RESUMO O uso de gramas cultivadas no Brasil cresceu 40% entre 2010 e 2015, sendo que a espécie Zoysia japonica Steud, principalmente a cultivar ‘Esmeralda’, corresponde a 81% do mercado de gramas cultivadas no país. A doença mais importante da grama zoysia, conhecida por “large patch”, é causada por Rhizoctonia solani, ocorrendo nos gramados brasileiros especialmente nos meses de inverno. O objetivo deste trabalho foi contribuir para a identificação e caracterização do grupo de anastomose de isolados de R. solani provenientes de lesões típicas de “large patch” coletados em grama esmeralda de jardins e campos de golfe nos estados de São Paulo e Bahia, Brasil. Os 12 isolados obtidos apresentaram colônias marrom escuro, com crescimento micelial aéreo, hifas multinucleadas, e ausência de zonação concêntrica ou escleródios, bem como exibiram sua maior taxa de crescimento micelial a 25°C. Em experimentos de patogenicidade, os isolados de R. solani, com exceção de três, reduziram o crescimento das plantas de grama zoysia. Baseado na análise das sequencias da região ITS do rDNA, os isolados agruparam com isolados referências do grupo de anastomose AG 2-2 LP. Inferências filogenéticas mostraram que os isolados brasileiros estão agrupados em dois clados que compartilham o mesmo ancestral comum com 96% booststrap. Em um dos clados estão apenas isolados brasileiros e no outro estão também isolados de R. solani AG 2-2 LP americanos e japoneses. Este é o primeiro relato e caracterização de R. solani AG 2-2 LP em grama zoysia no Brasil.

ABSTRACT The use of cultivated grasses in Brazil has grown by 40% between 2010 and 2015, and the species Zoysia japonica Steud, especially the cultivar ‘Esmeralda’, corresponds to 81% of the grass market in the country. The most important disease affecting zoysia grass, known as large patch, is caused by Rhizoctonia solani and occurs in the Brazilian lawns particularly during winter months. The aim of this study was to contribute to the identification and characterization of the anastomosis group of R. solani isolates from lesions typical of large patch collected from ‘Esmeralda’ grass at gardens and golf courses in the states of São Paulo and Bahia, Brazil. All 12 obtained isolates presented dark-brown colonies with aerial mycelial growth, multinucleated hyphae and absence of concentric zonation or sclerotia, and showed their greatest mycelial growth rate at 25°C. In pathogenicity experiments, except three out of R. solani isolates, reduced the growth of zoysia grass. Based on the analysis of sequences of the rDNA-ITS region, the isolates clustered with reference isolates of the anastomosis group AG 2-2 LP. Phylogenetic inference showed that the Brazilian isolates are grouped into two clades that shared the same common ancestral with 96% bootstrap. One of the clades includes only Brazilian isolates while the other one also includes American and Japanese R. solani isolates AG 2-2 LP. This is the first report and characterization of R. solani AG 2-2 LP in zoysiagrass in Brazil.

ABSTRACT Bacterial halo blight, caused by Pseudomonas syringae pv. garcae, is an important disease of coffee crop occurring in Brazil and other countries. In recent years, outbreaks of this disease have damaged several coffee crops in Brazil. Aggressiveness and genetic diversity of 25 strains of P. s. pv. garcae, obtained between the years 1958 and 2011, in 23 cities of São Paulo and Minas Gerais states, as well as three strains from Kenya were evaluated in this study. The strains were inoculated on coffee seedlings cultivar Mundo Novo, and their genetic diversity was evaluated by ERIC-PCR, REP-PCR, and their combination. All the strains were pathogenic to the coffee seedlings; the results of pathogenicity tests, in both experiments, could be divided in four aggressiviness classes (highly aggressive; aggressive; moderately aggressive and less aggressive). The Kenyan strains grouped separately from the Brazilian strains with ERIC-PCR and the combination of ERIC- and REP-PCR. The Brazilian strains could be grouped in two sub-clusters, the first including the older strains, obtained from 1958 to 1978, and the other comprising the remaining strains. With a few exceptions, strains isolated from 1997 to 2011, grouped mainly by their region of origin, were predominantly isolated from higher altitude regions, above 800 m. This probably occurred because the climatic conditions that prevail in these regions, characterized by milder temperatures and regular rainfall, are favorable for the coffee crop and for the production of high quality coffee beverage, but can be also favorable to bacterial halo blight.