9 research outputs found
Influence of potassium and calcium on the soybean cyst nematode reproduction
No full textThe objective of this work was to evaluate the reproduction of the soybean cyst nematode (SCN) in soybean plants in substract with different potassium (K) and calcium (Ca) doses. The experiment was conducted in a completely randomized block design, with 25 treatments and six replicates. A factorial scheme (5 x 5) was used with five K doses (0; 150; 300; 450; and 600 mg / dm3 ) and five Ca doses (0; 75; 150; 225; and 300 mg / dm3 ). Eighteen days after sowing, plants were inoculated with 4,000 H. glycines race 3 eggs. Thirty days after inoculation a total of three weekly evaluations were performed measuring plant height and stem diameter. Seventy days after inoculation, the following variables were analyzed: measurement of leaf blade, numbers of eggs / pot, cysts / pot, eggs / cyst, females and cysts / root system, eggs / female and the reproduction factor of H. glycines. Root and shoot dry matter were weighed. Then, K and Ca shoot contents of each sample was obtained. There was a significant interaction between K and Ca doses only for number of eggs / female. The K doses significatively influenced the numbers of cysts / pot, eggs / cyst, eggs / pot, females and cysts / root system and reproduction factor. The Ca doses did not influence significatively the nematologic variables analyzed. The K-Ca interaction affected all crop-related variables analyzed. A significative K-Ca interaction was observed for Ca contents in shoot dry matter. The K contents were only influenced by potassium doses amended to the soil.O objetivo deste trabalho foi avaliar, em casa de vegetação, a reprodução do nematoide do cisto (Heterodera
glycines) em plantas de soja, cultivadas em substrato contendo diferentes doses de potássio (K) e cálcio (Ca). O
delineamento experimental utilizado foi o de blocos casualizados, com 25 tratamentos e seis repetições. Foi
utilizado esquema fatorial 5 x 5, com cinco níveis de K (0, 150, 300, 450 e 600 mg / dm3
) e cinco níveis de Ca
(0, 75, 150, 225 e 300 mg / dm3
). Dezoito dias após a semeadura, as plantas foram inoculadas com 4.000 ovos
de H. glycines, raça 3. A partir dos 30 dias após a inoculação, foram realizadas semanalmente, avaliações da
altura e de diâmetro do caule das plantas, totalizando-se três avaliações. Setenta dias após a inoculação, as
seguintes variáveis foram analisadas: área foliar, números de ovos / vaso, cistos / vaso, ovos / cisto, fêmeas e
cistos / sistema radicular, ovos / fêmea e o fator de reprodução do nematoide. Também foram determinadas
as massas da matéria seca da parte aérea (caule + folhas) e das raízes. Os teores de K e Ca na matéria seca da
parte aérea também foram analisados. Houve interação significativa somente entre as doses de K e Ca para
número de ovos por fêmea. As doses de K influenciaram, significativamente, os números de cistos / vaso,
ovos / cisto, ovos / vaso, fêmeas e cistos / sistema radicular e o fator de reprodução. As doses isoladas de Ca
não influenciaram significativamente nenhuma variável nematológica analisada. A interação K-Ca afetou todas
as variáveis agronômicas analisadas. Observou-se interação K-Ca significativa para os teores de Ca na matéria
seca da parte aérea. Os teores de K foram influenciados somente pelas doses de K adicionadas ao solo
Nutrition in bean plants and anthracnose intensity in function of silicon and copper application.
No full textNutrition in bean plants and anthracnose intensity in function of silicon and copper application. The objective of this work was to evaluate the effect of calcium silicate and copper sulfate on anthracnose intensity and nutrition of bean plants. The experiment was conducted using an experimental design in randomized blocks following a 4 x 4 factorial arrangement , (four levels of calcium silicate and four levels of copper sulfate) and two additional treatments (plants without inoculation and plants sprinkled with Benomyl). Four evaluations of the incidence and severity of anthracnose were done, in addition to measuring, total leaf area. At the end of the evaluations, incidence: and data were integrated over time, obtaining the area under disease progress curve (AUDPC). Contents of N, P, K, Ca, Mg, B, Cu, Fe, Mn, Zn, Si and lignin were determined in the aerial Part. A linear decrease of the intensity AUDPC was observed with the increase of the doses of calcium silicate. The severity AUDPC was influenced by the doses of copper, obtaining a reduction of 35% on the higher dosage. The supply of silicon and copper altered the content of the K, mg, S, Zn, Ca and Si in the aerial part of the bean plants
Efeito de fungicidas recomendados para o controle de ferrugem do cafeeiro sobre Colletotrichum spp.
