Resumo -O objetivo deste trabalho foi avaliar o efeito nematostático e nematicida de extratos aquosos de bulbilhos de alho (Allium sativum L.), folhas de mandioca (Manihot esculenta Crantz), folhas e sementes de mamão (Carica papaya L.), folhas de hortelã (Mentha piperita L.) e casca de gliricídia (Gliricidia sepium (Jacq.) Steud.) em Scutellonema bradys, agente causal da casca-preta do inhame (Dioscorea cayennensis Lam.). Todos os extratos vegetais inibiram a mobilidade e causaram mortalidade ao fitonematóide. Os extratos de hortelã e de mandioca causaram menos de 45% de mortalidade a S. bradys. As maiores porcentagens de mortalidade são causadas pelos extratos de sementes e folhas do mamoeiro e pelos bulbilhos de alho.Termos para indexação: extratos de plantas, casca-preta do inhame, controle alternativo. Toxicity of plant extracts to Scutellonema bradysAbstract -The objective of this work was to evaluate the nematostatic and nematicide effect of aqueous extracts from garlic bulbs (Allium sativum L.), cassava (Manihot esculenta Crantz) leaves, papaya (Carica papaya L.) leaves and seeds, mentha (Mentha piperita L.) leaves, and gliricídia (Gliricidia sepium (Jacq.) Steud.) tree bark to Scutellonema bradys, the causal agent of yam (Dioscorea cayennensis Lam.) dry rot. All plant extracts inhibited the mobility and caused mortality to S. bradys. Mentha and cassava extracts cause less than 45% mortality to S. bradys. The highest percentages of mortality are caused by extracts from papaya seeds and leaves, and garlic bulbs.
To contribute for the development of environmental friendly methods for weed control, a selection of rhizobacteria able to produce phytotoxic substances was carried out. Initially, 35 strains previously isolated from plants in the south of Minas Gerais State (Brazil) were grown in tryptic soy broth. After removal of bacterial cells, the resulting liquids were freeze-dried and extracted with methanol/ethyl acetate (1:1). The extracts were concentrated under vacuum and dissolved in water to be submitted to a lettuce (Lactuca sativa L.) seed assay. Metabolites produced by five strains reduced the number of normal seedlings to values statistically bellow the one observed for the negative control, being the most expressive results obtained with Bacillus cereus Frankland and Frankland, isolated from Ricinus communis L., which was able to cause rotted rootlets to 82.4% of seedlings. The bacterium metabolites also avoided germination of 52% Brachiaria decumbens Stapf seeds and the remaining 48% resulted in abnormal seedlings. Metabolites from B. cereus were submitted to a purification process guided by the lettuce seed assay. As a consequence, one substance causing rotted rootlets to all lettuce seedlings during the seed assay at 0.057 g/L was isolated and will be identified in future studies.
Dez filtrados de culturas de actinomicetos causaram redução na motilidade e 100% de mortalidade de J2 de Meloidogyne javanica. A diluição de alguns causou redução de 75 a 85% de mortalidade. Contudo, o filtrado do isolado PIC 1 causou, mesmo em diluição, 100% de mortalidade. Alguns filtrados reduziram a motilidade sem causar mortalidade. Dos isolados que causaram mortalidade também reduziram eclosão de J2. Entretanto, a porcentagem de redução variou ao longo do período de crescimento do actinomiceto em meio líquido. Exsudatos obtidos de colônias de alguns isolados de actinomicetos crescidos em meio sólido causaram 100% de mortalidade e redução na motilidade de J2 de M. javanica. Os isolados de actinomicetos ALF 4 e QUI 4 produziram substâncias tóxicas a J2 tanto em filtrado quanto em exsudato de colônia.
