Wheat grain discoloration, a worldwide disease that lowers grain quality and decreases grain yield, does not have a single etiology. It has been proposed that it is a consequence of an abiotic mechanism, a response to environmental conditions or enzymatic activity. It has also been suggest that it is a biotic mechanism, a fungal infection principally by Alternaria spp. and Bipolaris sorokiniana. The present work was carried out to analyze the possible etiology of this disease in nine durum wheat genotypes from two localities of southern Buenos Aires province (Argentina) on two sowing dates. Incidence (percentage of grain discoloration) was recorded and mycobiota associated with this pathology was registered following ISTA rules. Peroxidase activity in an extract obtained from grains belonging to genotypes of the locality that showed the highest incidence was measured. The incidence among genotypes, localities and sowing dates varied, although the genotypes with the higher and lower values of incidence were the same for all the variables tested. The fungus Alternaria spp. was isolated the most frequently followed by Fusarium spp., while Bipolaris sorokiniana was found the least frequently. Peroxidase activity showed that all the treatments had similar levels of enzymatic activity, but there was no clear differentiation between controls either between genotypes with the lowest or the highest incidence values. This suggests that peroxidase activity did not have a clear relationship with grain discoloration. In this research, it is presumed that fungal infection is the main cause of this disease.

Alternaria alternata is one of the main microorganisms responsible for affecting seeds and causing infection and eventually seed discoloration. The purpose of this work was to analyze sanitary quality in seeds of five amaranth genotypes, of which four were late-cycle (160 days) and the remaining one was early-cycle (79 days). Trials were carried out in two consecutive seasons during 2013–2015 following an experimental design set up in completely randomized blocks with three replications. The following variables were analyzed: seed yield per square meter, 1000 seed weight, germination, incidence of seed infection with A. alternata, incidence of seed discoloration in large and small seeds, and mycotoxin contamination. Results showed that in the early genotype infection and seed discoloration produced by A. alternata was lower and mycotoxin content was either lower or null than in late genotypes.

Chaetomium is a ubiquitous genus well known by its properties for agriculture application. In this review, biology and taxonomy mainly of its principal and more studied species group, C. globosum, is presented. Besides, the use of this fungus as plant growth promoter and biocontrol agent through bioformulations, secondary metabolites and enzymes is mentioned. Finally, this review deals with the researches and current status in Argentina.

During the conduction of health tests of barley seeds belonging to crops in Argentina, we observed colonies with the appearance of species in the genus Bipolaris. The organism was subsequently keyed to the specie Bipolaris zeicola based on morphological characteristics. This preliminary identification was confirmed by molecular characterization through an amplification of the internal transcriber spacer and glyceraldehyde-3-phosphate dehydrogenase. The fungal isolate was inoculated onto barley and maize seedlings and produced foliar symptoms in both cereals, producing typical symptoms on maize. The present identification constitutes the first report of Bipolaris zeicola on barley worldwide and the first citation of the presence of this pathogen on any host in Argentina.

The fungus Pyrenophora teres, causal agent of net blotch of barley, generates important yield losses, mainly regarding grain weight and quality of malt extract for beer production. In order to find new strategies to manage this disease, we evaluated in vitro and in vivo antagonistic interactions among different native isolates of Trichoderma spp. and P. teres. The microorganisms were isolated from different barley crop areas of Buenos Aires province and identified according to morphological features and molecular techniques. Dual cultures were conducted to assess in vitro antagonism using direct interactions. Assays under greenhouse conditions were carried out to evaluate the efficiency of Trichoderma spp. as biocontrol and plant growth–promoting agent. In vitro, all Trichoderma spp. isolates inhibited mycelial growth of P. teres in an 18%–54% range compared to the controls. Microscopic observations of interaction zones revealed morphological alterations of P. teres such as vacuolated mycelium without typical pigmentation and coiling. In vivo, all Trichoderma isolates significantly decreased the incidence of P. teres, up to 55% on barley seedlings. Severity decreased up to 77% on stems and up to 70% on leaves. Likewise, regarding growth–promoting parameters, aerial and radicular dry weight of plants treated with Trichoderma spp. increased up to 20% and 15%, respectively. On the other hand, an increase of chlorophyll (SPAD) of up to 9% compared to the control was recorded in seedlings treated with Trichoderma

Many species of Trichoderma produce secondary metabolites such as volatile organic compounds (VOCs) that reduce plant diseases and promote their growth. In this work we evaluated the antagonistic effects of VOCs released by eight strains of two Trichoderma species against Pyrenophora teres Drechsler, the causal agent of barley net blotch. Antagonism was estimated based on the percentage of mycelial growth inhibition according to the confronted cultures method. VOCs extraction and identification were performed by gas chromatography and mass spectrometry, through different methodologies for VOCs emitted by antagonists and pathogens alone or when confronted. VOCs produced by all Trichoderma strains inhibited mycelial growth of the pathogen in a range of 3 to 32%, showing weak and unpigmented mycelia with vacuolization. In addition, P. teres stimulated the release of VOCs by both Trichoderma species. The major groups of VOCs detected were sesquiterpenes, followed by diterpenes, terpenoids and eight-carbon compounds. This is the first report about characterization of volatiles emitted by Trichoderma in the presence of P. teres.

G. paniculata L (“baby’s breath”) is a worldwide crop mainly used as a filler cut flower. It is commercially propagated vegetatively to preserve the ornamental characteristics of the plant. Among fungal diseases caused by soilborne pathogens, Phytophthora species and Rhizoctonia solani, due to their irreversible rotting of plants, are the most devastating Gypsophila disease worldwide. Pythium species and R. solani are especially destructive in the process of rooting cuttings. In adult plants, Fusarium species produce rotting of basal tissues resulting in death. Powdery mildew caused by Erysiphe buhrii is important on aerial parts, producing in some countries nearly 100 % of disease incidence at harvest. Crown gall has been reported in all continents, and few viruses and nematodes are cited.

