Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Virulence and impact of brazilian strains of Puccinia psidii on hawaiian ‘Ōhi‘a (Metrosideros polymorpha)(Pacific Science, 2014-01) Silva, André Costa da; Andrade, Pedro Magno Teixeira de; Alfenas, Acelino Couto; Graça, Rodrigo Neves; Cannon, Phil; Hauff, Rob; Ferreira, Diego Cristiano; Mori, SylviaA single strain of Puccinia psidii, the causal agent of rust disease on Myrtaceae, was recently reported on multiple myrtaceous hosts in Hawai‘i, but this strain has caused only mild levels of damage to the state’s predominantn ative forest tree, ‘öhi‘a ( etrosideros polymorpha). Multiple other strains of Puc Mcinia psidii have been identified from Brazil and characterized via extensive sampling and microsatellite analyses. Potential effects of other Brazilian P. psidii strains on Hawai‘i’s ‘öhi‘a were investigated with two inoculation experiments conducted in Brazil. The first, a split-plot experiment, was conducted to deter- mine pathological impact of five Brazilian P. psidii strains on ‘öhi‘a seedlings and to assess variation in susceptibility of seedlings from six different open- ollinatedp ‘öhi‘a parent trees to each P. psidii strain. The second experiment was conducted to determine influence of the rust disease on growth and survival of ‘öhi‘a seedlings. Three of the five P. psidii strains were highly virulent on most of the inoculated ‘öhi‘a seedlings (93% 00% infection rates), and none of the ‘öhi‘a–1 families used in this test showed significant resistance. The other two strains tested were much less virulent. Infection by the highly virulent strains of P. psidii resulted, on average, in a 69% reduction in height growth and 27% increase in mortality of ‘öhi‘a seedlings at 6 months postinfection. These results have immediate implications for designing Hawai‘i’s quarantine barriers.Item Guava fruit loss caused by rust(Summa Phytopathologica, 2014-03-11) Maffia, Luiz Antônio; Silveira, Silvado Felipe da; Martins, Marlon Vagner ValentimThe aim of this paper was to estimate the loss caused by rust (Puccinia psidii) to 'Paluma' guava production in orchards located in Rio de Janeiro State. The disease intensity on the reproductive organs of plants was observed during two chemical control experiments carried out in 2003 and 2004. The loss was estimated based on simple linear regression and the production reduction (fruit number and weight ha-1) on the incidence of diseased buds and fruits. In the first experiment, no relationship was established between incidence of diseased buds and loss since there was a delay in spraying and the incidence of buds showing rust was high (mean of 47%) at the beginning of flowering. In the second experiment (2003-2004), spraying occurred at the beginning of the epidemics and there was a linear relationship between incidence of diseased buds and loss, justifying fungicide intervention at this stage. For the fruiting stage, a significant relationship was found between incidence of diseased fruits and loss in both experiments. In the absence of chemical control, rust reduced fruit production by around 90%.Item Pre-Infection stages of Austropuccinia psidii in the epidermis of Eucalyptus hybrid leaves with different resistance levels(Forests, 2017-10-17) Silva, Renata Ruiz; Silva, André Costa da; Rodella, Roberto Antônio; Serrão, José Eduardo; Zanuncio, José Cola; Furtado, Edson LuizRust is a major Eucalyptus spp. disease, which is especially damaging for early-stage plants. The aim of this study was to verify the pre-infection process of Austropuccinia psidii (A. psidii) in the leaves of three phenological stages of Eucalyptus clones with different resistance levels. Plants from the hybrids of Eucalyptus urophylla × Eucalyptus grandis (E. grandis) with variable levels of resistance to this disease were used. The pathogen was inoculated in vitro on abaxial leaf discs of first, third, and fifth leaf stages and maintained under conditions suitable for disease development. Subsequently, samples from these discs were collected 24 and 120 h after inoculation and processed using scanning electron microscopy analysis. No symptoms were seen