No full textOs fungicidas triadimenol e oxicloreto de cobre são recomendados para o controle da ferrugem
do cafeeiro. Neste trabalho foi estudado o efeito destes fungicidas contra Colletotrichum sp., agente causador da
antracnose em frutos maduros de café, nas doses recomendada para o controle da ferrugem. O experimento foi
conduzido no ano agrícola 2001/2002, em um cafezal de oito anos da cultivar Catuaí 99, no município de Lavras,
MG. O delineamento experimental utilizado foi em blocos ao acaso em esquema fatorial com dois fungicidas e três
doses, mais uma testemunha adicional, com 3 repetições. Os fungicidas triadimenol e o oxicloreto de cobre foram
utilizados nas dosagens de 100%, 75% e 50% da dose comercial recomendada. Em cada parcela experimental foram
colhidos, ao acaso, 400 frutos de café. Desses retiraram-se 100 ao acaso e quantificou-se a incidência de antracnose
pela observação visual dos sintomas em microscópio estereoscópio. Os fragmentos dos tecidos de frutos, sadios e
com sintomas, foram inicialmente tratados em solução de hipoclorito de sódio a 2% por 5 minutos, secados, colocados
em meio BDA e incubados a 20ºC, com regime de 12 horas de luz durante sete dias. Houve diferença significativa
entre os tratamentos com fungicidas e a testemunha, com redução da antracnose em frutos de 45% e 34% pelo
oxicloreto de cobre e triadimenol, respectivamente, quando comparados à testemunha
Efeito de fungicidas recomendados para o controle de ferrugem do cafeeiro sobre Colletotrichum spp.
No full textOs fungicidas triadimenol e oxicloreto de cobre são recomendados para o controle da ferrugem
do cafeeiro. Neste trabalho foi estudado o efeito destes fungicidas contra Colletotrichum sp., agente causador da
antracnose em frutos maduros de café, nas doses recomendada para o controle da ferrugem. O experimento foi
conduzido no ano agrícola 2001/2002, em um cafezal de oito anos da cultivar Catuaí 99, no município de Lavras,
MG. O delineamento experimental utilizado foi em blocos ao acaso em esquema fatorial com dois fungicidas e três
doses, mais uma testemunha adicional, com 3 repetições. Os fungicidas triadimenol e o oxicloreto de cobre foram
utilizados nas dosagens de 100%, 75% e 50% da dose comercial recomendada. Em cada parcela experimental foram
colhidos, ao acaso, 400 frutos de café. Desses retiraram-se 100 ao acaso e quantificou-se a incidência de antracnose
pela observação visual dos sintomas em microscópio estereoscópio. Os fragmentos dos tecidos de frutos, sadios e
com sintomas, foram inicialmente tratados em solução de hipoclorito de sódio a 2% por 5 minutos, secados, colocados
em meio BDA e incubados a 20ºC, com regime de 12 horas de luz durante sete dias. Houve diferença significativa
entre os tratamentos com fungicidas e a testemunha, com redução da antracnose em frutos de 45% e 34% pelo
oxicloreto de cobre e triadimenol, respectivamente, quando comparados à testemunha
Manganese and fluorine suppress bacterial blight on coffee seedlings grown in a nutrient solution
No full textThe use of manganese (Mn) and fluorine (F) in the management of bacterial blight were evaluated in coffee seedlings grown in a nutrient solution. The experiment was carried out with the cultivar Catuaí Vermelho IAC 99. The treatments consisted of the combination of five doses of Mn with five of F, applied via leaf, using Mn sulfate and sodium fluoride, in a 5x5 factorial scheme. The plants were inoculated with bacterial suspension seven days after foliar application of F and Mn doses. The incidence and severity assessments were performed at an interval of 24 hours for 10 days. Photosynthetic activity was assessed using the infrared gas analyzer. Stomatal conductance, photosynthesis, transpiration, PAR radiation and internal CO2 were analyzed. The chlorophyll content was calculated indirectly. The leaf analysis was performed by digestion in HNO3 to determine the levels of Mn. Variablessuch as Area Under Incidence Disease Progress (AUIDP), Area Under Severity Disease Progress (AUSDP), chlorophyll a, b, and total concentrations and photosynthesis were submitted to the Shapiro-Wilk test. The treatment means were subjected to linear regression analysis. Data were analyzed using software R. There was a significant interaction (P <0.05) between the concentrations of Mn and F for the AUIDP and (AUSDP). Doses between 0.7 and 1.4 g L-1 of Mn combined with doses of 0.10 to 0.12 g L-1 of F were more effective in suppressing the bacterial blight, after analysis for both variables. The increase in Mn concentrations in leaves reduced liquid photosynthesis. The interaction between Mn and F suppressed the bacterial blight intensity of the coffee plants in nutrient solution.
Key words: Coffea arabica L.; Mineral nutrition; Epidemiology; Superphosphate simple; Micronutrients
Detection and factors that induce Stenocarpella spp. survival in maize stubble and soil suppressiveness under tropical conditions.
