Adalberto Corrêa Café Filho

Sistemas de cultivo, sucessões de culturas, densidade do solo e sobrevivência de patógenos de solo

The objective of this work was to evaluate the effect of cropping systems and crops cultivated previously to common beans (Phaseolus vulgaris L.) on soil density and soil populations of Rhizoctonia spp. and Fusarium spp. Previous crops included the following legumes: Cajanus cajan,Stylosanthes guianensis cv. Mineirao and Crotalaria spectabilis; and the following grasses: Pennisetum glaucum (cv. BN-2, millet), Sorghum bicolor (cv. BR 304), Panicum maximum cv. Mombaca, Brachiaria brizantha cv. Marandu and a consortium of corn (Zea mays) and B. brizantha. Previous crops were planted in Brazil summer seasons (wet) of 2002, 2003 e 2004, and bean crop (cv. BRS Valente) was planted in the correspondent subsequent winters (dry) of 2003, 2004 and 2005, irrigated by central pivot. Crop residues were incorporated to the soil, in conventional tillage, and kept on the surface, in no tillage management. In general, soil populations of Fusarium spp. and Rhizoctonia spp. were higher in no tillage cropping system. Higher populations of Rhizoctonia spp. were found in heavier soils. Legume crop residue increased soil populations of Rhizoctonia spp. and Fusarium spp. and, therefore, Leguminosae should be avoided as previous crops to common beans, in both cultivation systems. Generally, Gramineae previous crops are supressive to soil populations of Rhizoctonia spp. and Fusarium spp.The objective of this work was to evaluate the effect of cropping systems and crops cultivated previously to common beans (Phaseolus vulgaris L.) on soil density and soil populations of Rhizoctonia spp. and Fusarium spp. Previous crops included the following legumes: Cajanus cajan, Stylosanthes guianensis cv. Mineirao and Crotalaria spectabilis; and the following grasses: Pennisetum glaucum (cv. BN-2, millet), Sorghum bicolor (cv. BR 304), Panicum maximum cv. Mombaca, Brachiaria brizantha cv. Marandu and a consortium of corn (Zea mays) and B. brizantha. Previous crops were planted in Brazil summer seasons (wet) of 2002, 2003 e 2004, and bean crop (cv. BRS Valente) was planted in the correspondent subsequent winters (dry) of 2003, 2004 and 2005, irrigated by central pivot. Crop residues were incorporated to the soil, in conventional tillage, and kept on the surface, in no tillage management. In general, soil populations of Fusarium spp. and Rhizoctonia spp. were higher in no tillage cropping system. Higher populations of Rhizoctonia spp. were found in heavier soils. Legume crop residue increased soil populations of Rhizoctonia spp. and Fusarium spp. and, therefore, Leguminosae should be avoided as previous crops to common beans, in both cultivation systems. Generally, Gramineae previous crops are supressive to soil populations of Rhizoctonia spp. and Fusarium spp.

Neon-S, novo meio para detecção de Sclerotinia sclerotiorum em sementes

Neon medium, originally proposed to verify the viability of sclerotia of Sclerotinia sclerotiorum, suffered modification aiming to detect the pathogen on seeds. A wide-ranged antibiotic and a form of 2,4-D acid that could withstand sterilization were incorporated in the new medium. The ideal concentration of blue bromophenol and the best light and temperature conditions for incubation of seeds on this medium were verified. All ingredients of the new medium were added before sterilization and pH adjustment was unnecessary. This medium, named Neon-S, was compared to the methods recommended for the detection pathogens on seeds by the Brazilian Ministry of Agriculture. Compared to the filter paper test and the germination paper test, the method was faster and more efficient, by reducing the detection time of the pathogen from 37 days to 12 days.

Intensidade do mofo-branco do feijoeiro em plantio convencional e direto sob diferentes lâminas d'água

A gradient of water depths, obtained with the line source irrigation system, and two bean (Phaseolus vulgaris) cultivars, under the conventional and the no-tillage cropping systems, demonstrated increases in white mold intensity caused by Sclerotinia sclerotiorum and sclerotium production with larger water depths. With an initial inoculum concentration of 0.2 sclerotia/kg of soil, the percentage of infected plants varied from 0 to 100% (1998) and from 0 to 12% (1999). A higher and more severe incidence of white mold was verified in plots planted with the cultivar of more prostrate habit, in the conventional cropping system. In both years, disease intensity, production of sclerotia and development of apothecia were lower in the no-tillage cropping system. Finally, in both experiments, about four times more sclerotia was present in the residue of grain collected from conventional tillage plots, than in the no-tillage plots, showing that the production of inoculum for the next crop is much larger in the former than in the latter. This is especially relevant, considering the importance of initial inoculum for monocyclic diseases, such as in the case of white mold, with direct implications for the sustainability of winter bean production in the dry season in Brazil.