Fil: Bezus, Rodolfo. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Catedra de Cerealicultura; Argentina

El de los granos de arroz puede ser causado por gran numero de hongos. La presencia de los diversos tipos de manchas o coloracion reduce la calidad del producto. Puede aparecer externamente en las glumelas o internamente en los granos, o ambas. A partir de granos que presentaban esta patologia se describieron los sintomas y se determinaron los agentes involucrados en la misma. Se analizaron semillas del cultivar Irga 409 provenientes de las provincias de Corrientes y Formosa, que serian luego destinadas a consumo bajo el proceso de parbolizado. Se empleo el metodo del papel de filtro (blotter test) segun las normas impartidas por ISTA (International Seed Testing Association). Los sintomas observados fueron diversos: granos con puntuaciones negras, pigmentados, yesosos, manchados, etc. Los hongos involucrados fueron: NN (especie aun no determinada), Curvularia lunata, C. protuberata, Bipolaris oryzae. Epicoccumspp. Alternariasp, Fusarium semitectum, F. equiseti, F. graminearum y F. oxysporum. No se encontro correlacion entre los distintos sintomas observados y cada uno de los diferentes organismos aislados. Aproximadamente un 70% de los granos presentaron como agente asociado a esta alteracion a NN. resultando por lo tanto el hongo de mayor frecuencia de aparicion e importancia en el manchado del arroz.

Carnation (Dianthus caryophyllus L.) is one of the most popular and traditional cut flowers worldwide. This species has been used extensively by breeders for centuries, and as a result many cultivated hybrids exist. Several diseases affect quality. Among fungal diseases caused by soilborne pathogens, Fusarium wilt is the most devastating carnation disease worldwide. None of the management practices currently available completely control Fusarium wilt of carnation; only the integration of different control measures allows management of the disease. The most important bacterial diseases affecting carnation are caused by Burkholderia species. This cut flower is affected by eight viruses that reduce the quantity and quality of production. The vegetative propagation of the crop favors the dispersal of these pathogens as well as the fungi and bacteria that colonize xylem tissues. So, meristem-tip culture of healthy mother plants is recommended. Several plant pathogenic nematode species of different trophic habits can infect carnation. Nevertheless, only root-knot and cyst nematodes, of the genera Meloidogyne and Heterodera, respectively, are of significance because of their economic impact. The integration of different control practices is the best strategy for the management of most diseases.

"Net blotch" (Drechslera teres) and "Bipolaris spot blotch" (Bipolaris sorokiniana) are foliar diseases of barley. Biological control is currently considered as an efficient alternative to chemical management of these plant diseases. The aim of the present study was to identify 2 isolates of Chaetomium (C2 and C5), endophytics on barley seedlings and to study the in vitro interactions with D. teres and B. sorokiniana, isolated from seeds of the same host. Cultural and morphological characterization of all microorganisms was done. In addition, molecular characterization of Chaetomium spp. was conducted and dual culture tests were carried out to find, by microscopic observations, the effects of the antagonist on the morphology of the pathogens. The results confirm the identity of the pathogens and the isolates of Chaetomium spp. as Chaetomium globosum species group. Inhibition of B. sorokiniana and D. teres by C2 and C5 accounted for 30% and 31.2%, and 40% and 36% respectively, compared with the control. The mechanisms of action against B. sorokiniana and D. teres were antibiosis and competition and mycoparasitism, respectively. Microscopic observation revealed deformed conidia in B. sorokiniana and plasmolisis, coiling and orange pigmentation in D. teres.

In the present study the aspects of discolouration that could influence both the production and consumption of amaranth were analyzed with the objectives to identify the presence of Alternaria alternata on seeds, to analyze possible changes in the anatomy of seed tissues and to detect the presence of fungal secondary metabolites. Component plating, histopathological and mycological analyses on discoloured seeds allowed i) location of propagules of A . alternata in all seminal components; ii) observation of hypertrophies in perisperm and embryo and iii) determination of several fungal secondary metabolites, mainly high concentrations of tenuazonic acid. To our knowledge, the information presented in this paper, related to physiological, histopathological changes and fungal secondary metabolites on discoloured seeds of ( Amaranthus mantegazzianus syn. A. caudatus subsp. mantegazzianus (Pass) Hanelt affected by A. alternata , is the first worldwide record.

The rice grain is frequently infected by a series of pathogens (fungi) during its storage, producing damages to the economy and health of humans. The aim of this study was to identify the fungal genera present in different rice genotypes and to quantify their variation during storage. Paddy, brown and milled rice fractions of Nutriar, (N) H329-5(H329) and Don Ignacio genotypes were analyzed at 4, 8 and 12 months of storage. Fungi were identified based on their micromorphological characteristics and colonies. The observed genera according to their frequency were: Alternaria, Nigrospora, Epicoccum, Bipolaris, Curvularia, Cladosporium and Fusarium (field fungi) and Penicillium and Aspergillus (storage fungi). The mycobiota composition was different depending on the grain fraction and the period of storage: field fungi were located in the hulls and bran layers, while storage fungi were mainly in the endosperm. The different genotypes showed different susceptibility to contamination.

Fil: Moya, Paulina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biologicas. Centro de Investigaciones de Fitopatologia. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Centro de Investigaciones de Fitopatologia; Argentina

Alternaria alternata is recorded as the causal agent of seed discoloration of Amaranthus caudatus ssp. mantegazzianus for the first time in Argentina.