Identification of Rhizoctonia solani associated with soybean in Brazil by rDNA-ITS sequences

Abstract

The aim of this study was to identify isolates of Rhizoctonia solani causing hypocotyl rot and foliar blight in soybean (Glycine max) in Brazil by the nucleotide sequences of ITS-5.8S regions of rDNA. The 5.8S rDNA gene sequence (155 bp) was highly conserved among all isolates but differences in length and nucleotide sequence of the ITS1 and ITS2 regions were observed between soybean isolates and AG testers. The similarity of the nucleotide sequence among AG-1 IA isolates, causing foliar blight, was 95.1-100% and 98.5-100% in the ITS1 and ITS2 regions, respectively. The nucleotide sequence similarity among subgroups IA, IB and IC ranged from 84.3 to 89% in ITS1 and from 93.3 to 95.6% in ITS2. Nucleotide sequence similarity of 99.1% and 99.3-100% for ITS1 and ITS2, respectively, was observed between AG-4 soybean isolates causing hypocotyl rots and the AG-4 HGI tester. The similarity of the nucleotide sequence of the ITS-5.8S rDNA region confirmed that the R. solani Brazilian isolates causing foliar blight are AG-1 IA and isolates causing hypocotyl rot symptoms are AG-4 HGI. The ITS-5.8S rDNA sequence was not determinant for the identification of the AG-2-2 IIIB R. solani soybean isolate.

General Description of Rhizoctonia Species Complex

“…Their pathological and ecological information is less. (Baird, 1996;Holtz et al, 1996;Fenille et al, 2002;Ravanlou and Banihashemi, 2002;EI Hussieni, 2003;Kuramae et al, 2002Kuramae et al, , 2003Naito, 2004;Yang et al, 2005c).…”

Caracterização de isolados de Rhizoctonia associados à queima foliar em Roraima.

“…Há vários relatos na literatura que isolados de R. solani associada a doenças com sintoma de queima foliar em várias culturas pertencem ao grupo de anastomose AGI (PASCUAL et al, 2000;SHARMA et al, 2005). No Brasil, o subgrupo AGI-1A foi identificado em várias associações de isolados de R. solani e queima foliar em hospedeiros como a soja (FENILLE et al, 2003), feijão-caupi (NECHET; HALFELD-VIEIRA, 2006b), melancia (NECHET; HALFELD-VIEIRA, 2006a), pastagem (GONçALVES et al, 2009) e arroz (SOUZA et al, 2007. Nesse estudo identificou-se pela primeira vez um isolado de R. solani associado à mela do feijão-caupi como pertencente ao subgrupo AGI-1B e os subgrupos dos isolados obtidos de feijão-guandú e de alface, também pertencentes ao subgrupo AGI-1B.…”

“…Além de infectar vários hospedeiros, os isolados de R. solani pertencentes ao grupo AGI apresentam uma diversidade de características culturais (GARCÍA et al, 2006). O crescimento micelial e a formação de escleródios foram bastante variáveis de acordo com o isolado e o meio de cultura testado.…”

<b>Agrosilvopastoral system enhances suppressiveness to soybean damping-off caused by <i>Rhizoctonia solani</i> and alters <i>Fusarium </i>and <i>Trichoderma</i> population density

“…This pathogen causes reduction in soybean yields worldwide, at quantities up to 11.5 and 26.1 thousand metric tonnes in northern of United States and in Canada, respectively (Wrather et al, 2010;Wrather & Koenning, 2006). In Brazil, this pathogen is responsible for the pre and post-emergence damping-off and also for aerial blight of soybean (Fenille, Souza, & Kuramae, 2002). The availability of resistant cultivars is limited.…”