Citomorphological, cultural, molecular and pathogenical characterization of rhizoctonia solani kühn associated with rice in tocantins, Brazil
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Abstract
In Tocantins State, Northern Brazil, the incidence of Rhizoctonia sheath blight on rice is important, causing significant yield losses on rice crops under irrigation. The main objective of this research was to determine the anastomosis group (AG) of R. solani associated with rice in that area, testing the hypothesis that these isolates are from the AG-1 IA, which is also associated with the soybean leaf blight occurring i n wet ar eas of Nor t her n Br azi l . Al l t he f our r i ce i sol at es wer e char act er i zed, by hyphal f us i on, as AG-1 I A. By cul t ur al charact eri zat i on, based on basal t emperat ures for mycel i al growt h (mi ni mum, opt i mum and maxi mum), t he ri ce i sol at es had growt h profile similar to the tester isolates AG-1 IA, AG-1 IB and AG-1 IC. The rice isolates were characterized as autotrophic for thiamine, as well as the AG testers AG-1 IA, IB, IC, AG-4 HGI and the soybean leaf blight isolate SJ-047. The pathogenicity test on rice IRGA-409 and the cross pathogenicity on soybean IAC-18 (susceptible to the leaf blight disease) indicated that, besides causing sheath blight, these rice i sol at es al so cause l eaf bl i ght on soybean. Si mi l arl y, t he soybean isolates SJ-047 was pathogenic to rice. The sequences from the ITS-5.8S region of rDNA from the rice isolates were similar to sequences of AG-1 IA deposited at GenBank®-NCBI. The ITS-rDNA phylogeny indicated a common phylogenetic group formed by these rice isolates, t he i s ol at e SJ-047 and t he t es t er AG-1 I A. Thus, bas ed on cytomorphological, cultural, phylogenetics and pathogenic attributes, the hypothesis that the rice isolates of R. solani from Tocantins all belong to the AG-1 IA was confirmed, besides the indication that these isolates can also cause soybean foliar blight.
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Anastomosis groups, Cross-pathogenicity, Phylogeny, Ribossomal DNA, Soybean
Language
Portuguese
Citation
Summa Phytopathologica, v. 33, n. 2, p. 129-136, 2007.
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