculation, and PO was reisolated from affected roots, stems, crowns, and petioles suggesting that the pathogen is Fo f. sp. apii (Foa). In another assay different concentrations of inoculum (10(1) to 10(4) cfu per g of soil) were tested to determine the effects of Foa on the plants (cv. Golden Boy). Wilt severity, chlorosis, plant height, and dry weight were assessed weekly. Typical symptoms developed at all levels of inoculum. Disease severity increased when the inoculum density was increased. To our knowledge, this is the first report of Foa in Argentina. The possibility that the pathogen was introduced on imported seed during the last few years is discussed.

In order to study the species composition of endophytes from wheat healthy plants in Buenos Aires Province (Argentina) and to determine their infection frequencies from leaves, stems, glumes and grains, wheat plants were collected from five cultivars at five growth stages from crop emergence to harvest. A total of 1,750 plant segments (leaves, stems, glumes and grains) were processed from the five wheat cultivars at five growth stages, and 722 isolates of endophytic fungi recovered were identified as 30 fungal genera. Alternaria alternata, Cladosporium herbarum, Epicoccum nigrum, Cryptococcus sp., Rhodotorula rubra, Penicillium sp. and Fusarium graminearum were the fungi that showed the highest colonization frequency (CF%) in all the tissues and organs analysed. The number of taxa isolated was greater in the leaves than those in the other organs analysed.

In the autumn and winter of 2005 severe attacks by a foliar disease were observed on rocket (Eruca sativa) in a commercial greenhouse in La Plata, Buenos Aires, Argentina. The disease affected newly expanded leaves of plants 15–20 days old. The etiology of the disease was investigated. The disease was identified as downy mildew caused by Peronospora parasitica. Pathogenicity was confirmed by pressing one adaxial infected leaf with abundant sporulation onto one adaxial healthy leaf. Downy mildew developed on inoculated plants after 8 days and the pathogen morphology matched that of the originally identified pathogen. In the same field, symptoms of downy mildew caused by P. farinosa were observed on swiss chard (Beta vulgaris var. cicla). The pathogenicity of this fungus on rocket was confirmed. This is the first report of downy mildew on rocket caused by Peronospora parasitica in Argentina.