Different temperatures on mycelial growth of Corynespora cassiicola isolates causal agent of soybean target spot.

Soybean target spot caused by Corynespora cassiicola is a common disease in Brazil. The aim of this study was to evaluate different temperatures on mycelial growth of C. cassiicola isolates obtained from three soybean growing regions in Brazil. Isolates from São Paulo, Paraná and Mato Grosso states were provided by Embrapa Soja. The isolates studied were MT13, PR21, MT29, MT67, SP70, PR27, PR28, PR06, PR02 and MT04. Mycelium plug of 0.5 cm in diameter of each isolated were transferred to PDA media. The plates were incubated in BOD at 10°C, 15°C, 20°C, 23°C, 25°C, 27°C and 30°C temperatures with 12 hours photoperiod. The experimental design was randomized, with 10 isolates, 7 temperatures and 5 replicates. The assessments were made by daily measurements of mycelial growth. Mycelial growth curves were established over time for each temperature using linear regression (Y= A+BX, where Y is the mycelial growth, X is time, A is the intercept and B mycelial growth rate). A mycelial growth curve was set with the ?B? values as a function of temperature for beta generalized equation: Y = B1 ((B2-X)^B4) ((B3-X)^B5, where Y is the mycelial growth rate, X the temperature and the parameters B2 and B3 represent the minimum and maximum temperatures, respectively. The isolates grew at all temperatures studied, except PR21 isolated which did not grow at 10ºC and 30ºC temperature. The increase of temperature caused greater mycelial growth however MT13, PR 27, SP70 and PR02 showed a decrease in mycelial growth at 30ºC temperature. The minimum and maximum temperature estimated by the generalized beta function was between 7,2 ºC and 32,5ºC respectively

Probable consequences of the mitigation of citrus canker eradication methodology in São Paulo state

Recentemente a Secretaria de Agricultura e Abastecimento do estado de São Paulo abrandou os critérios relacionados à erradicação do cancro cítrico. Em abril de 2009 mais de 99,8% dos talhões comerciais de laranjeiras doces estavam livres da doença em São Paulo. Abrandar a metodologia de erradicação significa comprometer esse elevado nível de sanidade dos pomares e a competitividade da citricultura, com reflexos negativos financeiros e ambientais. Diante desses fatos sugere-se: a) que a erradicação da doença volte a ser feita como anteriormente utilizada; ou b) a adoção de uma nova metodologia de erradicação, mais efetiva na supressão da doença, quando em novos levantamentos amostrais de cancro cítrico em São Paulo forem encontradas incidências de talhões comerciais com a doença superiores a 0,36%. Essa incidência foi calculada comparando-se pelo teste de Duncan (P<0,05) os levantamentos amostrais de cancro cítrico realizados de 1999 a 2009. A diferença mínima significativa encontrada foi de 0,28. A menor incidência do cancro cítrico em São Paulo foi de 0,08%, observada em 2001. Dessa forma, como alternativa, propõe-se a adoção de uma metodologia mais drástica de erradicação do cancro cítrico quando em um novo levantamento amostral for detectado mais que 0,36% de talhões comerciais com cancro cítrico.Recently the São Paulo state government mitigated its citrus canker eradication methodology adopted since 1999. In April 2009 at least 99.8% of commercial sweet orange orchards were free of citrus canker in São Paulo state. Consequently the mitigation of the eradication methodology reduced the high level of safety and the competitiveness of the citrus production sector in São Paulo state, Brazil. Therefore we suggest the re-adoption of the same eradication methodology of citrus canker adopted in São Paulo from 1999 to 2009, or the adoption of a new methodology, effective for citrus canker suppression, because in new sample surveys citrus canker was detected in &gt;0.36% of affected orchards. This incidence threshold was calculated by using the Duncan test (P<0.05) to compare the yearly sample surveys conducted in São Paulo state to estimate citrus canker incidence between 1999 and 2009. The calculated minimum significant level was 0.28% among sample surveys and the lowest citrus canker incidence in São Paulo state was 0.08%, occurring in 2001. Thus, as an alternative, we suggest the adoption of a new eradication methodology for citrus canker suppression when a new sample survey detected &gt;0.36% of affected orchards in São Paulo state, Brazil

Influência da temperatura e da luz na esporulação e germinação de basidiosporos de Thanatephorus cucumeris, agente da mancha areolada da seringueira.

Resumo apresentado no XXI Congresso Brasileiro de Fitopatologia, Salvador, 1988. Resumo 051

Piscicultura familiar: primeiros olhares e oportunidades de ação no Tocantins.

