Biocontrol of gray mold in tomato plants by Clonostachys rosea

Greenhouse conditions are favorable to the growth of Botrytis cinerea, and an increase in the occurrence of gray mold caused by this pathogen is therefore expected. Biocontrol using microbial antagonists is one of the approaches to control the pathogen. In previous experiments, Clonostachys rosea isolates suppressed B. cinerea in tomato leaves, but it was not evaluated in wounds caused during pruning, where the pathogen predominantly infects. Here, the efficacy of four C. rosea isolates to control B. cinerea in wounded tomato stems was evaluated. Influence of the following factors on the antagonist’s efficiency were evaluated: i) application time of C. rosea respectively to time for B. cinerea inoculum deposition, ii) conidial concentration of C. rosea, and iii) application of individual isolates versus isolate mixture. Results indicated that the four C. rosea isolates are effective in controlling gray mold, and that they may be applied either individually or as a mixture. The biocontrol efficiency of C. rosea was higher when it was applied 1 day before or simultaneously with the pathogen inoculation at a concentration of 106 conidia/mL- 1, reaching 100 % in stem segments and more than 90 % in whole plants. The antagonist has potential to be used in greenhouse tomato, especially in an integrated management context

Biological control of coffee rust by antagonistic bacteria under field conditions in Brazil

Rust (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

Cultural and Aggressiveness Variability of Cercospora coffeicola

Although brown eye spot of coffee, caused by Cercospora coffeicola, is important for coffee production in Brazil, there is a general lack of knowledge regarding the disease. In this study, we evaluated the variability of both the cultural and aggressiveness traits of 60 isolates from coffee plants grown under conventional and organic systems in three regions of Minas Gerais State, Brazil. Variability among the isolates was detected with regard to all of the traits and was unrelated to an effect of either the region or cropping system. Mycelial growth, cercosporin production and sporulation were assessed in the laboratory. Of the 60 isolates, 27 did not sporulate at 25°C; the mycelial growth of all of the isolates and cercosporin production by 18 of the isolates linearly increased as the temperature rose from 18 to 26°C. We inoculated six selected isolates on plants of two coffee cultivars (ÔCatuaı ́ Vermelho IAC44Õ and ÔCatucaı ́ Vermelho 785-15Õ) and evaluated the incubation period (IP), latent period (LP) and disease severity. All three of these traits were affected by temperature postinoculation and KCl amendment. The significant correlations were as follows: IP and LP in both cultivars; severity and leaf fall in both cultivars; and cercosporin production in vitro and severity values in ÔCatucaı ́ Vermelho 785-15Õ. In conclusion, we found that (i) C. coffeicola is highly variable for both cultural and aggressiveness traits; (ii) laboratory and glasshouse experiments were suitable to assess the pathogen variability; (iii) research protocols should account for the effect of environmental factors, such as temperature and KCl, on the traits evaluated; and (iv) these protocols should include the assessment of the IP instead of the LP, as both are correlated, and the IP is easier to evaluate

