Patogenicidad de Phytophthora cinnamomi RANDS en ciprés de la cordillera (Austrocedrus chilensis) y estudios preliminares de hongos antagonistas.
Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
El género Phytophthora es responsable de algunas de las epidemias más destructivas a nivel mundial. Entre las especies más importantes de este género se encuentra Phytophthora cinnamomi, patógeno que puede provocar importantes impactos ecológicos y pérdidas económicas en ecosistemas forestales, debido a su amplia distribución geográfica y comportamiento polífago. En Chile, el patógeno se ha detectado en plantaciones comerciales de paltos y castaños, y en los últimos años afectando especies nativas, como son araucaria, coigüe, canelo, y recientemente detectado en Austrocedrus chilensis (ciprés de la cordillera), aunque para esta especie aún no se ha comprobado la patogenicidad de P. cinnamomi. El ciprés de la cordillera posee una gran plasticidad ecológica, presentándose en bosques puros o mixtos junto con especies del género Nothofagus, siendo algunas de estas especies con demostrada susceptibilidad a P. cinnamomi. La diseminación P. cinnamomi dentro de bosques mixtos podría aumentar la posibilidad de infección hacia árboles de A. chilensis. El control de especies de Phytophthora en cultivos comerciales se ha basado en el manejo cultural y uso de fungicidas específicos, no obstante, aplicaciones frecuentes de estos productos podrían generar poblaciones resistentes del patógeno. Por otro lado, en ecosistemas forestales nativos no parece viable la aplicación de fungicidas, surgiendo como alternativa la utilización del control biológico. El objetivo de este estudio fue verificar la patogenicidad de aislados de P. cinnamomi sobre A. chilensis y determinar el efecto antagónico de cepas de hongos sobre P. cinnamomi. Los aislados de P. cinnamomi fueron obtenidos desde la rizosfera de árboles de ciprés de la cordillera y de otras especies nativas que presentaban síntomas atribuibles al patógeno. Los ensayos de patogenicidad se realizaron en plantas de ciprés de la cordillera de dos años, empleando los métodos de infestación de substrato, evaluándose mortalidad de plantas y síntomas en follaje y raíces, e inoculación en tallosiguiendo un diseño factorial 5x2x5, y evaluándose síntomas y tamaño de lesión ocasionado. Para las pruebas de antagonismo in vitro fueron utilizadas aislados de Trichoderma y Clonostachys, proporcionados por el Laboratorio de Patología Forestal. Los ensayos consistieron en pareamientos en medios de cultivo, entre los aislados de hongos y de P. cinnamomi, siguiendo un diseño factorial 4x13x4 y evaluándose la inhibición del crecimiento de la colonia, parasitismo de hifas, antibiosis y lisis de hifas de P. cinnamomi.
Los ensayos de patogenicidad en sustrato mostraron distintos grados de agresividad de P. cinnamomi en plantas de A. chilensis. El aislado D-17 a las 12 semanas fue el único en causar la muerte de las plantas, logrando ser reaislado en un 38%.
Por otro lado, los ensayos in vitro, demostraron distintos mecanismos de acción por parte de los antagonistas probados, logrando inhibir entre un 57%-95% el crecimiento micelial de P. cinnamomi.
