está concentrada no Sul do Brasil. O cereal vem sendo introduzido paulatinamente na região do Cerrado, sob irrigação ou sequeiro (Embrapa 2007). Desde dezembro de 2003, o Estado de Mato Grosso está oficialmente incluso no zoneamento agrícola do Ministério da Agricultura, Pecuária e Abastecimento (MAPA), por meio da Portaria 131, a qual estabelece o plantio de trigo sequeiro entre 1º e 29 de fevereiro, em regiões com altitude igual ou superior a 750 m, e o plantio irrigado entre 21 de abril e 20 de maio, em municípios com altitude superior a 600 m (Brasil 2003).
In recent years, Corynespora leaf blight is on the increase in cotton and has become an important disease in the State of Mato Grosso, Brazil. It attacks several plant species including soybean. It is not yet known whether the same strain of this pathogen attacks both the crops. The objectives of the present investigation were to verify the genotypic and phenotypic variation between the isolates attacking cotton and soybean and to verify the sources of resistance in cotton. Differential response of 23 cotton genotypes was studied under glasshouse conditions using mixture of two randomly selected isolates of C. cassiicola of cotton in equal proportion. Genotypic variation among three cotton and two soybean isolates was studied using ERIC/REP-PCR and rDNA molecular techniques. With one exception, all the cotton genotypes tested so far were susceptible to C. cassiicola isolates of both cotton and soybean. Similarly, results of both molecular techniques indicated that the C. cassiicola isolates attacking cotton and soybean belong to the same strain of the pathogen in Brazil. Since Corynespora blight is a newly immerging disease of cotton and soybean in Brazil, integration of crop rotation and the sanitary practices are suggested to manage the disease.
O pinhão-manso (Jatropha curcas L.) é uma planta oleaginosa tropical e bem adaptada a diversas regiões do Brasil, sendo seu plantio incentivado, nos últimos anos, como alternativa ao fornecimento de matéria-prima para a fabricação de biodiesel. Adicionalmente à capacidade de produzir óleo vegetal, a planta é tolerante ao déficit hídrico, menos exigente em nutrientes e apresenta capacidade de recuperação de áreas degradadas, por possuir raízes profundas e que crescem em solos de baixa fertilidade (Teixeira 2005).Devido às suas vantagens, verifica-se crescente demanda por sementes de boa qualidade fisiológica e sanitária, e, para isto, deve ser avaliada a ocorrência de patógenos nas mesmas. A semente de pinhão-manso é constituída por tegumento (25%) denso e escuro, envolvendo o embrião (75%), rico ABSTRACT RESUMOem óleo. Apresenta, ainda, pequena variação de tamanho e densidade, sem problemas de dormência (Shepetina & Sevast'yanova 1986). Inúmeros danos podem ser provocados por patógenos associados a sementes, dentre eles, a morte em pré-emergência, podridão radicular, tombamento de mudas, manchas necróticas em folhas, caules e frutos, deformações, como hipertrofias e subdesenvolvimento, descoloração de tecidos, infecções latentes e outros (Neergaard 1977). Outros danos podem ser provocados na própria semente, como podridão e perdas do poder germinativo. Para culturas agronômicas, estes danos resultam em redução do stand e da produtividade (Machado 1988). Assim, a semente contaminada ou infectada é um dos meios mais eficientes de introdução, disseminação e acúmulo de inóculo de patógenos, em áreas de cultivo (Neergaard 1977), além de ser eficiente meio de
Ramularia blight, caused by Ramularia areola, is one of the most important diseases affecting cotton crop in Brazil. For its effective control, 5-9 fungicide applications on susceptible cultivars are necessary. The aim of the present study was to evaluate, in vitro and in vivo, the sporulation potential of R. areolaisolates from different Brazilian regions at distinct temperatures. Spore production was assessed in the laboratory and under green house conditions by using leaves from plants of eight cotton cultivars. The in vitro results indicated that the potential of spore production was dependent on temperature. Maximum sporulation of the fungus occurred at 17°C for isolates from São Paulo State and 23°C for isolates from Goiás and Mato Grosso States. In the in vivo study, there was a variation in spore production according to the cultivar and the isolate. Most isolates showed to be highly aggressive on cultivars FM966 LL and DELTAOPAL. The obtained results suggest a more rational use of fungicides and cultivars with decreased fungal sporulation and can form the basis for further studies of the pathogenic variability of this fungus in cotton crops in Brazil. This is the first report on the sporulation potential of Brazilian R. areola isolates.
Cotton blue disease (CBD) is the viral disease which poses the greatest threat to cotton in Brazil. One efficient way of controlling this disease is by using resistant cultivars. However, the recent emergence of an atypical form of CBD (ACBD), caused by a new virus genotype capable of overcoming these resistant cultivars, is causing concern. Thus, the aims of this study were to evaluate the distribution of ACBD in the states of Mato Grosso (MT) and Goiás (GO), to determine the relationship between vector infestation level, disease incidence and yield, and to check the reaction of cotton cultivars to two viral isolates. In both cotton production areas, 1128 plots were surveyed and 6.5% showed plants with the virus, 97.3% and 2.7% with ACBD and CBD, respectively. In cultivars susceptible to ACBD, a positive linear relationship between changes in the levels of aphid infestation and incidence of viral infection was indentified, and a negative linear relationship between infestation level and yield. The maximum acceptable level of aphids up to 80 days after sowing for susceptible cultivars was approximately 15%. Although 83% of the cultivars were shown to be resistant to CBD, only 19.2% were resistant to ACBD. There was also a number of cultivars with considerable resistance to both isolates.