Cultural practices and genetic resistance as factors affecting soybean stem canker and plant yield in the Cerrado

Field experiments were conducted in the 1995-96 soybean (Glycine max) growing season to evaluate the effects of cultural practices and host genetic resistance on the intensity of soybean stem canker, caused by Diaporthe phaseolorum f.sp. meridionalis (Dpm). Experiments were conducted in a commercial field severely infected in the previous (1994-95) season. In one study, minimum tillage (MT) and no-tillage (NT) cropping systems were investigated for their effects on disease development and on plant yields in cvs. FT-Cristalina (susceptible) and FT-Seriema (moderately resistant). Another study evaluated the effects of plant densities (8, 15, 21 and 36 plants/m) on disease development in cvs. FT-Cristalina, FT-101 (moderately resistant) and FT-104 (resistant). Disease incidence and severity were consistently lower in NT than in MT, and plant yields were increased by 23% and 14% in the NT system for the susceptible and moderately resistant cultivars, respectively, compared to the yields in the MT system. The Gompertz and Logistic models described well the disease progress curves in all situations. For both susceptible and moderately resistant cultivars, disease severity increased proportionately to the increase in plant densities. At the end of the season, 100% of the plants of cv. FT-Cristalina were infected by Dpm, at all plant densities. Disease levels on cv. FT-101 were intermediate while only very low disease levels were recorded on cv. FT-104. There was a consistent negative correlation between stem canker severity and yield. Some practices demonstrated potential for direct application in disease control, and could be combined considering their additive effects.

Reação de genótipos de melancia ao crestamento gomoso do caule

ABSTRACT Response of watermelon cultivars to gummy stem blightGummy stem blight, caused by Didymella bryoniae, is one ofthe most important watermelon diseases. Nevertheless, there arerelatively few published studies on the response of watermelongenotypes to the disease. This paper reports results of studies on theresponse of commercially available watermelon cultivars to gummystem blight. Leaf infection was studied in a randomized completeblock field experiment with nine watermelon genotypes and fourreplicates. Two plants per experimental plot were inoculated 43 daysafter planting. Cultivars Crimson Sweet, Onix, Rubi, Safira, Eureka,Georgia, Sheila, Savana and Riviera were evaluated. Stem infectionwas studied in the greenhouse, in a completely randomized design,with three replicates, in a 9 X 3 factorial, where plant cultivarscorresponded to factor “a” and pathogen isolates corresponded tofactor “b”. The same nine cultivars were examined following artificialinoculation with mycelial disks inserted into stems, 15 days afterplanting date, when plants were at the first adult leaf stage. The D.bryoniae isolates were UnB 76 (Melon-DF), UnB 75 (Watermelon-PE) and UnB 81 (Pumpkin-DF). In the field experiment, Rivierawas the most resistant genotype, with significantly (P<0.05) lowervalues of leaf infection at 74 and 79 DAP and the smallest area underdisease progress curve (AUDPC). Crimson Sweet, Rubi, Onix andSafira were the most susceptible genotypes based on foliar diseaselevels 74 days after planting and also based on the AUDPCs. In thegreenhouse, Riviera also presented the smallest (P<0.05) AUDPCin stems. A significant correlation (r=0.77) was detected betweendisease measurements in the greenhouse (stem response) and in thefield (foliar response).Keywords: Citrullus lanatus, Didymella bryoniae.

Efeito de fungicidas em Colletotrichum acutatum e controle da antracnose do morangueiro

