Soybean fungal soil-borne diseases: a parameter for measuring the effect of agricultural intensification on soil health.

The aim of this study was to investigate the influence of agricultural intensification on soil microbial diversity, chemical and physical parameters, and the decrease of the incidence of sudden death syndrome (Fusarium crassistipitatum) and charcoal rot (Macrophomina phaseolina) in soybean. Soils under different management systems were evaluated during 2 crop cycles: soybean monoculture for 24 and 11 years, soybean-maize rotation for 15 and 4 years, 1 year of soybean, and native vegetation. The incidence of both soil-borne diseases was higher under monoculture than under rotation. Increased populations of potential biocontrol agents (Trichoderma spp., Gliocladium spp., fluorescent pseudomonads) were associated with rotation treatments, especially in 2010-2011. The comparison of agricultural vs. native vegetation soil and the average of agricultural cycles showed that microbial biomass carbon and glomalin-related soil protein were higher in the rotation system than in monoculture (50% and 77%, respectively). Furthermore, from the community-level functional diversity (Biolog Eco plates), McIntosh index showed lower functional diversity in monoculture than in rotation and native vegetation plots. Agricultural intensification reduced microbial biomass carbon, glomalin-related soil protein, organic matter, total nitrogen, aggregate stability, and yield, and increased bulk density. Soil quality degradation was associated with the establishment of soil-borne pathogens and increased soybean plant susceptibility to disease.

First Molecular Detection of Ramularia Leaf Spot (Ramularia collo-cygni) in Seeds and Leaves of Barley in Argentina.

The fungus Ramularia collo-cygni B. Sutton & J. M. Waller (Rcc) was identified as the causal agent of this emerging disease on barley (Hordeum vulgare L.) based on symptoms and signs on leaves and attributes of the fungus. The common name given to the disease was "necrotic sprinkling." This disease was found for the first time on barley in fields of Buenos Aires Province, Argentina, in 2001, with severities ranging from 60 to 100% (2). During the spring of 2012, the disease spread throughout most barley growing areas of the Pampean region, affecting almost all varieties of barley in the Buenos Aires, Entre Ríos, and Santa Fe provinces. The disease showed typical symptoms of small, brown spots on leaves, sheaths, and awns, and caused rapid loss of green leaf area and significant economic damage. The diagnosis of this disease is difficult by conventional techniques and has caused some confusion. In order to obtain appropriate information about the incidence of this pathogen in the most important barley growing region of Argentina, as well as to confirm its presence on seed, 39 seed samples containing 200 seeds each and eight leaf samples were analyzed using a real-time PCR diagnostic test (4). Thirty-five of the 37 seed samples had Rcc DNA levels above the minimum detection level (0.13 pg DNA). Ramularia has been described as a seedborne fungus previously (1) and seed infection could hasten the spread of the fungus to new geographically distinct areas. Moreover, leaf samples were microscopically assessed for conidophore presence and then ground for DNA extraction. Rcc DNA was detected by PCR in all eight leaf samples. To our knowledge, this is the first report about molecular detection of R. collo-cygni in barley seed of harvested samples from Argentina. Seeds infected/infested may also lead to new strains of the fungus arriving in barley fields and provide a source of inoculum for future epidemics (3). References: (1) N. D. Havis et al. FEMS Microbiol. Lett. 256:217, 2006. (2) M. Khier et al. Salpicado necrótico, nueva enfermedad de la cebada en Argentina causada por Ramularia collo-cygni. Page 47 in: Resúmenes XI Jornadas Fitosanitarias Argentinas, 26-29 June 2002, Río Cuarto, Córdoba, 2002. (3) P. Matusinsky et al. J. Plant Pathol. 3:679, 2011. (4) J. M. G. Taylor et al. Lett. Appl. Microbiol. 50:493, 2010.

Evaluation of indigenous bacterial strains for biocontrol of the frogeye leaf spot of soya bean caused by Cercospora sojina.

AIMS: Assessment of biological control of Cercospora sojina, causal agent of frogeye leaf spot (FLS) of soya bean, using three indigenous bacterial strains, BNM297 (Pseudomonas fluorescens), BNM340 and BNM122 (Bacillus amyloliquefaciens). METHODS AND RESULTS: From cultures of each bacterial strain, cell suspensions and cell-free supernatants were obtained and assayed to determine their antifungal activity against C. sojina. Both mycelial growth and spore germination in vitro were more strongly inhibited by bacterial cell suspensions than by cell-free supernatants. The Bacillus strains BNM122 and BNM340 inhibited the fungal growth to a similar degree (I ≈ 52-53%), while cells from P. fluorescens BNM297 caused a lesser reduction (I ≈ 32-34%) in the fungus colony diameter. The foliar application of the two Bacillus strains on soya bean seedlings, under greenhouse conditions, significantly reduced the disease severity with respect to control soya bean seedlings and those sprayed with BNM297. This last bacterial strain was not effective in controlling FLS in vivo. CONCLUSIONS: Our data demonstrate that the application of antagonistic bacteria may be a promising and environmentally friendly alternative to control the FLS of soya bean. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of biological control of C. sojina by using native Bacillus strains.

