Rosa Maria Valdebenito Sanhueza

Epidemiology of apple leaf spot

A mancha foliar da macieira (Malus domestica), causada por Colletotrichum spp., e uma das principais doencas da macieira no Sul do Brasil. Estudos sobre sua epidemiologia foram conduzidos em Passo Fundo e Vacaria, RS, no periodo de fevereiro/1998 a outubro/2000. A doenca foi encontrada nos seis pomares amostrados em 1998 e 1999. Isolados do fungo obtidos a partir de lesoes em folhas e frutos corresponderam as especies C. gloeosporioides (75%), C. acutatum (8%) e Colletotrichum sp. (17%). O patogeno sobreviveu em ramos e gemas dormentes, mas nao em folhas caidas ao solo e frutos mumificados. O tratamento de inverno com duas aplicacoes de oxycloreto de cobre (0,3%) reduziu o inoculo do patogeno em gemas (65 a 84,6%) e ramos (85,6 a 93,7%), mas nao diminuiu o progresso inicial da doenca. A severidade da mancha foliar da macieira aumentou a medida que a temperatura ambiente foi elevada de 14 para 26-28 °C. A 34 °C, entretanto, a infeccao foi completamente inibida. A duracao do molhamento foliar requerido para infeccao variou de duas horas a 30 °C para 32 h a 16 °C. A relacao da temperatura (T) e do molhamento foliar (W) com a severidade de doenca (Y) foi representada pela equacao Y = 0,00145[((T-13)1,78)((34,01-T )1,09)] * 25/[1+14 exp(-0,137W)], R2 = 0,73 e P < 0,0001. Atualmente, estas informacoes estao sendo utilizadas para manejo da mancha foliar da macieira e para validacao de um sistema para sua previsao.

Controle em pós-colheita de Monilinia fructicola em pêssegos

The Brown rot (Monilinia fructicola) causes economic losses for peach (Prunus persicae) producers in spite of sanitation and pre and post-harvest chemicals. There have been several researches on biological control as an desirable alternative for controling plant diseases. We screened putative antagonists of Monilinia fructicola and also evaluated the efficiency of fungicides and biological controls in reducing post-harvest diseases. In the laboratory, the antagonistic potential of filamentous fungi obtained from peaches from the region of Lapa, PR, was evaluated using two methods: pairing culture and diffusion of products per membrane. Two experiments were conducted after growing seasons of 1997 and 1999 that involved fungal screening in vitro, chemical controls. Each fruit was immersed in the treatments (suspension of spores) and then inoculated by spraying the pathogen. The incidence of the disease in the wounds and around them was then assessed. Several antagonists were efficient in vitro using cellophane membrane tests: isolates of Trichothecium spp. (F1, F2 and F4), Trichoderma spp. (F8 and F12), and also with the method of paring culture: isolates of Trichoderma spp. (F7, F8 and F12) and Penicillium sp (F9). In post-harvest the biological control (isolates F1 and F2) showed very good results (above 80% of control) with no statistical differences between them and the best fungicides tested (iminoctadine and azoxystrobin). The phosphite of K showed good results, above 85% of control of latent infections in both experiments.

Caracterização morfológica de isolados de Cryptosporiopsis perennans em diferentes meios de cultura

The mycelial growth and conidial production of nine isolates of Cryptosporiopsis perennans were evaluated on the culture media of potato-dextrose-agar acidified (PDA-acid), malt extract agar (MEA) and V8-agar (V8) under 12 hours of photoperiod at 21°C. Five mm-diameter disks taken from colonies grown for 14 days on PDA medium under 12 hours of photoperiod at 21°C were transferred to Petri dishes with 20 mL of each medium. Colonial morphology, mycelial growth, sporulation and spore dimension were evaluated after 13 days of incubation. The effect of the culture media varied according to isolates. Mycelial growth and conidial production were observed in all tested media. The culture medium V8 was the best medium tested for mycelial growth and conidial production, followed by MEA for all C. perennans isolates. In all culture media the isolates presented a fusiform conidial shape.

