RESUMEN
The rubber tree (Hevea brasiliensis) is one of the major domesticated crops planted commercially for the production of natural rubber (NR) worldwide. In recent years, rubber trees in the Southern states of India and other rubber-producing countries have experienced a severe leaf spot disease, characterized by the appearance of several brown circular spots in the initial stage, which later spread all over the lamina of fully matured leaves, leading to yellowing and defoliation. The causal organism of this Circular Leaf Spot (CLS) disease has not been conclusively identified in any previous studies. In this study, we collected infected leaf samples from various locations in the South Indian states. We aimed to identify the actual fungal pathogen that causes the CLS disease on rubber trees. Based on the morphological and molecular analysis of the most frequently isolated fungi from infected leaf samples were identified as Colletotrichum siamense and Colletotrichum fructicola. Pathogenicity tests also confirmed the involvement of isolated Colletotrichum spp. in the development of CLS disease. These findings provide valuable insights into understanding the CLS disease and its impact on rubber cultivation. To our knowledge, it is the first report of C. siamense and C. fructicola associated with CLS disease of rubber trees in India.
Asunto(s)
Colletotrichum , Hevea , Enfermedades de las Plantas , Hojas de la Planta , Hevea/microbiología , Colletotrichum/genética , Colletotrichum/aislamiento & purificación , Colletotrichum/clasificación , Enfermedades de las Plantas/microbiología , India , Hojas de la Planta/microbiología , ADN de Hongos/genética , Filogenia , Análisis de Secuencia de ADN , Datos de Secuencia MolecularRESUMEN
La enfermedad de muerte regresiva y pudrición del fuste de Pachaco (Schizolobium parahybum Vell Blake) fue detectada inicialmente 1988, matando árboles jóvenes en la zona central del Trópico Húmedo Ecuatoriano, desde entonces, cada año, miles de árboles mueren por esta causa. En el año 2002 se realizó la presente investigación que abarcó tres rodales de distintas edades, ubicados en provincias diferentes, planteándose los siguientes objetivos: describir la sintomatología de la enfermedad, su incidencia en las zonas de estudio e identificar los microorganismos asociados a árboles de S. parahybum enfermos. La enfermedad mostró una sintomatología compleja, empezando con una marchitez vascular y perdida de coloración verde oscura de las hojas hasta tornarse cloróticas. Las heridas no cicatrizadas mostraron una pudrición circular que afecta la corteza y el xilema, emanando fluidos de color amarillo claro a café oscuro, con fuerte olor a materia orgánica en descomposición. En la provincia de Los Ríos (rodal mayor a 25 años) se encontró la mayor incidencia de la enfermedad (55 por ciento), seguido de las provincias Esmeraldas (rodal de 8 años) y Santo Domingo de Los Tsáchilas (rodal de 4 años) con 29 y 24 por ciento, respectivamente. De árboles enfermos se aislaron e identificaron cinco hongos, tres a nivel de género: Macrophoma sp., Fusarium sp. y Graphium sp. y dos a nivel de especies: Ceratocystis paradoxa (Dade) y C. moniliformis (Hedgc.). Las pruebas de patogenicidad demostraron que C. paradoxa, Macrophoma sp. y C. moniliformis provocaron los mayores valores de volumen aparente de necrosis con 5.40, 3.55 y 3.48 cm3respectivamente.
Dieback disease and stem rot of Pachaco (Schizolobium parahybum Vell Blake) was detected initially in 1988, killing young trees in the Ecuadorian Humed Tropics, since then, thousands of trees are dying annually. The present investigation was made in 2002, where were included three rodales of different ages, located in different provinces. The aim for this research was describe the symptoms its incidence in the zones of study and identifying the associated microorganisms affecting S. parahybum. The disease showed complex symtoms, beginning with a wither of dark, green coloration of the leaves until becoming clorotics. The healed wounds did not show a circular root that affects the crust and xylem, of where emanates fluid of clear yellow color to dark coffee, with strong smell to organic matter in decomposition. In Los Ríos province (rodal more than 25 years old) the greater incidence of the disease was 55 percent, followed by he provinces of Esmeraldas (rodal of 8 years old) and Santo Domingo de Los Tsáchilas (rodal of 4 years old) with 29 and 24 percent respectively. Of ill trees five fungi isolated themselves and identified, three at sort level: Macrophoma sp., Fusarium sp. and Graphium sp. and two at level of species: Ceratocystis paradoxa (Dade) and C. Moniliformis (Hedgc.). The pathogenicity tests demonstrated that C. paradoxa, Macrophoma sp. and C. moniliformis caused the higher values of apparent volume of necrosis with 5.40, 3.55 and 3.48 cm3 respectively.