Marília Lazarotto

First Report of Ilyonectria robusta Associated with Black Foot Disease of Grapevine in Southern Brazil

In August 2012, symptoms of black foot disease were observed on 21-year-old grapevines (Vitis labrusca cv. Bordô; own-rooted cultivar) at Nova Pádua city, Rio Grande do Sul state, Brazil. Symptomatic plants showed reduced vigor, vascular lesions, decline and death of vines, and necrotic lesions on roots. Isolation of fungi associated with necrotic root tissue was made on potato dextrose agar (PDA) medium containing 0.5 g L-1 streptomycin sulfate. Cultures were incubated at 25°C for 7 days in darkness, and single-spore cultures were obtained from the colonies emerging from the diseased tissue. For morphological characterization, cultures were transferred to PDA and spezieller nährstoffarmer agar (SNA) medium with addition of two pieces of 1 cm2 filter paper. One representative isolate (Cy9UFSM) was used for morphological and molecular characterization and pathogenicity confirmation. After 10 days growth on PDA at 20°C in the dark, colonies were umber to chestnut in color (3), appeared cottony to felty in texture, and sporulated profusely. After 5 weeks on SNA and under dark conditions at 20°C, cultures formed macroconidia predominantly on simple conidiophores, 1 to 3 septate, with both ends slightly rounded. Macroconidia varied in size depending on the number of cells as follows: one-septate (23-) 27.7 (-31) × (4.5-) 5.8 (-7) μm; two-septate (26-) 30.1 (-34) × (5-) 5.6 (-6) μm; and three-septate (24-) 31.2 (-35) × (5-) 5.8 (-6.5) μm. Microconidia were observed and did not have a visible hilum (6-) 11.2 (-17) × (3.5-) 4.2 (-5) μm (n = 30 observations per structure). Brown, thick-walled globose to subglobose chlamydospores were produced abundantly on PDA, (8.5-) 13.8 (-17) μm. To confirm the species, primer pairs H3-1a and H3-1b (2) were used to amplify a portion the histone H3 gene. Sequence of this region showed 98% similarity with a reference sequence for Ilyonectria robusta (A.A. Hildebr.) A. Cabral & Crous (GenBank Accession No. JF735530). Thus, both morphological and molecular criteria supported identification of the strain as I. robusta. This isolate was deposited in GenBank as accession KF633172. To confirm pathogenicity, 4-month-old rooted cuttings of Vitis labrusca cv. Bordô were inoculated by immersing roots in a conidial suspension (106 ml-1) for 60 min. After inoculation, the cuttings were planted in 1-L bags containing commercial substrate (MecPlant). Thirty days later, each plant was re-inoculated by applying 40 ml of a conidial suspension (106 ml-1) to the commercial substrate. Ten single-vine replicates were used for each isolate, and 10 water-inoculated vines were included as controls. After 4 months, the inoculated plants showed a 22.5% reduction of root mass, with root and crown necrosis, browning of vessels, and 20% mortality. Control plants treated with water remained symptomless. The fungus was re-isolated from blackened tissue of wood from the basal end of rooted cuttings, thereby satisfying Kochs postulates. I. robusta was first associated with black foot disease of grapevine in Portugal in 2012 (1). To our knowledge, this is the first report in southern Brazil of I. robusta associated with black foot disease of grapevine. References: (1) A. Cabral et al. Mycol. Prog. 11:655, 2012. (2) N. L. Glass et al. Appl. Environ. Microbiol. 61:1323, 1995. (3) R. W. Rayner. A mycological colour chart. Commonwealth Mycological Institute and British Mycological Society, 1970.

Primeiro relato de oídio em Sesbania punicea Benth (Cav.) no Brasil

1Universidade Federal do Rio Grande do Sul, Faculdade de Agronomia, Departamento de Horticultura e Silvicultura. Porto Alegre, RS Brasil. 2Instituto Biológico de São Paulo, Avenida Conselheiro Rodrigues Alves, no 1.252, CEP 04014-002 São Paulo, SP, Brazil. Autor para correspondência: Gislaine Taís Grzeça (gis_tais@hotmail.com) Data de chegada: 27/03/2017. Aceito para publicação em: 10/11/2017. 10.1590/0100-5405/177610

Resistance of TiO2-treated Eucalyptus botryoides Wood to the Fungus Ganoderma applanatum