Deposição de agrotóxicos pulverizados na cultura da maçã

The objective of this work was to evaluate the distribution of pesticide deposition on two apple varieties (Malus domestica Borkh). Liquid spray with Rhodamine as tracer was sprayed by trailed aircarrier equipment, with two types of calibrations. In one of them itxa0was used the JA-1, JA-2 and JA-3 cone nozzles, and in the other, AVIxa0110 ISO-04 fan nozzles and JA-1 cone nozzles. There were no differences among the calibrations, but the deposition on the plants decreased from the apical to the basal region. On all tested calibrations, 25% of the applied tracer was wasted on the soil.

Etiologia da podridão do coleto de Brachiaria brizantha em pastagens da amazônia

Amazonian pastures formed with Brachiaria brizantha Marandu cultivar (also known as Braquiarao) have been devastated by a new disease since 1995, whose typical symptoms are diseased plants dispersed in pastures. Four Pythium and one Rhizoctonia isolates were recovered from plants in the early stages of infection and infected seeds,. The results of the pathogenic tests showed P. periilum as the main pathogen. Inoculations of healthy plants with the pathogen alone or in mixture resulted in a high rate of disease (p<0.01) when P. periilum and R. solani were present in Braquiarao plant tissues, showing that both pathogens are associated. This is the first report of P. periilum as the primary agent of collar rot on B. brizantha.

Resgate de macieiras antigas no Rio Grande do Sul: uma opção para a manutenção da diversidade genética

Nesse cenario, os programas de melhoramento conduzidos no Brasil e a introducao de novas cvs. sempre mantinham como meta final a obtencao de materiais geneticos semelhantes as caracteristicas da cv. Gala e/ou Fuji, procuravam materiais com maturacao no periodo entre as duas cvs. principais e tinham como alvo a resistencia a sarna da macieira (Venturia inaequalis) utilizando fontes de resistencia semelhantes aos utilizados em outros programas deste tipo no exterior. Nesta situacao, a preocupacao inicial estava centrada no impacto que teria a introducao de uma doenca quarentenaria, numa populacao geneticamente homogenea de macieiras, principalmente porque, nessa epoca, havia importacao macica de porta-enxertos e de plantas enxertadas de diversos paises. Felizmente isto nao ocorreu. Todavia, o surgimento da epidemia da mancha foliar da Gala (Colletotrichum gloeosporioides), iniciada a partir de 1990, e que causou perdas elevadas em toda a regiao produtora de macas no Pais, somada a constatacao da quebra de resistencia a sarna da macieira das cvs. que utilizavam o gene Vf na Europa, deu um alerta aos pesquisadores da Embrapa Uva e Vinho quanto a necessidade de buscar estrategias alternativas que garantissem maior variabilidade para a cultura. Contribuiram para reforcar este tipo de preocupacao a analise e o acompanhamento do sistema produtivo da maca, iniciado a partir de 1997 por uma equipe multidisciplinar que veio discutir e pesquisar os sistemas de Producao Integrada de Macas (PIM) e, posteriormente, a producao orgânica de macas. Nessa epoca, esta discussao ja ocorria nos eventos de Producao Integrada de Frutas na Europa e relatavam-se os primeiros resultados dos esforcos feitos para resgatar as fontes de variabilidade abandonadas ou perdidas durante o processo de melhoramento. Citavase, tambem, a organizacao de uma rede de pesquisa formada por diversos paises europeus a qual tinha a funcao de avaliar macieiras antigas das suas regioes que tivessem potencial para serem utilizadas como cvs. regionais e/ou como fontes de germoplasma para os programas de melhoramento e para estudos de resistencia duravel para as duas doencas mais importantes na Europa: a sarna e o oidio da macieira. As primeiras acoes destinadas ao resgate das cvs. antigas disponiveis no Sul do Brasil foram feitas pela Embrapa Uva e Vinho em 2002, percorrendo-se propriedades rurais e pomares caseiros nas cidades do norte e nordeste do Rio Grande do Sul. Esses locais foram identificados com auxilio das informacoes de produtores e de agentes da Extensao Rural (Emater/RS) e neles verificava-se a sobrevivencia de plantas de idade superior a 60 anos que ainda produziam mesmo sem