Nos últimos anos a piscicultura vem se consolidando como atividade de destaque no sistema de produção da agricultura familiar. A visão dos produtores sobre a atividade vem se modificando, deixando de ser uma atividade marginalizada na propriedade e se tornando uma alternativa de diversificação da produção. Contudo, o acesso dos produtores à extensão aquícola ainda é deficiente. O acesso às tecnologias ainda é considerado um elemento fraco na cadeia produtiva da aquicultura, sobretudo na piscicultura familiar. Apesar destes gargalos, a produção piscícola oriunda da agricultura familiar tem aumentado significativamente nos últimos anos, em especial no estado de Tocantins. O crescimento da piscicultura familiar neste estado levou a Embrapa Pesca e Aquicultura a desenvolver uma ação denominada Projeto Divinópolis, que visa identificar demandas e propor ações relacionadas à geração de tecnologias para a piscicultura familiar, além de fornecer subsídios para políticas públicas e ações de fomento. Tais ações vislumbram o fortalecimento da cadeia produtiva da piscicultura nos municípios de Divinópolis e Abreulândia, área de abrangência do projeto.Organizado por: Sílvio Ricardo Maurano; AQUACIÊNCIA 2012

Sôbre uma modificação no método de Neubauer

O presente trabalho relata os dados obtidos, segundo uma modificação do método de Neubauer, comparados aos obtidos pelo método usual do citado autor. A modificação consistiu no uso de cristalizadores menores e no emprêgo de um número de plantas e de um pêso de terra muito menores. Assim, foram colocadas 25 sementes de arroz em 20 g de terra, intimamente misturadas com 40 g de areia de praia lavada, em cristalizadores de 80 mm de diâmetro, por 20 mm de altura. Decorridos 18 dias após a germinação, as plantas foram colhidas, incineradas e o potássio foi determinado por fotômetro de chama. Os resultados foram comparados com os dados obtidos através de um experimento feito com as mesmas amostras de terra e no mesmo tempo, conforme a técnica usual de Neubauer. Praticamente, os dois métodos se equivalem, conforme mostram os dados do quadro 1 em Resultados e Discussão. As principais vantagens do método modificado, em relação ao método usual de Neubauer, podem ser resumidas nas seguintes: redução do pêso da amostra de 100 para 20 g e redução do pêso da areia de praia lavada de 350 para 70 g; redução da área ocupada pelos cristalizadores para menos de um terço; redução do número de plantas para um quarto (de 100 para 25 plantas) e redução do trabalho exigido para a execução do método, desde o preparo dos cristalizadores, até o preparo das plantas, incineração e análise.A MODIFICATION OF THE NEUBAUER'S METHOD This paper reports the data obtained, from a modification of the Neubauer method, as compared to the data obtained from the original one. The modification consistec of using smaller crystallizing dishes, and both a very small number of seedling and weight of soil. Thus, there were seeded 25 rice grains in 20 g of soil, very well mixed with 40 g of beach washed sand, in crystallizing dishes having 8C mm in diameter and 20 mm in height. Eighteen days after germination, the seedling were pulled out, their roots washed dried, ashed and its potassium determined by the flame photometer method. The results were compared with the data obtained from an experiment carried on with the same soil samples, at the same time, according to the usual Neubauer technique. Both methods are practically equivalent, as can be seen from the data on Table I in Results and Conclusions, in the Portuguese text. The main advantages of the modified method over the usual Neubauer method may be summarized as follows: reduction of both the soil sample weight from 100 to 20 g and the washed sand from 350 g to 70 g; the room taken by the crystallizing dishes is less than one third; the number of seedlings is reduced to one forth (from 100 to 25) and it takes less work for the handling of the experiment in all its steps

Tillage system effect on the epidemic of soybean brown spot.

Six field experiments were carried out during the summers of 1997 to 2003 to evaluate disease progress of soybean brown spot caused by Septoria glycines considering two tillage systems, conventional and no-tillage (wheat was cultivated during winter in all plots). Two logistic models were fitted to the disease progress data: (i) a logistic model with constant disease progress rate r [y=1/(1+(1/y0-1)exp(-rt)), where y0 is the initial disease level at time t=0] and (ii) a logistic model with an exponentially increasing progress rate r(t)=r0 ebt [y=1/(1+(1/y0-1) exp(r0/b(1-ebt))), where r0 is the initial progress rate at time t=0, b the rate increasing parameter, and y0 again the initial disease level]. The logistic model with constant rate underestimated disease incidence on the first disease assessment in nine out of twelve epidemics. The logistic model with an increasing rate gave a better fit to all disease progress curves (R2 between 0.90 and 0.99; no pattern in the residuals). According to this model, y0 was in most cases (four out of six) significantly smaller in the plots with no-tillage compared with conventional tillage, but no differences were detected in the initial rate parameter r0 and the rate increasing parameter b (with one exception). It is proposed that these results are due to higher susceptibility of old leaflets compared with young leaflets, as demonstrated by artificial inoculation: In four laboratory experiments the mean brown spot severity was 16.7 % on old leaflets but only 3.9 % on young leaflets

