Jefferson Luis da Silva Costa

Biological control of Phytophthora root rot of avocato with microorganisms grown in organic mulches

Organic mulches colonized with microbial biocontrol agents, termed bioenhanced mulches, were tested for their ability to reduce Phytophthora root rot of avocado (Persea americana Mill.). Benomyl-resistant mutants of Gliocladium virens (KA 230-1) and Trichoderma harzianum (KA 159.2) isolated from suppressive soils and selected as efficient antagonists of P. cinnamomi were evaluated for their ability to colonize different mulches under controlled laboratory conditions. Sudangrass and a coarse yardwaste were found to be better substrates than a fine yardwaste, woodwaste or rice hulls for biocontrol agents propagules production. The most suitable conditions for colonization were an optimum temperature of 24°C, a moisture content of 20% for sudangrass and 30% for the coarse yardwaste, and a continuous light exposure during a 15-day incubation period. In the greenhouse, fresh sudangrass and a coarse yardwaste colonized with G. virens and used as a surface mulch proved to be the best combination for reducing the population of P. cinnamomi in 4-liter pots containing artificially-infested soil. Healthy avocado roots made up 31-37% of the roots in the G. virens-mulch combinations compared to 0% healthy in infested controls after two months.

Armazenamento de sementes de feijão revestidas com polímeros e tratadas com fungicidas

Abstract – Coating seeds with polymers associated with chemicals is used to promote a better fixation of seedtreatment products, and therefore minimizing toxic hazards. The objective of this work was to verify the effect offour-month storage on quality of dry bean ( Phaseolus vulgaris L.) seed coated with polymers, and treated withfungicides. Bean seeds were inoculated by immersion in a suspension of Colletotrichum lindemuthianum (5x10 5 conidia/mL), applied under vacuum. After the inoculation, seeds were treated with different types offungicides: wettable powder, dry powder and concentrated suspension, applied either mixed or prior to polymercoating. Two different types of PVA paint were used as coating agent. Seed quality was evaluated throughgermination, vigor and pathological tests. Germination of coated and treated seeds was not affected during thestorage period. The association of coating and a wettable powder treatment showed a higher germinationpercentage after two months of storage. The formulations wettable powder and concentrated suspensionpromoted a better control of the pathogens.Index terms:

Relações entre atributos do solo e atividade de formigas em restingas

In restinga soils with sand-quartzous constitution the influence of the organic fraction and biological activity on soil key functions is increased, e.g., the capacity of recycling and storing nutrients. The analysis of soil attributes and edaphic fauna at sites under different vegetation cover types is important to understand the behavior of these environments. In this study, chemical, physical and microbiological soil attributes of restinga sites and their relationships with ant populations under different vegetation types in the state of Sergipe were evaluated. Samples of six vegetation types (three sites per cover) were collected, four of which in the area of Caju (forest, ginger-grass, coconut palm plantation and brushwood) and two in the area of Pirambu (dune plateau forest and dune footslope forest). Chemical attributes were analyzed in samples collected from the layers 0-5 and 5-20 cm and the microbial activity evaluated by hydrolysis of fluorescein diacetate, in samples collected from the 0-10 cm layer. The organic fragment mass was evaluated at different depths. Ant communities with activity on the soil surface were considered for evaluation. The principal component analysis was used to compare the sites. The organic compartment attributes (organic C, dissolved organic C and organic fragments) were very sensitive to modifications in the vegetation cover at Caju sites, isolating the native forest sites from the disturbed ones and the ginger-grass site from the coconut palm and brushwood sites. Soil solution attributes influenced by sea-salt spray (electric conductivity, K, Na and Mg) distinguished the Pirambu from the Caju sites. The ant groups had a high level of specialization. Canonical correspondence analysis indicated a low percentage of variance of distribution of these groups and isolated the forest sites from other uses, indicating the existence of other attributes to be considered for distribution.