First Report of Sexual Reproduction by the Soybean Sudden Death Syndrome Pathogen Fusarium tucumaniae in Nature.

Of the four fusaria that have been shown to cause soybean sudden death syndrome (SDS), field surveys indicate that Fusarium tucumaniae is the most important and genetically diverse SDS pathogen in Argentina. Although none of the SDS fusaria have been shown to produce perithecia in nature, a heterothallic sexual cycle has been demonstrated for F. tucumaniae via laboratory crosses. Herein we report on the discovery of perithecia of F. tucumaniae on soybean in Argentina. Ascospores derived from these perithecia gave rise to colonies that produced sporodochial conidia diagnostic of F. tucumaniae. Sporodochial conidia were longer and narrower than those produced by the other SDS fusaria; these conidia also possessed a diagnostic acuate apical cell and a distinctly foot-shaped basal cell. Sixteen strains derived from single ascospores subjected to a validated multilocus genotyping assay (MLGT) for SDS species determination, together with 16 conidial isolates from two sites where teleomorphs were collected, independently confirmed the morphological identification as F. tucumaniae. This study represents the first authentic report of sexual reproduction by a soybean SDS pathogen in nature.

Oral yeast carriage in HIV-infected and non-infected populations in Rosario, Argentina.

The objectives of the present study were: (i) to assess the frequency of oral colonisation by Candida species in HIV-positive patients and to compare it with a population of HIV-negative individuals, (ii) to determine the prevalence of C. dubliniensis in both populations and (iii) to determine the susceptibility of C. dubliniensis and other Candida species isolated from HIV-positive patients to the most commonly used antifungal agents. Oral samples were obtained from 101 HIV-positive and 108 HIV-negative subjects. For yeast identification, we used morphology in cornmeal agar, the API 20C Aux, growth at 45 degrees C, d-xylose assimilation, morphology in sunflower seed agar and PCR. The frequency of isolation of Candida in HIV-positive patients was: C. albicans, 60.7%; C. dubliniensis, 20.2%; C. glabrata, 5.6%; C. krusei, 5.6%; C. tropicalis, 4.5%; others, <5%. The frequency of isolation of Candida in HIV-negative patients was: C. albicans, 73.9%; C. tropicalis, 15.5%; C. dubliniensis, 2.1%; C. glabrata, 2.1%; C. parapsilosis, 2.1%; others, <5%. The oral colonisation by yeast in the HIV-positive patients was higher than that in the HIV-negative subjects. The susceptibilities of 42 Candida isolates to three antifungal agents were determined. All isolates of C. dubliniensis were susceptible to fluconazole, although several individuals had been previously treated with this drug. Out of the 42 Candida isolates, 10 presented resistance to fluconazole and 10 to itraconazole. The presence of Candida species, resistant to commonly used antifungal agents, represents a potential risk in immunocompromised patients.

Microbiological study of external otitis in Rosario City, Argentina.

Mycological and/or bacteriological studies were performed on 294 samples isolated from the external auditory control (EAC). It was observed that 185 (81.5%) of the mycological analysis were negative while 42 (18.5%) were positive with the following distribution: 22 Candida (9.7%), 15 Aspergillus (6.5%) and five associations of Aspergillus and Candida (2.2%). The bacteriological studies were negative in 52 cases (23.6%) and the frequency of the bacterial agents (75.5%) isolated were as follows: 41 Pseudomonas aeruginosa (18.6%), 24 Proteus mirabilis (10.9%), 24 Staphylococcus aureus (10.9%), and three associations of Ps. aeruginosa and Pr. mirabilis (1.4%). Pseudomonas aeruginosa, which was the most frequent bacterial species isolated, did not present associations with any fungus.

Paracoccidioidomycosis and larynx carcinoma.

Report of a case of paracoccidioidomycosis associated with a carcinoma: both located in the larynx in a patient whose therapeutic response to antifungal treatment produced a recovery of physical conditions. This case shows the importance of taking into account the diagnosis of paracoccidioidomycosis in all patients with problems in the larynx, especially those who inhabit or inhabited endemic areas of Paracoccidioides brasiliensis.