Management of plant-parasitic nematodes with the use of nematicides has not been recommended for small farmers that grow yam in the Northeastern region of Brazil, due to its high cost and residue toxicity. The use of plants with antagonistic effect to nematodes and green manure which improves soil chemical, physical and biological characteristics can be a viable and low cost alternative to control parasitic nematodes. This work aimed to evaluate the effect of crotalaria (Crotalaria juncea) and pigeon pea (Cajanus cajan) plants on the control of yam nematodes. Three experiments were carried out. The first was conducted under in vitro conditions to evaluate the nematostatic and nematicide effect of extracts from fresh and dry matter of the above ground parts of crotalaria, pigeon pea, and the combination of both. The second experiment was carried out under greenhouse conditions to evaluate the effect of soil amendment with crotalaria, pigeon pea, and the combination of both in the infectivity of Scutellonema bradys, using tomato plants as the host plant. The third experiment was conducted under field conditions to evaluate the effect of crotalaria, pigeon pea, and the combination of both, cultivated between yam planting rows and incorporated to soil surface, on yam nematodes. The aqueous extract obtained form fresh matter of crotalaria had a nematicide effect of 100% for S. bradys. Extracts from dry matter of both crotalaria and pigeon pea did not have any nematicide effect, but had a nematostatic effect. Incorporation of crotalaria to soil inhibited infectivity of S. bradys in tomato seedlings. These results showed that planting crotalaria alone or in combination with pigeon pea, between the yam planting rows, is an efficient method for controlling S. bradys and Rotylenchulus reniformis associated with yams. Crotalaria can be used for controlling these plant-parasitic nematodes in soil.
O trabalho teve o objetivo de avaliar as populações de fitonematóides associados à cultura da mandioca, plantada em sucessão à cultura do inhame, em 22 propriedades rurais do Recôncavo da Bahia. Adicionalmente, foram feitos testes de hospedabilidade com as variedades de mandioca 'Cigana' e 'Talo Roxo', ao nematóide Scutellonema bradys. Foram constatadas as presenças dos seguintes nematóides: Pratylenchus brachyurus, Scutellonema bradys, Meloidogyne incognita e Rotylenchulus reniformis, nas raízes e amostras de solo. Além dos nematóides, Tylenchus sp., Aphelenchus sp., Meloidogyne incognita, Mesocriconema sp., Aphelenchoides sp., Helicotylenchus presente apenas nas amostras de solos. O teste de hospedabilidade demostrou que as variedades de mandioca estudadas não são hospedeiras de Scutellonema bradys.
Conventional cotton production in western Bahia, Brazil, involves intensive use of agricultural inputs and mechanization, which may affect arbuscular mycorrhizal fungi (AMF). This work aimed at studying the impact of conventional and organic cotton production in the AMF of western Bahia. Soil samples were obtained from conventional white cotton and colored cotton organic production systems as well as from native Cerrado areas, close to the white cotton fields, and from the subcaducifolia vegetation, close to the organic colored cotton farms. The most frequent species in the conventional farming areas belonged to the genera Acaulospora (10 spp.); Glomus (8 spp.); Dentiscutata (3 spp.); Ambispora, Pacispora and Scutellospora (2 spp. each), as well as Claroideoglomus etunicatum, Diversispora sp., Entrophospora infrequens, Gigaspora sp., Orbispora pernambucana, Paradentiscutata maritima, and Paraglomus occultum. eighteen species were found in the organic farming areas, with the predominance of Glomus (5 spp.) and Acaulospora (5 spp.), and with Claroideoglomus, Dentiscutata, Gigaspora, Corymbiglomus, Orbispora, Paraglomus, Scutellospora, and Simiglomus (1 spp. each). Paraglomus bolivianum was first reported in Cerrado. In the native vegetation, nine species were found, with the predominance of Glomus and Acaulospora. The highest number of AMF species was found in the organic farming areas, which deserves further investigation.
