Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Biological control of eucalyptus bacterial wilt with rhizobacteria(Biological Control, 2015-01) Santiago, Thais R.; Rossato, Mauricio; Romeiro, Reginaldo S.; Mizubuti, Eduardo S. G.; Grabowski, CristhianThe antagonistic potential of 298 rhizobacteria obtained from the rhizosphere and rhizoplane of tomato and eucalyptus plants was assessed for the control of bacterial wilt of eucalyptus caused by Ralstonia solanacearum. Several tests were performed using tomato plants as a screening system to select efficient rhizobacteria. Different methods for antagonist delivery and pathogen inoculation were evaluated: (1) seeds were microbiolized (soaked for 12 h in a suspension of the antagonist propagules) and germinated seedlings had their roots immersed in the pathogen inoculum suspension; (2) seedlings originated from microbiolized seeds were transplanted to soil infested with R. solanacearum and (3) roots of seedlings were immersed in a suspension of propagules of the antagonist and subsequently in a suspension of R. solanacearum. Nine isolates (UFV-11, 32, 40, 56, 62, 101, 170, 229, and 270) were selected as potential antagonists to R. solanacearum as they suppressed bacterial wilt in at least one of the methods assessed. The selected antagonists were evaluated against two isolates of R. solanacearum using in vitro and in vivo (inoculated eucalyptus) tests. Isolates UFV-56 (Bacillus thuringiensis), UFV-62 (Bacillus cereus) and a commercial formulation of several rhizobacteria (Rizolyptus®) suppressed bacterial wilt in eucalyptus protecting the plants during the early stages of development.Item Biological control of coffee rust by antagonistic bacteria under field conditions in Brazil(Biological Control, 2009-02-13) Haddad, Fernando; Maffia, Luiz A.; Mizubuti, Eduardo S. G.; Teixeira, HudsonRust (Hemileia vastatrix) is the most important coffee disease in Brazil. Organic coffee production has increased in the country and a research program aimed to develop alternatives to chemicals for disease control was required. Seven bacterial isolates, isolated from organic coffee plantings and selected in greenhouse tests, were evaluated under commercial organic crop conditions in 2005 (Experiment 1) and 2005/2006 (Experiment 2), in Machado, MG, Brazil. Ten treatments consisting of the seven bacterial isolates, copper hydroxide, calcium silicate and water were applied as three or four monthly sprays in Experiment 1 or 2, respectively. Rust severity and incidence were evaluated monthly. In Experiment 1, the sprays started in January when rust incidence was 23.8%, and none of the treatments reduced rust progress significantly. In Experiment 2, the sprays began in November 2005, when rust incidence was approximately 7.5%. There were significant differences (P < 0.0001) between treatments regarding maximum incidence and severity (as assessed in June, 2006), the rate of increase of the incidence between November 2005 and June 2006 and for the areas under disease progress curves for both rust incidence and severity. Lower values for these treatments were obtained in the plots treated with copper hydroxide or Bacillus sp. isolate B157, and intermediate values with the Pseudomonas sp. isolate P286. In a third experiment conducted in 2007 in Ervália, MG, isolates B157 and P286 were also evaluated; isolate B157 reduced rust intensity as effectively as copper hydroxide. Isolate B157 is considered a potential biocontrol agent for coffee rust for organic crop systems in Brazil.Item Biological control of strawberry gray mold by Clonostachys rosea under field conditions(Biological Control, 2008-05-03) Cota, Luciano V.; Maffia, Luiz A.; Mizubuti, Eduardo S. G.; Macedo, Paulo E. F.; Antunes, Ricardo F.Gray mold, caused by Botrytis cinerea, is an important strawberry disease in Brazil. As a component of a disease management program, we have been evaluating pathogen biological control with Clonostachys rosea, and selected four isolates as potential antagonists to B. cinerea. In 2006 and 2007, under field conditions, we compared the efficiency of the four C. rosea isolates (applied once or twice a week) with a weekly spray of procymidone alternated with captan in controlling gray mold. Following the applications and up to harvest, we evaluated weekly: leaf area colonization by C. rosea (LAC), average number of B. cinerea conidiophores on leaves (ANC), incidence of gray mold on both flowers (Iflower) and fruits (Ifruit), incidence of latent infections on fruits (Ilat), and yield. The applications of C. rosea twice a week provided higher LAC (16.97%), smaller ANC (10.28; 78.22 in the check treatment, sprayed with water), smaller IFlower (10.02%; 50.55% in the check treatment), and smaller IFruit (5.95%; 25.10% in the check treatment). Yield ranged between 3490 and 3750 g plot^−1 with applications of C. rosea twice a week and between 1740 and 1910 g plot^−1 in the check treatment. Ilat was 20% in the check treatment and less than 10% in the other treatments. Based on this 2-year study, at least two weekly applications of C. rosea are required for a successful gray mold management program.