in any leaf stage of the resistant clone. Additionally, a low incidence of A. psidii germination (1.3–2%) and appressoria (0–0.5%) in three leaf stages was observed. However, the first leaf stage of the susceptible clone presented germination of large numbers of urediniospores (65%) with appressoria (55%) and degradation of the cuticle and wax. From the third stage, the percentage of germinated urediniospores (<15%) and appressoria (<2%) formation of this clone decreased. Protrusions on the leaf surface, associated with the pathogen, were observed on the first and third leaf stages of the resistant clone and on the fifth stage of the susceptible clone, suggesting a possible defensive plant reaction.Item Eficiência de fungicidas sistêmicos no controle da ferrugem do Eucalyptus(Revista Árvore, 2008-08-22) Zauza, Edival Ângelo Valverde; Couto, Michele Margarido Fonseca; Maffia, Luiz Ântonio; Alfenas, Acelino CoutoAvaliaram-se os efeitos curativo e protetor e o tempo de absorção de fungicidas sistêmicos no controle da ferrugem do eucalipto. Azoxyztrobin, triadimenol, tetraconazole, tebuconazole e epoxiconazole + pyraclostrobin apresentaram 100% de ação curativa quando aplicados até quatro dias após a inoculação. Aplicados após sete dias, apenas azoxystrobin, tebuconazole e epoxiconazole + pyraclostrobin mantiveram o efeito curativo. Aos 10 dias depois da inoculação, os fungicidas reduziram a infecção, mas não controlaram totalmente a doença. Além do efeito curativo, azoxystrobin e triadimenol proporcionaram efeito protetor quando aplicados até 21 dias antes da inoculação de P. psidii. Avaliou-se o tempo mínimo de absorção de azoxystrobin, tebuconazole, triadimenol e trifloxystrobin. Esses quatro fungicidas foram absorvidos pela planta em todos os intervalos testados - 30, 60, 90 e 120 min - e inibiram a infecção de P. psidii em mudas de eucalipto.Item Avaliação de clones de eucalipto para resistência à ferrugem em condições de micropropagação(Revista Árvore, 2012-06-04) Aun, Cristina Pierroti; Mafia, Reginaldo Gonçalves; Marchesi, Helen PachecoA ferrugem, causada pelo fungo Puccinia psidii, é uma das doenças mais frequentes nos plantios de eucalipto no Brasil. Atualmente, o plantio de clones resistentes constitui a principal estratégia para o controle da doença no campo. Para selecionar clones resistentes, é fundamental inocular e avaliar a resposta fenotípica de diferentes materiais genéticos, o que demanda tempo e recursos. Para facilitar e acelerar essa etapa do programa de melhoramento genético, o objetivo deste trabalho foi avaliar a resistência em paralelo à etapa de multiplicação dos clones de eucalipto pela técnica de micropropagação. Para isso, seis clones foram multiplicados em meio MS, modificado nas fases de multiplicação, alongamento e enraizamento. Após 60 dias de incubação, os explantes foram inoculados com suspensão de esporos do patógeno ajustada para 2x10^4 urediniósporos mL^-1. Os explantes foram incubados a 24 ± 2 ºC, fotoperíodo de 14 h de luz com intensidade de 20 ∝mol.s^-1.m^-2. Após 7, 11 e 14 dias da inoculação, avaliou-se a incidência da doença. Observou-se que as reações dos genótipos avaliados em condições de micropropagação foram altamente correlacionadas com os fenótipos determinados pelo procedimento-padrão de inoculação. Assim, o uso desse protocolo permite avaliar grande número de genótipos, com maior rapidez e precisão.Item Development of microsatellite markers for the guava rust fungus, Puccinia psidii(Molecular Ecology Resources, 2008-03) Zhong, Shaobin; Yang, Baojun; Alfenas, Acelino CoutoWe developed and characterized 15 polymorphic microsatellite markers present in the genome of the guava rust fungus, Puccinia psidii. The primers for these microsatellite markers were designed by sequencing clones from a genomic DNA library enriched for a simple sequence repeat (SSR) motif of (AG). All these 15 primer pairs successfully amplified DNA fragments from a sample of 22 P. psidii isolates, revealing a total of 71 alleles. The observed heterozygosity at the 15 loci ranged from 0.05 to 1.00. The SSR markers developed would be useful for population genetics study of the rust fungus.