Manifestaciones cutáneas de histoplasmosis diseminada en pacientes infectados con el virus de inmunodeficiencia humana / Cutaneous manifestations of disseminated histoplasmosis in VIH infected patients

El objetivo de este trabajo es dar a conocer la frecuencia de lesiones cutáneas de histoplasmosis diseminada (HD) en pacientes con SIDA en nuestro medio, las características clínicas, métodos diagnósticos empleados y resultados terapéuticos de los casos clínicos considerados. De los 24 casos de histoplasmosis diagnosticada, 13 pacientes (54,16 por ciento), presentaron lesiones cutáneas, donde se demostró la presencia de Histoplasma capsulatum, observándose pápulas eritematoescamosas y úlceras. La correcta escarificación de dichas lesiones permitió realizar coloraciones y cultivos, que tuvieron una gran sensibilidad para detectar esta micosis. Así, del total de 13 pacientes con lesiones cutáneas, a 11 se les realizó el diagnóstico de histoplasmosis diseminada por ese método, cuando los otros materiales analizados en esos pacientes fueron negativos. Tratamiento: los 3 pacientes tratados con anfotericina B y el paciente tratado con fluconazol (F), tuvieron buena respuesta, los 7 pacientes que recibieron itraconazol: 6 presentaron buena respuesta, con un fracaso terapéutico que responde favorablemente al utilizar anfotericina B

Manifestaciones cutáneas de histoplasmosis diseminada en pacientes infectados con el virus de inmunodeficiencia humana / Cutaneous manifestations of disseminated histoplasmosis in VIH infected patients

El objetivo de este trabajo es dar a conocer la frecuencia de lesiones cutáneas de histoplasmosis diseminada (HD) en pacientes con SIDA en nuestro medio, las características clínicas, métodos diagnósticos empleados y resultados terapéuticos de los casos clínicos considerados. De los 24 casos de histoplasmosis diagnosticada, 13 pacientes (54,16 por ciento), presentaron lesiones cutáneas, donde se demostró la presencia de Histoplasma capsulatum, observándose pápulas eritematoescamosas y úlceras. La correcta escarificación de dichas lesiones permitió realizar coloraciones y cultivos, que tuvieron una gran sensibilidad para detectar esta micosis. Así, del total de 13 pacientes con lesiones cutáneas, a 11 se les realizó el diagnóstico de histoplasmosis diseminada por ese método, cuando los otros materiales analizados en esos pacientes fueron negativos. Tratamiento: los 3 pacientes tratados con anfotericina B y el paciente tratado con fluconazol (F), tuvieron buena respuesta, los 7 pacientes que recibieron itraconazol: 6 presentaron buena respuesta, con un fracaso terapéutico que responde favorablemente al utilizar anfotericina B (AU)

[Mycological study of 100 cases of ungual lesions of Rosario city (Republica Argentina)]. / Estudio micológico de 100 casos de lesiones ungueales de la ciudad de Rosario-República Argentina.

The aim of present work was to analyze several diagnostic methods of nail infections relating to various etiological agents with the different types of lesions and their probable predisposing causes. One hundred nail samples were studied including the following laboratory test: Direct microscopic exams with 40% KOH, direct exams in fluorescence microscope with calcoflúor white and mycological cultures. One or more of these methods gave positive results in 65% of the samples tested. The fungi isolated by culture were the following: Candida (predominantly non-albicans, which appeared in 70.8% of the cases), dermatophytes (25% of the cases) and opportunistic fungi (4.2%). Females showed a higher incidence of fungal infection. Candida were more frequent in finger nails, while dermatophytes occurred mainly in toe nails. The clinical characteristic of the lesions produced by Candida were: tricophytoid type (67%) and periungeal type (33%). On the other hand, dermatophytes and opportunistic fungi produced distal subungual type lesions. Since correlation between direct examination and cultures is not always found in mycological studies, based in our present results we suggest that, although they must always be carried out, both should be repeated with the addition of direct examination with calcoflúor in the cases in which the diagnosis is difficult.

Mycotic keratitis caused by Curvularia lunata var. aeria.

A mycotic keratitis case which was caused by Curvularia lunata var. aeria in a patient with an injury in the eye is described. The diagnosis was based on the mycologic analysis of several samples taken from the ulcer of cornea. In vitro tests of the sensitivity of the isolated species to several antifungal drugs were made. The results were related to the response in vivo to the treatment.