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1.
Plant Dis ; 2023 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-36825318

RESUMO

Tomato (Solanum lycopersicum L.) is one of the most important crops in Mexico due to its economic and nutritional value. Among the main diseases in tomato production is Fusarium wilt, which can cause 60% production losses (Ascencio et al, 2008). Mixed infections of Fusarium species or other fungi genera, would increase disease severity. During April to May of 2021, tomato plants with more than 60 days old, were collected from the main production areas of Aguascalientes (22°03'46.5"N 102°05'17.4"W and 22°04'53.64"N 101°58'55.81"W) and Zacatecas (23°05'59.2"N 102°41'07.3"W and 22°16'52.1"N 102°00'11.8"W) Mexico states. Plants showed main root rot, vascular bundles necrosis with corky appearance, stem crown rot, and ascending yellowing. The main root and stem crown were cut in 0.25 cm2 pieces and disinfested in 2% NaClO for one minute, rinsed with distilled water two times, placed on acidified potato dextrose agar (PDA) medium, and incubated at 25 ± 2°C for 7 days. Characteristic Fusarium growths were purified by hyphal tip on PDA, subsequently pure strains were obtained by single-spore isolation method. Several fungi colonies were obtained, but we focused on the colonies that showed abundant aerial mycelium of white color and irregular growth, which turned yellowish to golden and brown color as it ages. Carnation leaf agar (CLA) medium were used for conidia and sporodochium development. Chains of terminal, intercalary and agglomerated chlamydospores with thick, rough brown walls of 18.9 (7.46) µm in diameter (n=120) were observed in the mycelium. Macroconidia with 5 to 7 septa were 30 to 75 (28.32) µm in long and 1.2 to 4.8 (3.2) µm in wide (n=72). Basal cell developed in foot-shape, apical cell was elongated and slightly curved, and some macroconidia had swollen midd-cell. Sporodochium was orange to brown in color and microconidia were absent (Figure 1). Two representative strains from each state, LCA-3.1 and EMA-1 from Aguascalientes and ECZ-4 and LRZ-6 from Zacatecas, were selected for DNA amplification of ITS, TEF-1α and RPB2 regions, with universal primers ITS1/ITS4, EF1/EF2 and 2-5F2/7cR (White et al.1990; O'Donnell et al. 1998, 2013). PCR products were sequenced by Psomagen, Inc. (USA). The sequences obtained showed 100% of similarity among themselves and within species of the Fusarium incarnatum-equiseti species complex (FIESC) with nucleotide NCBI accessions NR_121457 (Type material) for ITS and MW362069 for TEF-1α; and 99.28% with MN170399 for RPB2 in FUSARIOID-ID database. According to morphological (Leslie and Summerell, 2006) and molecular characteristics, isolates were identified as Fusarium equiseti (FIESC 14). The LCA-3.1 sequences were selected to be deposited in GenBank with accession numbers OM812801 (ITS), OM937108 (TEF-1α) and ON653596 (RPB2). Pathogenicity tests were performed twice, under greenhouse conditions in tomato seedlings of cv. Rio Grande. Five tomato seedlings were inoculated by root immersion method (Lopez et al, 2018) in a 1x106 spores/mL solution for 8 min, and transplanted to 1L pots with sterile peat. Five controls plants were immersed in sterile water. At 14 days after inoculation, a general plant decline and slower growth compared to the control plants were observed. Subsequently, plants showed root rot, vascular necrosis, and a brown ring in stem crown. Controls were symptomless. The fungi were re-isolated from symptomatic plants and were morphologically similar to the inoculated strains. Patel et al. (2017) described the pathogenic and toxic effects of F. equiseti on tomato, causing low seed germination, and low root and shoot growth. This is the first report of F. equiseti causing root and stem rot in tomato plants in Mexico.

2.
s.l; s.n; 2011.
Tese em Espanhol | Repositorio | ID: rpo-1882

RESUMO

La resistencia a los insecticidas químicos ocasionada por los insectos, ha llevado al interés en los hongos como agentes de control biológico de mosquitos. La mayoría de los trabajos con entomopatógenos se han evaluado en relación a larvas, pero hace poco se han comenzado a evaluar infecciones de mosquitos adultos a través de la exposición de superficies tratadas con conidias de hongos. En el presente estudio se evaluaron cepas mexicanas de Beauveria bassiana y Metarhizium anisopliae contra Aedes aegypti, lo que demuestra que el comportamiento de los machos impregnados con los hongos causan una mortalidad y daños en las variables de fecundidad en hembras. Todas las cepas a 6x108 conidias/ml -1 fueron altamente virulentas con una TL50 de 2.70(±0,29)-5.33(±0.53) días estimado en la exposición de hembras. Machos vírgenes de Aedes aegypti (Linneo) fueron expuestos durante 48h a la dosis de 6x108 conidias ml-1 de un aislado de Metarhizium anisopliae y luego fueron confinados con hembras vírgenes para examinar transmisión por conducta de cópula. En hembras expuestas a un macho contaminado con el aislado H-M5 hubo un 90% de mortalidad, una vida media de siete días, y fecundidad media de 0.52±0.32 huevos por hembra, la cual fue 99% más baja que la fecundidad en el control (35.35±8.3). Menos del 20% de las hembras infectadas resultaron inseminadas lo cual sugiere que la mayoría se infectaron por intentos de cópula. De la misma forma la transmisión de dos cepas de B. bassiana (H-B2 y H-B4), probadas en el apareamiento, ambos mataron entre 80-90% de las hembras en 15 días confinados con machos previamente expuestos durante 48 horas a los hongos. De las tasas de mortalidad, 27 y 48% respectivamente, fueron las infecciones adquiridas por cópulas, donde se produjo la inseminación. La TL50 para las hembras infectadas sexualmente fueron de 7.92(±0.46) y 8.82(±0.45) días para ambas cepas, mientras que el control fue de 13.92 (± 0.58). Del mismo modo, la fecundidad disminuyó entre 95% y 60% con ambos aislados en comparación con el control. El aislado H-M5 es un candidato prometedor para biocontrol vectorial del dengue, pero antes se debe estudiar el riesgo que el hongo implica para la salud pública. Para B. bassiana este es el primer reporte que se da contra Ae. aegypti a través de comportamiento de cópula de machos vírgenes hacia hembras.(AU)


Assuntos
Aedes/efectos de drogas , Metarhizium/inmunología , Beauveria/inmunología , Control de Mosquitos/métodos , Resistencia a los Insecticidas
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