Eleven fungicides were tested in the field, and their effects on Colletotrichum acutatum, the agent of strawberry (Fragaria X ananassa) flower blight,, were examined in vitro. Treatments and doses tested in the field per 100 l of water were iprodione (75 ml), benomyl (100 g), tebuconazole (50 ml), methyl thiofanate (70g), prochloraz (100 ml), propiconazole (50 ml), mancozeb (200 g), folpet (270 g), copper sulfate (200 g) and chlorothalonil (200 g), sprayed weekly (protectants) or bi-weekly (systemic). Fruit yield and number of blighted flowers were computed. For the in vitro fungitoxicity tests, the rate of mycelial growth rate of conidial germination and appressorium formation were studied in fungicide dilutions. In vitro tests were conducted with 1 and 10 ppm, and subsequently at 0.01, 0.1 and 1 ppm for the most efficient products and at 10, 50 and 100 ppm, for the least efficient a.i. The fungicides that resulted in least mycelial growth at the lowest concentrations were prochloraz and tebuconazole, and the ones that least inhibited mycelial growth the was copper sulfate, chlorothalonil and folpet. Most efficient products for inhibition of conidial germination were chlorothalonil, tebuconazole, prochloraz and benomyl. Most efficient products for inhibition of appressorium formation were chlorothalonil and benomyl. Field results were partially different from in vitro results: prochloraz and copper sulfate had the lowest percentages of blighted flowers (53-55%), whereas benomyl had 100% blighted flowers. Although prochloraz, followed by iprodione, folpet and mancozeb resulted in larger fruit yields, no product alone provided sufficient control of strawberry flower blight.

Occurrence of gummy stem blight in watermelon in the state of Tocantins caused by Didymella bryoniae

Occurrence of gummy stem blight in watermelon in the state of Tocantins, caused by Didymella bryoniae Canker symptoms at the base of stems and brown exudates were observed in watermelon (Citrullus lanatus) plants collected in Formoso Project, Tocantins State. The teleomorphic and anamorphic stages (Didymella bryoniae and Ascochyta cucumis, repectively) were observed. Detailed descriptions, morphometrics and optical and electronic illustrations of both stages are done here for the first time in Brazil. The pathogenicity of several Tocantins isolates was confirmed by artificial

Efeito do espaçamento e da cultivar de feijoeiro sobre a intensidade do mofo-branco e a sanidade de sementes

The effect of spacing among rows and among bean plants, as well as two plant growth habits were evaluated on the intensity of white mold and seed health in two field trials in Brasilia, DF, Brazil. In the first trial, the same population of 27 plants/m 2 was maintained in rows of 30, 45 and 60 cm apart. In the second trial, the spacing among rows was maintained, which resulted in different plant populations of 40, 27 and 20 plants/m 2 , respectively. Disease incidence and severity did not differ

Estabilidade da resistência de Capsicum spp. ao oídio em telado e casa de vegetação

This work reports the resistance of Capsicum spp. genotypes to Oidiopsis taurica. Experiments were first conducted with artificial inoculation in pots in a screenhouse, with a set of 104 genotypes. A similar test was carried out with transplants in soil beds in a greenhouse, with 93 genotypes, selected from those previously tested in the screenhouse. In the screenhouse, plants were spray-inoculated with a conidial suspension of 104 conidia/ml. The source of inoculum in the greenhouse consisted of previously-infected sweet-pepper (Capsicum annuum) plants. Genotypes were separated into five resistance groups, following measurements of four disease variables: disease incidence, sporulation index, leaf severity index, and total disease intensity. In addition, the areas under disease progress curves were determined for each variable. About 77% of the genotypes tested in the screenhouse were highly (HS) or moderately susceptible (MS); 8% moderately resistant (MR); 11% resistant (R); and 4% were highly resistant (HR). About 72% of the genotypes tested in the greenhouse were HS or MS; 11% MR; 9% R and 8% HR. Capsicum annuum was the most susceptible species to O. taurica. Classification of most genotypes according to their resistance remained the same in the two experiments. Capsicum baccatum, C. frutescens and C. chinense had higher frequencies of resistant genotypes, and therefore, are considered to be good sources of resistance to the disease. The best sources of resistance (HR genotypes) were CNPH 39, 161, 363 and 601 (C. baccatum); CNPH 579, 596 and 597 (C. frutescens); CNPH 55 (C. annuum); CNPH 280, 289, 434, 570 and 600 (C. chinense) and CNPH 1424 (C. annuum).

Efeito da freqüência de rega e da umidade do solo sobre a germinação carpogênica de sclerotinia sclerotiorum

The effects of watering frequency and soil moisture status on the carpogenic germination of Sclerotinia sclerotiorum were studied under controlled environmental conditions. Soil and sclerotia were placed in gerbox and periodically watered up to 75 and 100% of saturation, one, two, three and five times a week. There was no sclerotium germination when the soil was watered up to 75% of saturation once a week. On the other hand, soils saturated frequently allowed higher percentage of sclerotia germination, until 70%, as well as higher numbers of apothecia. Independently of the soil water content, germination of sclerotia and production of apothecia increased with watering frequency. Important factors on the carpogenic germination of S. sclerotiorum were the soil moisture and the watering frequency. Frequent watering, even with low water volumes applied, also increased the carpogenic germination.