Las coníferas pueden tener daños importantes por enfermedades en vivero, entre las que destacan la pudrición de raíz y marchitez de plántulas. En Pinus spp. se les reconoce como un padecimiento en diversas regiones del mundo. Durante 2013 y 2014 se observaron tales síntomas, además de amarillamiento de plantas en estados iniciales de Pinus patula y P. pseudostrobus en un vivero forestal en el estado de Guerrero, México. Así, se propuso el presente estudio, cuyos objetivos consistieron en identificar a los hongos fitopatógenos asociados con ese problema, mediante la caracterización morfológica de las estructuras de reproducción asexual; análisis de secuencias ITS del ADNr y pruebas de patogenicidad; además de, determinar la incidencia y severidad de cada una de las especies de patógenos de interés. A partir de las plántulas con manifestaciones de daño de las dos especies de pino, se obtuvieron ejemplares aislados pertenecientes al género Fusarium. La caracterización morfológica, prueba de patogenicidad, y análisis de secuencias ITS de tales organismos evidenciaron que F. solani y F. oxysporum son las especies fúngicas responsables de ocasionar los síntomas de marchitez de plantas de Pinus. No se observó diferencia significativa entre la incidencia y la severidad de la enfermedad causada por dichos agentes.
La marchitez de plantas de estevia (Stevia rebaudiana Bertoni) es uno de los problemas fitosanitarios de mayor importancia en la zona productora de Veracruz. El objetivo de este estudio fue identificar al agente causal de los síntomas de marchitez en plantas de estevia en una plantación localizada en Martínez de la Torre, en el estado de Veracruz, México. En 2015, se observaron y recolectaron plantas de estevia con síntomas de pudrición de raíz, necrosis basal del tallo y marchitez. A partir de las muestras, se obtuvieron continuamente colonias fúngicas de Fusarium. Para la identificación del hongo, se realizó una caracterización morfológica y análisis de secuencias de la región del espaciador interno transcrito (ITS) y de la secuencia parcial del gen factor de elongación 1-alpha (EF1-α). Además, se verificó la patogenicidad de un aislado representativo de Fusarium en plantas de estevia. Los resultados de la caracterización morfológica, análisis de secuencias ITS y EF1-α, así como las pruebas de patogenicidad, determinaron que Fusarium oxysporum es el agente causal de los síntomas de marchitez de plantas de estevia en Martínez de la Torre, Veracruz.
<p><strong>Background:</strong> recently there has been concern for the monitoring of ambrosial complexes in Mexico that consist of a symbiotic relationship between a beetle and fungi, where the female invades a wide variety of species making galleries in the bark and wood, in which beetles reproduce and grow the fungi to feed the colony, these fungi can be a phytopathogen that can cause serious damage in the infected trees. The proximity of <em>Raffaelea lauricola</em> now present in Texas and the presence of <em>Fusarium euwallacea</em> in the north of Mexico; fungi that have caused great losses in the United States, put in risk the avocado production zones in Mexico. Consequently, the report of new fungi related to ambrosial complexes is of great importance. <strong>Objective:</strong> to carry out pathogenicity tests of fungi related to ambrosial complexes in avocado ‘Hass’. <strong>Methodology:</strong> Isolates of <em>Raffaelea brunnea</em>, <em>Ceratocystiopsis</em> sp. (pre-identified) and <em>Fusarium</em> sp., from avocado trees parasitized with ambrosial beetles from the state of Michoacán and an unidentified fungus from Chiapas (Mexico) were used. Artificial inoculations with the fungi were carried out by wounds in mature stem and shoots of the growth of the year (young) of ‘Hass’ plants, and the symptoms and the progress of the damage within the stem were evaluated. Three of the isolates underwent a molecular identification analysis with the complete region of the ITS internal transcript space. <strong>Results:</strong> the fungus <em>Ceratocystiopsis</em> sp. was identified as <em>Ophiostoma</em> sp. and <em>Fusarium</em> sp. such as <em>Fusarium solani</em>, both isolated from Michoacán. While the Chiapas fungus was identified belonging to the genus <em>Fusarium</em>. After inoculation<em>, R. brunnea</em> and <em>Fusarium</em> sp. stood out in pathogenicity, with greater advancement within the stem and damage that in some cases reached the pith tissue, showing leaf wilting and reddish-brown staining inside the stem. These two fungi showed differential damage progression behavior according to the type of maturity of the tissue, where <em>Fusarium</em> sp. advanced more in the young tissue and <em>R. brunnea</em> in the mature one. <strong>Implications: </strong>it is proposed to consider that the study was only carried out in ‘Hass’, thus this may be an important factor, since probably if the fungi were inoculated in more varieties, differences in behavior of the advance in damage of these could be found. <strong>Conclusions: </strong>all the fungi showed to be pathogenic with variation in severity. In terms of <em>Raffaelea brunnea</em>, a peculiar behavior was found in the severity of internal and external damage, in which external symptoms may or may not occur, strictly in ‘Hass’ avocado plants 30 days after inoculation.</p>
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