Efeito do armazenamento na compatibilidade de fungicidas e inseticidas, associados ou não a um polímero no tratamento de sementes de feijão

The compatibility of chemical products in dry bean seed coating associated to a polymer was studied in this work. Also, the maximum period of storage for these seeds coated with polymer and defensives was established. Dry beans, from cv. Perola were submitted to the following treatments: 1) control; 2) carbendazin + thiram + fipronil + polymer; 3) carbendazin + thiram + fipronil; 4) carbendazin + thiram + thiodicarb + polymer and 5) carbendazin + thiram + thiodicarb. The evaluated parameters included emergency, lesser cornstalk borer (Elasmopalpus lignosellus) efficiency control and seed pathology. For the parameters emergency and borer control the best results were obtained with the treatments including fipronil insecticide. As for seed pathology, treatments with thiodicarb insecticide were more efficient, indicating a suitable compatibility of this insecticide with the fungicides carbendazin + thiram until 150 days of storage. The products tested could be used in dry bean seed dressing, and the treated seeds could be stored up to hundred and twenty days prior to planting.

Avaliação da resistência de cultivares e linhagens do feijoeiro comum a diferentes populações de Uromyces appendiculatus

A tecnica de folhas destacadas tem sido utilizada para estudos relacionados a doencas de plantas. Neste trabalho foi utilizada a tecnica de folhas de feijoeiro (Phaseolus vulgaris) destacadas e cultivadas em vermiculita, visando estudar a resistencia de diversas cultivares a diferentes populacoes de Uromyces appendiculatus, coletadas em diferentes regioes ou epocas. Compararam-se os sintomas da doenca na planta com os observados nas folhas destacadas. Os sintomas nas folhas destacadas foram semelhantes aos das folhas nas plantas. As cultivares Novo Jalo, Corrente e Apore de feijoeiro foram resistentes a todas as populacoes do patogeno. A tecnica de folhas destacadas e cultivadas em vermiculita mostrou-se util e vantajosa com relacao as demais tecnicas de avaliacao de resistencia. Por permitir a insercao de varias folhas num mesmo recipiente, facilita a avaliacao de maior numero de cultivares em menor espaco, alem de proporcionar melhor comodidade durante a execucao do trabalho.

Enhancement of soil DNA extraction by the use of a hand held mixer

The efficiency of soil DNA extraction using a bead beater homogenizer (Biospec Products - Germany) was compared to that obtained with a hand held mixer (Moulinex - Brazil). The hand held mixer costs 100 times less and extracted seven times more crude DNA than the bead beater.

Indução de calo a partir de eixo embrionário de coqueiro (Cocos nucifera L.)

Este estudo teve como objetivo avaliar a capacidade de formacao de calos a partir de tecidos originarios do eixo embrionario de embrioes zigoticos de coqueiro (Cocos nucifera L.) em diferentes concentracoes de 2,4-D. O experimento foi instalado em delineamento inteiramente casualizado, em esquema fatorial 4x5 (4 concentracoes de 2,4-D x 5 segmentos do eixo embrionario). Os eixos embrionarios foram excisados longitudinalmente dos embrioes zigoticos e, em seguida, submetidos a assepsia com hipoclorito de sodio (0,2%) por dois minutos, lavados com agua destilada esteril e imersos por dois minutos em solucao de acido citrico esteril (100 mg.L-1). Os eixos embrionarios foram entao seccionados em cinco segmentos correspondentes as posicoes A, B, C, D e E, e transferidos para placas de Petri contendo meio de cultura Y3, suplementado com quatro concentracoes de 2,4-D (10-4; 1,36x10-4; 3,62x10-4 e 4,52x10-4 M), sacarose (50 g.L-1), carvao ativado (2,5 g.L-1) e vitaminas de Morel e Wetmore, mantidos em ambiente escuro, em temperatura de 25 ± 2oC. Apos 15 dias de inoculacao, os segmentos A e B apresentaram 97,5% de explantes com calos friaveis na concentracao de 10-4 M de 2,4-D, e 92,5% e 80%, respectivamente, na concentracao de 1,36x10-4 M. O segmento E, em ambas as concentracoes, apresentou 60% de calogenese. Apos 30 dias de inoculacao, os segmentos A e B apresentaram 100% e 97,5% de calogenese na concentracao de 10-4 M, e 90% e 80%, respectivamente, na concentracao de 1,36x10-4 M. Em ambas as concentracoes, o segmento E apresentou de 55 a 57,5% de formacao de calos. As concentracoes de 2,4-D que melhor induzem calogenese, sao as de 10-4 e 1,36x10-4 M. Os segmentos A, B e E apresentaram maior competencia para calogenese.