The genus Phytophthora is responsible for some of the most destructive epidemics worldwide. Among the most important species within this genus is Phytophthora cinnamomi, a pathogen capable of causing significant ecological impacts and economic losses in forest ecosystems due to its wide geographic distribution and polyphagous behavior. In Chile, this pathogen has been detected in commercial plantations of avocado and chestnut, and in recent years it has also affected native species such as Araucaria, Nothofagus dombeyi (coigüe), Drimys winteri (canelo), and it has been recently detected in Austrocedrus chilensis (cordilleran cypress). However, for this latter species, the pathogenicity of P. cinnamomi has not yet been confirmed. Austrocedrus chilensis exhibits high ecological plasticity, occurring in pure or mixed forests together with species of the genus Nothofagus, some of which have demonstrated susceptibility to P. cinnamomi. The spread of P. cinnamomi within mixed forests could increase the likelihood of infection of A. chilensis trees. Control of Phytophthora species in commercial crops has relied on cultural management practices and the use of specific fungicides; however, frequent applications of these products may lead to the development of resistant pathogen populations. In contrast, the application of fungicides does not appear to be feasible in native forest ecosystems, making biological control a potential alternative. The objective of this study was to verify the pathogenicity of P. cinnamomi isolates on A. chilensis and to determine the antagonistic effect of fungal strains against P. cinnamomi. The P. cinnamomi isolates were obtained from the rhizosphere of cordilleran cypress trees and other native species showing symptoms attributable to the pathogen. Pathogenicity assays were conducted on two-year-old cordilleran cypress plants using substrate infestation methods, evaluating plant mortality and foliar and root symptoms, as well as stem inoculation following a 5 × 2 × 5 factorial design, assessing symptom development and lesion size. For in vitro antagonism assays, isolates of Trichoderma and Clonostachys, provided by the Forest Pathology Laboratory, were used. These assays consisted of dual cultures on growth media between fungal isolates and P. cinnamomi, following a 4 × 13 × 4 factorial design, and evaluating inhibition of colony growth, hyphal parasitism, antibiosis, and hyphal lysis of P. cinnamomi. Substrate pathogenicity assays showed different degrees of aggressiveness of P. cinnamomi on A. chilensis plants. At 12 weeks, isolate D-17 was the only one that caused plant death, and it was successfully reisolated in 38% of cases. In contrast, in vitro assays demonstrated different mechanisms of action by the antagonists tested, achieving inhibition of P. cinnamomi mycelial growth ranging from 57% to 95%.
The genus Phytophthora is responsible for some of the most destructive epidemics worldwide. Among the most important species within this genus is Phytophthora cinnamomi, a pathogen capable of causing significant ecological impacts and economic losses in forest ecosystems due to its wide geographic distribution and polyphagous behavior. In Chile, this pathogen has been detected in commercial plantations of avocado and chestnut, and in recent years it has also affected native species such as Araucaria, Nothofagus dombeyi (coigüe), Drimys winteri (canelo), and it has been recently detected in Austrocedrus chilensis (cordilleran cypress). However, for this latter species, the pathogenicity of P. cinnamomi has not yet been confirmed. Austrocedrus chilensis exhibits high ecological plasticity, occurring in pure or mixed forests together with species of the genus Nothofagus, some of which have demonstrated susceptibility to P. cinnamomi. The spread of P. cinnamomi within mixed forests could increase the likelihood of infection of A. chilensis trees. Control of Phytophthora species in commercial crops has relied on cultural management practices and the use of specific fungicides; however, frequent applications of these products may lead to the development of resistant pathogen populations. In contrast, the application of fungicides does not appear to be feasible in native forest ecosystems, making biological control a potential alternative. The objective of this study was to verify the pathogenicity of P. cinnamomi isolates on A. chilensis and to determine the antagonistic effect of fungal strains against P. cinnamomi. The P. cinnamomi isolates were obtained from the rhizosphere of cordilleran cypress trees and other native species showing symptoms attributable to the pathogen. Pathogenicity assays were conducted on two-year-old cordilleran cypress plants using substrate infestation methods, evaluating plant mortality and foliar and root symptoms, as well as stem inoculation following a 5 × 2 × 5 factorial design, assessing symptom development and lesion size. For in vitro antagonism assays, isolates of Trichoderma and Clonostachys, provided by the Forest Pathology Laboratory, were used. These assays consisted of dual cultures on growth media between fungal isolates and P. cinnamomi, following a 4 × 13 × 4 factorial design, and evaluating inhibition of colony growth, hyphal parasitism, antibiosis, and hyphal lysis of P. cinnamomi. Substrate pathogenicity assays showed different degrees of aggressiveness of P. cinnamomi on A. chilensis plants. At 12 weeks, isolate D-17 was the only one that caused plant death, and it was successfully reisolated in 38% of cases. In contrast, in vitro assays demonstrated different mechanisms of action by the antagonists tested, achieving inhibition of P. cinnamomi mycelial growth ranging from 57% to 95%.
Description
Tesis presentada para optar al grado de Magíster en Ciencias Forestales.
Keywords
Phytophthora cinnamoni Control, Ciprés de la cordillera, Hongos, Bosque nativo