Estudos sobre a nutrição mineral do feijão macassar (Vigna sinensis (L) Endl.). V: chave para a identificação de deficiências minerais

Symptoms of deficiency of macro and micronutrients were induced in Vigna sinensis by growing two cultivars in nutrient solution under the necessary treatments. Results there of were used to prepare a key which could be used in the visual diagnosis of mineral deficiencies. As a rule, the information obtained is in agreement with result found in the literature for other legumes. It is noteworthy, however, that symptoms of Mo and Zn first showed up in older leaves.É apresentada uma chave para identificação visual das deficiências de macro e de micronutrientes em Vigna sinensis

Estudos sobre a nutrição mineral do feijão macassar (Vigna sinensis (L) Endl.). I: deficiências minerais

Sintomas de deficiências de macro e micronutrientes foram induzidos nas variedades de Vigna sinensis "pitiúba" e "dorminhoco* cultivando-as em solução nutritiva com omissão de um elemento de cada vez. Embora os sintomas, de modo geral, concordem com os descritos na literatura para outros feijões, observou-se diferença varietal na susceptibilidade às carências.This paper deals with the results of an experiment designed to induce symptoms of deficiency of macro and micronutrients in two varieties of "cowpea" extensively grown in the Northeast of Brazil, "dorminhoco" and "pitiúba". As a rule, the results show that visual abnormalities found in the test plants agree with those described in the literature for other beans. It seems, however, that both varieties are less sensitive to the omission of S, Cu, and Mo from the substrate

Estudos sobre a nutrição mineral do feijão macassar (Vigna sinensis (L.) Endl.). IV: exigências de macro e micronutrientes

Duas cultivares de Vigna sinensis, "dorminhoco" e "pitiúba" foram cultivadas em solução nutritiva completa ate o fim do ciclo. Nas diferentes partes, vegetativas e reprodutivas, foram determinados os macro e micronutrientes. Os dados obtidos permitiram estimar as exigências de uma população no campo e as quantidades de elementos exportados como produto colhido.Two varieties of Vigna sinensis, "dorminhoco" and "pitiuba", were grown in nutrient solution till the end of the life cycle and then analysed in order to gain information about their needs for macro and micronutrients. The following has been found: (1) both varieties have the same needs; (2) production of 1 ton of beans requires the following quantities of macro (kg) and micronutrients (g): N - 76, P - 4, K - 85, Ca - 50, Mg - 13, S - 6. B - 320, Cu - 20, Fe - 1855, Mn-162, Mo - 7 and Zn - 89. (3) a comparison with data in the literature has shown that Vigna presents a higher demand for B and Fe than soybean

Estudos sobre a nutrição mineral do feijão macassar (Vigna sinensis (L.) Endl.). II: efeitos das carências de macronutrientes no crescimento, produção e composição mineral

Vigna sinensis, varieties "Dorminhoco" and "Pitiúba", was grown in nutrient solution in the presence and absence of macronutrients; leaves (upper and lower) were collected for analysis at the and of the life cyle or when symptoms of deficiency were marked. Variations found in leaf composition agree, as a rule, with what is contained in the literature with regards to other species under the same type of experimental conditions: reduction in concentration in the tissue when the element was absent from the substrate; interionic, counter ion, and dilution effects. The following levels of macronutrients were associated with maximun growth: N=1.97 ± 0.16; P=0.14 ±0.03; K= 3.20 ± 0.36; Ca=5.38 ± 0.41; Mg=0.66 ± 0.14; S=0.15 ± 0.04. As indication of deficiency, on the other hand, the corresponding leaf contents would be: N =1.28 ± 0.13; P = 0.02 ± 0.01; K=0.64 ± 0.10; Ca=1.79 ± 0.24; Mg=0.14 ± 0.05; S=0.05 ± 0.01. Due to the large differences found between foliar composition in the control and the deficient plants it is very likely that under field conditions deficiencis may occur when the level of a given element in the leaves is higher than those presented herein. Dry matter was affected in the following decreasing ords: Complete, -S, -Mg, -P, -K, -Ca, -N; therefore, the lowest yield was obtained in the treatment lacking nitrogen.Foram induzidas deficiências de macronutrientes em duas cultivares de Vigna sinensis cultivadas em solução nutritiva. A determinação da matéria seca das diferentes partes permitiu verificar o efeito da falta de um nutriente no crescimento e na produção. As análises minerais forneceram indicações que ajudam na avaliação do estudo nutricional