No full textStenocarpella spp. causes stalk and ear rot in maize and overwinters in stubble during the off-season. Understanding the factors that guide saprophytic colonization is a crucial strategy for management. In this study, we analyzed the abiotic factors and crop management practices in relation to the inoculum of Stenocarpella spp. in stubble by qPCR. Soil samples were used for suppressiveness tests against Fusarium verticillioides, Fusarium graminearum, and Stenocarpella maydis. In the 29 fields, different levels of Stenocarpella spp. were detected. Only three fields were considered suppressive for the three pathogens. Heat maps showed that soil suppressiveness was inversely related to the pathogen concentration, and the suppressiveness of one pathogen was correlated with the suppressiveness of other pathogens. Under no-tillage systems in which rotation with soybeans was adopted, Stenocarpella spp. were detected at lower concentrations than in areas that adopted notillage systems with maize monocultures. While in tillage systems, the maize?maize monocropping increases the inoculum level of Stenocarpella spp. Crop rotation is a factor related to the observed reduction in the pathogen concentration and increases in the broad-spectrum antagonistic microbial communities. These communities guide the suppressiveness of soil-borne diseases in maize fields cultivated under tropical conditions
fungicides
No full textBackground Quinone outside inhibitor (QoI) fungicides have not been effective in controlling the wheat blast disease [Pyricularia oryzae Triticum lineage (PoTl)] in Brazil. The first report of resistance of PoTl to QoIs in this country occurred in 2015. This study aimed to test hypotheses about the changes in fitness parameters and competitive advantage of the QoI-resistant (R) PoTl isolate group compared to the sensitive (S) isolate group. Mycelial growth on PDA medium and in vivo conidial production, incubation period and disease severity were analyzed as fitness parameters. The competitive ability was measured on wheat leaves and heads inoculated with mixtures of R:S isolates at the following proportions: 0S:100R, 20S:80R, 50S:50R, 80S:20R, 100S:0R, and 0S:0R. Results The QoI-R isolate group had significantly higher fitness than the sensitive isolate group, considering both in vitro and in vivo parameters. The highest in vivo conidial production on wheat leaves and the highest leaf and head disease severity were detected when resistant strains were predominant in the isolate's mixtures (20S:80R or 0S:100R proportions), in the absence of fungicide pressure. Conidia harvested from wheat blast lesions on leaves inoculated with 20S:80R and 0S:100R mixtures were resistant to QoIs in vitro assays based on discriminatory doses of the fungicide. Conclusion Therefore, QoI resistance facilitated a higher fitness and a competitive advantage in PoTl, which contrasts with the evolutionary theory that associates a fitness cost to fungicide resistance. We discuss the evolutionary and ecological implications of the higher fitness as found in the fungicide-resistant adapted populations of the wheat blast pathogen. (c) 2022 Society of Chemical Industry.Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)National Council for Scientific and Technological DevelopmentConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ Fed Lavras, Dept Plant Pathol, Lavras, BrazilAgr Engn & Soils Sao Paulo State Univ, Dept Crop Protect, Sao Paulo, BrazilState Univ Tocantina Reg Maranhao, Ctr Agr Sci Campus Imperatriz, Sao Luis, Maranhao, BrazilAgr Engn & Soils Sao Paulo State Univ, Dept Crop Protect, Sao Paulo, BrazilFAPEMIG: CAG-APQ01975-15National Council for Scientific and Technological Development: CNPq 305482/2017-3National Council for Scientific and Technological Development: 432306133/2021-0National Council for Scientific and Technological Development: 313825/2018-1FAPESP: Fapesp2018/21197-0FAPESP: Fapesp 2019/12509-
Phosphites for the management of anthracnose in soybean pods
No full textThe incidence of soybean anthracnose reduces yields and leads to financial losses. Among several management practices to control this disease, use of phosphites (Phi) can act by providing mineral nutrition, inducing resistance in the host and causing direct toxicity to the pathogen. The aim of this study was to investigate the effectiveness of phosphites in the management of anthracnose in soybean pods, in the transmission of the pathogen and the activities of plant defense enzymes. Soybean plants were sprayed with potassium (KPhi), manganese (MnPhi), zinc (ZnPhi), copper (CuPhi) phosphites and fungicide epoxiconazole + piraclostrobin at V4, R1 and R3 stages and inoculated with Colletotrichum truncatum isolate in the R3 stage. The anthracnose severity, the incidence of C. truncatum in soybean seeds, activities of catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) enzymes and contents of soluble lignin and total soluble phenols were evaluated. KPhi, CuPhi and MnPhi reduced the severity of anthracnose, the transmission of the C. truncatum, increased lignin content and SOD, POX and CAT enzymatic activity. Phosphites can be utilized in the management of anthracnose in soybean