Resumo -O nematoideMeloidogyne enterolobii causa severos danos à goiabeira, sendo um fator limitante à produção. Os fungos micorrízicos arbusculares (FMA) podem prejudicar o desenvolvimento de algumas espécies de nematoides fitoparasitos, reduzindo a ovoposição e o número de galhas no sistema radicular de plantas infectadas. Com o presente trabalho, objetivouse avaliar o potencial de FMA, isolados de solos de cerrado nativo, em reduzir a infectividade de M. enterolobii em mudas de goiabeira. Para tanto, foi conduzido um experimento em casa de vegetação, em blocos casualizados com oito repetições, no qual se avaliou a porcentagem de colonização micorrízica, o número de galhas e de ovos do nematoide citado por grama de raiz, na presença de oito diferentes isolados fúngicos, e a testemunha, sem presença de fungo, em goiabeira. Todos os isolados de FMA oriundos do bioma cerrado foram eficientes na colonização das raízes, reduziram o número de galhas do nematoide e afetaram a reprodução; no entanto, o grau de colonização radicular pelos fungos micorrízicos, isoladamente, não é um indicativo de controle da infectividade desse patógeno, já que alguns isolados que apresentaram maior colonização foram menos eficazes na sua redução, de forma que os isolados de FMA avaliados diferiram quanto à eficiência em reduzir a reprodução de M. enterolobii em mudas de goiabeira. Palavras-chave -Micorrizas. Nematoide das galhas. Psidium guajava.Abstract -The nematode Meloidogyne enterolobii causes severe damage to guava tree, being a limiting factor to production. Arbuscular mycorrhizal fungi (AMF) can impair the development of some species of plant parasitic nematodes by reducing oviposition and the number of galls in the roots of infected plants. The present research aimed to evaluate the potential of AMF, isolated from soils of native savanna, in reducing the infectivity of M. enterolobii in guava tree seedlings. For this purpose, an experiment was conducted in a greenhouse in randomized block design with eight replications, in which we evaluated the percentage of mycorrhizal colonization, the number of galls and eggs of the mentioned nematode per gram of root, in the presence of eight different fungal isolates, and the control without the presence of the fungus, in the guava tree. All AMF isolates from the savanna were effective on root colonization, reduced the number of nematode's galls and affected their reproduction; however, the degree of root colonization by mycorrhizal fungi, alone, is not indicative of infectivity control of this pathogen, since some isolates showing increased colonization were less effective in reducing it, so that the evaluated AMF isolates differed regarding the efficiency in reducing the reproduction of M. enterolobii in guava tree seedlings.
Objetivo: Dentre os nematoides que atacam a cultura do tomateiro, o causador de galhas nas raízes, Meloidogyne spp. é o que apresenta maior ocorrência na cultura. O uso de substâncias de plantas nativas do Cerrado, torna-se uma alternativa no controle da população dessa espécie de nematoide, pois estas plantas podem possuir substâncias com ação nematicida. Diante disso, o objetivo deste trabalho foi avaliar o potencial dos doze extratos obtidos da casca e das folhas de seis árvores nativas do cerrado em controlar e o nematoide Meloidogyne incognita (Kofoide & White) no tomateiro. Métodos: Para montagem do ensaio foram transplantadas mudas de tomateiro da cultivar Santa Cruz Kada, com 30 dias para sacos plásticos contendo substrato composto por areia, solo e composto orgânico (1:2:1) previamente logo após, adicionado 50 ml dos extratos vegetais no substrato infestado. As aplicações dos extratos foram repetidas novamente aos 7, 14, 21, 28, 35 e 42 dias após o transplantio da mudas. Ao término do experimento, o sistema radicular de cada planta foi retirado cuidadosamente e realizada avaliação com a contagem do número de ovos e galhas no sistema radicular do tomateiro. Resultados: Apenas os extratos da casca do Tamboril (E.contortisiliquum) (Vell.) Morong e da folha de Juazeiro (Zizyphus joazeiro Mart.) foram capazes de reduzir significativamente o parasitismo do nematoide no tomateiro.
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