Metodologia para observação da camada de cera em maçãs, utilizando microscopia eletrônica de varredura

The fruit epidermis is covered by a thin layer of wax which gives protection to the fruit, mainly against water loss and pathogenic organisms. Several studies using scanning electron microscope have been developed to study that wax. The wax layer visualization through the scanning microscope is difficult due to some problems of sample preparation. The usual procedures cause serious damages to the wax layer or even eliminate it because of its solubilization by some of the reagents. Several researchers have kept the samples at very low temperature (-90oC) during the preparation. Wax observations in Brazil by using electronic scanning microscope have been performed, however in some of them results were not consistent. A relatively simple procedure at the Laboratory of Electron Microscopy at Embrapa Temperate Climate has been tried to overcome such difficulties. Such procedure consists of collecting a small piece of the fruit epidermis (1cm2) taken from the equatorial part of the apples. After sampling it the piece of epidermis is placed on a glass slide hold by the extremes with a sticky tape. The sample on glass slide is kept for 72 hours into a dessicator containing drierite for the sample dehydration. Then, small pieces of the sample (2 mm2) were taken and hold on stubs followed by metalization in gold. Following that, the sample is observed using a Zeiss (DSM - 940A) electronic microscope at a working distance of 15 mm and acceleration voltage of 10 KV. The obtained images made possible to evaluate the action of some experimental treatments which have been used on apples during cold storage.

Evidência molecular da ocorrência de um fitoplasma associado ao lenho mole da macieira

ABSTRACT Apple rubbery wood is an important disease occurring worldwide. Typicalsymptoms have been observed since 80’ decade in orchards located inthe South part of Brazil. In previous studies, grafting has evidenciatedthat the disease had infeccious etiology and visualization of filamentousbodies inside phloem had indicated that a phytoplasma could be associatedwith the disease. In the present study, plants with symptoms of rubberywood were sampled in a commercial orchard in order to demonstrate thepresence of phytoplasma in infected tissue and to identify molecularlythat the organism. Using nested PCR with universal primers pairs R16mF2/ Ribeiro, L.F.C.; Bedendo, I.P.; Sanhueza, R.M.V. Molecular evidence for an association of a phytoplasma with apple rubbery wood. SummaPhytopathologica , v.33, n.1, p.30-33, 2007.Additional keywords: Mollicutes, phytophathogenic prokaryontes, phytoplasmal diseases. R1 and R16F2n/R2, phytoplasma was consistently detected insymptomatic plants. Identification conducted with specific primer pairR16(III)F2/R1 in nested PCR demonstrated that the phytoplasma was amember of group 16SrIII. RFLP analyses with endonucleases

Imersão em água quente no controle pós-colheita da podridão branca em maçãs cv. Fuji

Post harvest control of white rot on cv. Fuji apples by hot water heat treatments The objective of the present study was to evaluate the efficacy of heat treatments on the control of white rot caused by Botryosphaeria dothidea on ‘Fuji’ apples (Malus domestica). Apples were immersed for either 1, 2 or 3 min in hot water at 47, 49 or 52 °C. Before the heat treatments, the apples were inoculated with the fungus B. dothidea . After the treatments, apples were stored at 0-1 °C in controlled atmosphere (CA) with 1.2 - 1.6 kPa O 2 and 0.2 - 0.4 kPa CO 2 or in refrigerated air storage for one, three or five months. After each storage period, samples were transferred to room temperature for seven days and evaluated for lesion diameter and quality parameters. Hot water heat treatment at 47 °C for 3 min reduced lesion diameter of Fuji apples under CA storage. The CA storage resulted in better quality apples.