The aim of this work was to investigate the feasibility of using a water restriction technique with osmotic solutes to control sunflower (Helianthus annuus L.) seed germination in blotter tests. The effects of water potential (-0.8 MPa -Megapascal, -1.0 MPa, -1.2 MPa and -1.4 MPa) of substrates osmotically modified with sodium chloride or mannitol were evaluated for seed germination, radicle length and mycoflora present in the samples. The effects of levels of osmotic potentials ranging from -0.35 MPa to -1.4 MPa were also investigated on mycelial growth of the fungi Alternaria alternata and Alternaria zinniae on PDA medium. All osmotic potentials were able to inhibit or to retard seed germination to the extent that seed examination in stereomicroscope became easier without affecting seed mycoflora associated with the seeds. Mycelial growth of A. alternata was stimulated by all osmotic solutes tested, while mycelial growth of A. zinniae was stimulated by mannitol and reduced by all NaCl osmotic potential levels used. Key words: Helianthus annuus, sodium chloride, mannitol. RESUMO Uso de solutos osmóticos na inhibição da germinação de sementes de girasol em testes de sanidade ("blotter test")Neste trabalho, o objetivo foi avaliar o uso de solutos osmóticos em testes de sanidade de sementes de girassol pelo método de incubação em papel de filtro com restrição hídrica do substrato, induzida pela adição de cloreto de sódio e manitol, em relação à germinação de sementes, comprimento de radícula e a detecção da micoflora associada às sementes ou plântulas. Foram testados os níveis de restrição hídrica de -0,8 MPa (Megapascal), -1.0 MPa, -1,2 MPa e -1,4 MPa. O crescimento micelial in vitro dos fungos Alternaria alternata e Alternaria zinniae foi também avaliado em meio de BDA osmoticamente modificado com os mesmos solutos e níveis de restrição, variando de -0,35 MPa (BDA padrão) a -1,4 MPa. A restrição hídrica do substrato de papel induzida pelos solutos testados, nos níveis avaliados, reduziu a germinação das sementes e o comprimento de radícula e não interferiu na detecção dos fungos. A restrição hídrica do meio BDA, induzida por manitol nos diferentes potenciais osmóticos testados, estimulou o crescimento micelial tanto de A. alternata quanto de A. zinniae, enquanto que o meio modificado com NaCl estimulou apenas o crescimento micelial de A. alternata, afetando adversamente o crescimento micelial de A. zinniae. Palavras-chave: Helianthus annuus, cloreto de sódio, manitol.
A sigatoka-negra, causada pelo fungo Mycosphaerella fijiensis, pode causar 100% de perdas na produção das cultivares suscetíveis. O objetivo deste trabalho foi avaliar o progresso da sigatoka-negra em bananeiras após a emissão do cacho no Município de Cáceres, Mato Grosso. O experimento foi conduzido no período de fevereiro a dezembro de 2004 em plantios das cultivares Grande Naine, Maçã e Farta Velhaco, sendo esta última uma cultivar de plátano, do grupo Terra. As avaliações foram efetuadas a intervalos de 15 dias, quantificando-se, através de uma escala diagramática, a severidade da sigatoka-negra em todas as folhas de 5 plantas de cada cultivar, marcadas logo após a emissão das inflorescências. A partir dos dados coletados no campo, computaram-se: a severidade da doença na folha n.º 10 e o número de folhas viáveis. Considerou-se como folha viável as folhas sadias e aquelas com até 15% de área foliar lesionada. Os dados de temperatura e da umidade relativa foram registrados por um aparelho eletrônico instalado na área. A precipitação pluvial foi registrada na Estação meteorológica de Cáceres, distante 12 km do experimento. As condições climáticas foram favoráveis à sigatoka negra durante o ano todo e as plantas das cultivares Grande Naine, Maçã e Farta Velhaco após a emissão do cacho, perderam totalmente as folhas antes dos frutos atingirem o pleno desenvolvimento, cujos prejuízos no primeiro semestre atingiram 100% de perdas na produção comercializável.
The factors that influence the ability of cotton to minimize yield loss despite parasitism by Rotylenchulus reniformis (i.e., tolerance) were evaluated for 12 cotton genotypes. Reproduction of R. reniformis and total length of the root system were measured under greenhouse conditions, and the relationship of those variables to yield loss caused by R. reniformis in infested fields was evaluated. Values for nematodes per gram of root and root length were standardized by setting the genotype with greatest value as 100% and then calculating a percentage for each genotype. There was significant variability among genotypes in yield loss, resistance, and root length. Average yield loss for the genotypes ranged from 10.4% for IAC 26RMD to 43.2% for IMACD 5675B2RF. The least nematode reproduction was on IAC 26RMD, which had 49.6% of the reproduction on the susceptible check, Deltapine 16. The genotype with the shortest total root length was 34% less than the genotype with the greatest length. There was a significant linear relationship between percentage yield loss caused by R. reniformis and root length and nematodes per gram of root, both expressed as a percentage of the maximum, represented by the following equation: Yield loss (%) = 16.1258 – 0.1918*(% maximum root length) + 0.3728*(% maximum eggs + vermiform/g of roots). We conclude that tolerance to R. reniformis in cotton is influenced by the size of the root system and the parasitic load on the plant (nematodes per gram of root). Management approaches that increase root growth may lower the parasitic load, thereby reducing losses in cotton to R. reniformis.
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