Componentes de resistência em cebola a Colletotrichum gloeosporioides

A antracnose foliar causada por Colletotrichum gloeosporioides é importante nas regiões cebolicultoras da América Latina, África e Ásia, mas há poucos estudos relacionados à resistência ao patógeno. Assim, neste trabalho, conduzido em condições de casa de vegetação, avaliaram-se componentes de resistência de oito cultivares e dois acessos de cebola (Allium cepa) a quatro isolados do patógeno, inoculados por atomização de suspensão de inóculo ou deposição de discos de micélio em folhas. Detectaram-se diferenças significativas entre cultivares/acessos, na inoculação por atomização, quanto à freqüência de infecção inicial e à taxa de progresso monocíclico da doença (rg) e, na inoculação com disco de micélio, quanto ao período de incubação e área da lesão. Determinaram-se os coeficientes de correlação (r) dos componentes de resistência estimados na inoculação por atomização. Os valores de r foram 0,98 entre severidade estimada visualmente aos nove dias da inoculação (SEV9) e área abaixo da curva de progresso da doença (AACPD); 0,80 entre SEV9 e severidade estimada por medidor de área foliar (SEV); 0,72 entre SEV9 e rg; 0,64 entre SEV9 e freqüência de infecção aos nove dias da inoculação; 0,81 entre SEV e AACPD e 0,64 entre SEV e rg. Em vista dos valores significativos de r associados a SEV9 e da não necessidade de escala para estimar esse componente, SEV9 é potencialmente útil na avaliação de germoplasma de cebola frente a C. gloeosporioides. Na inoculação por atomização, mais rápida e simples de execução, obtiveram-se maior eficiência de infecção e menor variabilidade de respostas, e deverá ser adotada em estudos futuros.Despite the importance of onion (Allium cepa) leaf anthracnose caused by Colletotrichum gloeosporioides in Latin America, Africa, and Asia, few studies have focused on host resistance to the pathogen. Therefore, in this study, resistance components of two cultivars and eight accessions of onion to four isolates of C. gloeosporioides were evaluated under greenhouse conditions. Inoculations were performed either by spraying inoculum suspension or by placing a mycelial disc on the leaf. The cultivars and accessions differed significantly regarding initial infection frequency and monocyclic progress rate (rg) with the spray-inoculation, and regarding incubation period and lesion area with the mycelial-disc inoculation. Correlation coefficient (r) values were estimated between the components with the mycelial disk inoculations. Values of r were 0.98 between disease severity visually assessed nine days after inoculation (SEV9) and area under the disease progress curve (AUDPC), 0.80 between SEV9 and disease severity assessed with the leaf area meter (SEV), 0.72 between SEV9 and rg, 0.64 between SEV9 and infection frequency nine days after inoculation, 0.81 between SEV and AUDPC, and 0.64 between SEV and rg. Considering both the significant r values associated with SEV9 and that to estimate SEV9 there is no need of rating diagrams, this component is potentially useful to evaluate onion germplasm against C. gloeosporiodes. The spray inoculation procedure was faster, simpler, and provided higher infection efficiency and lower variability than the mycelial disk inoculation technique. Therefore, this should be the preferred inoculation procedure when assessing onion germplasm

Pre-harvest calcium sulfate applications affect vase life and severity of gray mold in cut roses

Gray mold, caused by Botrytis cinerea Pers. Fr., is a major disease in roses. The effect of spraying rose (Cultivar ‘Kiss’) buds with calcium sulfate on the intensity of gray mold was evaluated. Calcium sulfate was sprayed on the buds at different schedules and concentrations before harvest. Thereafter, the buds were harvested and either inoculated or not with B. cinerea. The treatments reduced both the progress and severity of gray mold and increased vase life of the flowers. Good results were achieved with 10 and 20 mM calcium sulfate, applied 24 h before harvest. In the uninoculated assay, the maximum percentages of reduction of the area under the disease progress curve (AUDPC) and of severity were 86% and 86%, respectively, and in the inoculated assay, 68% and 76%, respectively. Vase life of the flowers was increased at least 30% in the assay without inoculation and 20% in the assay with inoculation. Spraying roses with calcium sulfate at 10 mM or 20 mM one day before harvest is recommended to control gray mold after harvest

Etiologia do oídio do eucalipto

Compararam-se isolados de Oidium sp. obtidos de mudas de eucalipto (Eucalyptus spp.) com isolados de Erysiphe cichoracearum, originário de dália, e Sphaerotheca pannosa de roseira (Rosa sp.), por meio de características morfológicas. Com base nas características morfológicas (fase anamórfica) do tubo germinativo, do micélio, do apressório, de conidióforos e conídios e na presença de corpos de fibrosina, concluiu-se que o isolado de Oidium, obtido de eucalipto é similar ao de roseira, descrito como S. pannosa. Inoculações dos isolados do fungo originários de todos os hospedeiros estudados, indicaram que S. pannosa, obtido de roseira, e E. cichoracearum, de dália (Dahlia sp.), foram patogênicos a mudas de Eucalyptus pellita, uma das espécies mais suscetíveis a esta doença, em condições de casa de vegetação.Isolates of Oidium spp. from Eucalyptus pellita were compared to Erysiphe cichoracearum, obtained from Dahlia sp. and Sphaerotheca pannosa, from Rosa sp. Based on the morphological characteristics of the anamorph, it was concluded that the Oidium isolate from eucalypt was similar to the isolate from rose identified as S. pannosa. Inoculations of Oidium isolates from all studied host species showed that S. pannosa obtained from eucalypt and rose, and E. cichoracearum from Dahlia sp. were pathogenic to seedlings of Eucalyptus pellita, one of the most susceptible species to the pathogen, under greenhouse conditions