The aim of the present study is to investigate the resistance of Eucalyptus botryoides treated with TiO2 particles to attack by the fungus Ganoderma applanatum. The Bethel treatment method was applied to wood specimens (25 × 25 × 9 mm) and compared to CCB. The wood was subjected to the accelerated decay test and characterized through Rockwell Hardness and Fourier Transform Infrared Spectroscopy (FT-IR). The TiO2-treated wood showed lower degradation and greater resistance to the penetration of a steel sphere (Rockwell Hardness) than the untreated wood. In addition, the results of the TiO2 treatment were statistically equal to those of CCB. The FT-IR analysis showed that the fungus degraded lignin and hemicellulose in untreated samples. The present results showed the TiO2 efficiency in forming a protective layer on the cell wall and in preventing the development of microorganisms, a fact that verifies its fungicidal action on wood.

Susceptibility of Clonal Seedlings of Eucalyptus spp. to Powdery Mildew Disease

Powdery mildew is one of the main diseases in eucalyptus clonal nursery. The present work aimed to confirm the identity of the causal agent of powdery mildew in clonal seedlings of Eucalyptus spp., and to evaluate the susceptibility reaction of clones to this disease. Conidia were collected in minigardens for molecular identification of the pathogen. We assessed susceptibility by testing 4 clones: Clone 1 (Eucalyptus benthamii), Clone 2 (E. dunni), Clone 3 (E. benthamii) and Clone 4 (E. urophylla x E. globulus). Scale of classes was used for calculations of Disease Index (DI) and Final Incidence (I). Temporal analysis was performed using the Logistic and Gompertz models. The molecular identification confirmed the identity of the isolates approximate to Podosphaera pannosa (teleomorphic phase of Oidium eucalypti). The Gompertz model obtained a better adjustment to the severity and incidence data, and clones 1 and 2 showed greater susceptibility to eucalyptus powdery mildew.

Resistência biológica e colorimetria da madeira termorretificada de duas espécies de eucalípto

Os objetivos deste estudo foram os seguintes: a) observar o efeito de termorretificacao sobre a durabilidade natural da madeira de Eucalyptus tereticornis e Corymbia citriodora apos ataque de fungos causadores de podridao-branca (Trametes versicolor eGanoderma applanatum); b) avaliar parâmetros colorimetricos apos a submissao das madeiras a tratamentos termicos e aos fungos T. versicolor e G. applanatum. Para realizacao do estudo, corpos de prova de ambas as especies foram submetidos aos tratamentos: T1 - testemunha; T2 - autoclave (120 °C) a 1,5 kgf/cm2 durante 1 h; T3 - estufa laboratorial (180 °C) por 4 h; e T4 - termico combinado [120 °C (1 h) + 180 °C (4 h)]. Posteriormente, os corpos de prova foram submetidos ao apodrecimento acelerado, sendo expostos as duas especies de fungos por 16 semanas. Apos esse periodo, foram avaliadas a perda de massa e as variaveis colorimetricas, atraves dos parâmetros L*, a*, b*, C* e ho antes e depois do ataque pelos fungos. De acordo com os resultados, E. tereticornis e C. citriodora foram classificados como altamente resistentes a fungos apodrecedores, exceto no tratamento testemunha de C. citriodora submetido ao ataque de G. applanatum, o qual foi classificado como resistente. Com os tratamentos T3 e T4, a perda de massa foi reduzida em ambas as especies de madeira. As maiores mudancas nos parâmetros colorimetricos ocorreram devido ao tratamento termico e a pouca variacao observada com o ataque dos fungos apodrecedores. Houve reducao da variavel claridade (L*) e queda das matrizes vermelho (a*) e amarelo (b*), razao por que o tratamento termico mostrou-se como alternativa para protecao e escurecimento da madeira de eucalipto, tornando-a mais proxima de padroes de coloracao de madeiras nobres.

Identificação de Fungos Emboloradores em Madeira de Pinus spp. em Laboratório

The objective of this study was to identify the species of mold fungi in untreated wood of Pinus spp. stored at laboratory conditions in Pelotas, Rio Grande do Sul, Brazil. For this purpose, 10 Pinus spp. wood samples were randomly selected for fungal structures identification by morphological spores and subsequently, these were isolated and sent elongation factor 1-alpha (EF-1α) sequencing for molecular identification. Five isolates were obtained from the genus Trichoderma and one isolate of Fusarium. These were identified by molecular analysis as belonging to the species T. atroviride and F. solani, respectively.