Rhizoctonia solani AG-1 IA infects both rice and signalgrass in the Colombian Llanos

Lina Maria Ramos-Molina,Edisson Chavarro-Mesa,Danilo Augusto Dos Santos Pereira,Paulo Cezar Ceresini,María Del Rosario Silva-Herrera

doi:10.1590/1983-40632016v4638696

Lina Maria Ramos-Molina, Edisson Chavarro-Mesa + Show 3 more

Open Access

https://doi.org/10.1590/1983-40632016v4638696

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Abstract

ABSTRACT Foliar blight and death of signalgrass (Urochloa spp.) pastures are caused by the Rhizoctonia solani fungus. This study aimed at determining which pathogens from the Rhizoctonia species complex are associated with leaf and sheath blight in Urochloa and rice, in the Colombian Llanos. Sympatric areas of Urochloa pastures adjacent to rice cropping areas were sampled using a linear transect system. The pathogens were identified using morphological traits, molecular detection based on specific primers and sequencing of the ITS-5.8S rDNA region. R. solani AG-1 IA predominated as the pathogen associated with foliar blight in all samples from U. brizantha cv. 'Toledo' and hybrid Urochloa cv. 'Mulato'. Besides R. solani AG-1 IA (18 % of the samples), Rhizoctonia oryzae-sativae (71 %) and Sclerotium hydrophilum (11 %) were also detected. In the cross-pathogenicity test, the R. solani AG-1 IA fungus was the most aggressive to Urochloa, while R. oryzae-sativae produced very mild infection symptoms. This is the first report of R. oryzae-sativae and S. hydrophilum associated with the complex of rice sheath blight diseases in Colombia.

Highlights

Signalgrass (Urochloa spp.) foliar blight and collar rot diseases are caused by the Basidiomycetes Rhizoctonia solani fungus, which emerged early in 1990 as an important pathogen for Urochloa pastures in the eastern Colombian Llanos (Ciat 1993, Argel et al 2005, Alvarez et al 2013)
A similar report was made by Alvarez et al (2013), who found that R. solani AG-1 IA was the predominant pathogen associated with foliar blight in U. brizantha, U. brizantha cv
The predominance of R. oryzae-sativae in the two rice sampling areas in the Colombian Llanos (71 % of the population sampling) is important for disease management, since R. solani AG-1 IA was considered the predominant pathogen in rice fields (Pabón Guerrero 1994)

Summary

Introduction

Signalgrass (Urochloa spp.) foliar blight and collar rot diseases are caused by the Basidiomycetes Rhizoctonia solani (sexual stage Thanatephorus cucumeris) fungus, which emerged early in 1990 as an important pathogen for Urochloa pastures in the eastern Colombian Llanos (Ciat 1993, Argel et al 2005, Alvarez et al 2013). It is possible that different pathogens from the Rhizoctonia complex could be associated with foliar blight and death of Urochloa in the Colombian Llanos, especially in areas close to rice fields. This study aimed at determining which pathogens from the Rhizoctonia species complex are associated with foliar and sheath blight in Urochloa spp. and rice, in the Colombian Llanos.

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