Luadir Gasparotto

Occurrence of lotaustralin in the genus Hevea and changes of HCN-potential in developing organs of Hevea brasiliensis

Abstract The mean HCN-potential (HCN-p) of freshly collected seeds of Hevea brasiliensis is 104.8 μmol HCN per g dry weight. More than 90% of the cyanogenic compound is stored in the endosperm. During seedling development under aseptic conditions HCN-p of the entire seedling decreases to 15% within 19 days. The cyanogenic compounds are metabolized during germination to form noncyanogenic substances. Leaves of H. pauciflora, H. benthanaana, H. pauciflora x H. guianensis and H. spruceana contain both linamarin and (R)-lotaustralin, whereas lotaustralin was not detectable in leaves and seeds of H. brasiliensis.

Análise de risco das mudanças climáticas globais sobre a sigatoka-negra da bananeira no Brasil

O conhecimento dos provaveis impactos das mudancas climaticas globais sobre a ocorrencia de doencas de plantas e de grande importância para o setor agricola, pois permite a elaboracao de estrategias de controle. O presente trabalho teve por finalidade estudar os possiveis impactos das mudancas climaticas sobre a sigatoka-negra da bananeira, por meio da elaboracao de mapas de distribuicao da doenca confeccionados a partir dos cenarios disponibilizados pelo IPCC. Os mapas mostraram que havera reducao da area favoravel a doenca no pais. Tal reducao sera gradativa para as decadas de 2020, 2050 e 2080 e de forma mais acentuada no cenario A2 que no B2. Apesar disso, extensas areas ainda continuarao favoraveis a ocorrencia da doenca, especialmente no periodo de novembro a abril.

Esporulação de Mycosphaerella fijiensis em diferentes meios de cultura

The conidial production of Mycosphaerella fijiensis (isolate LPM472) was evaluated on seven culture media (potato dextrose agar, V8 agar, V8 CaCO3 agar, coconut water agar, potato carrot agar, banana leaf extract agar and mycophil) under four different light exposure regimes (continuous darkness, 12-hour photoperiod, continuous light and ten days under continuous darkness followed by five days of continuous light). The experiment was arranged using a completely random factorial design with five replications with factor A being the four light regimes and factor B being the seven types of media. An erlenmeyer flask (125 ml) containing 20 ml of culture media and 0,5 ml of conidial suspension (5 x 104 conidia/ml) was considered as an experimental unit incubated at 25 oC + 2 oC for 15 days. Sporulation was quantified by counting the number of conidia in a Neubaeur chamber. No sporulation was observed under continuous darkness or for the banana leaf extract agar. Under the 12-hour- photoperiod regime, only mycophil and V8 CaCO3 agar provided sporulation while under continuous light, leave in mycophil resulted in sporulation. The best conidial production was obtained on PDA and V8 CaCO3 agar under the ten days of continuous darkness followed by five days of continuous light regime.

Eficiência de desinfestantes na erradicação de conídios de Mycosphaerella fijiensis aderidos à superfície de bananas

The conidia of Mycosphaerella fijiensis the causal agent of black sigatoka in banana (Musa spp.) can be disseminated over long distances when attached to substrates like cloth and boxes. The aim of this work was to select of effective chemicals for inhibiting conidial germination. The chemicals tested were benomyl, ammonium quaternary, digluconate of chlorhexidine, formaldehyde, pepper essential oil, Ecolife-40, thiabendazol and sodium hypochloride, using the concentrations of 1, 5, 10, 25, 50 and 100 mg/l for each one. For each concentration tested, 1 ml of a conidial suspension (105 conidia/ml) of M. fijiensis isolate LPM472 grown on PDA for the tests, was transferred into test tubes filled with 1 ml of the above chemicals. After 30 h of incubation at room temperature, 100 conidia were observed using light microscope and only germinated conidia were counted. The results show that germination was completely inhibited by ammonium quaternary, benomyl, Ecolife-40 and thiabendazol at 100 mg/l. The same chemicals were also effective when fruits collected from an infected area, were treated by pulverization or immersion techniques (100 and 200 mg/l).

Sobrevivência de conídios de Mycosphaerella fijiensis em diferentes materiais

An experiment was conducted with the objective to determine the survival period of Mycosphaerella fijiensis on common long distance dispersal materials: iron, wood, plastic, cotton textiles, fruits and leaves of banana (Musa sp.), rubber (tires) and cardboard packing. Conidia of M. fijiensis produced on PDA were atomized onto materials. The infested materials were placed in rooms with and without air conditioning systems and in a shed. Conidium survival was evaluated zero, one, three, five, seven, ten, 13, 18, 23, 30 and 60 days after infestation by collecting conidia, plating them and incubating at 25 oC. Conidium germination was quantified by microscope 24 h after incubation. The results showed that the conidia remained viable on leaves and cotton textiles until the last evaluation. The viability of M. fijiensis on cardboard, wood, plastic and tires surfaces was detected up to 30 days after infestation. On fruits and iron, conidia remained viable until 18 days and ten days after infestation, respectively.

First report of black-sigatoka in the State of Minas Gerais, Brazil.

First Report of black-sigatoka in the State of Minas Gerais, Brazil Back-sigatoka caused by Mycosphaerella fijiensis is the most economically important disease of banana (Musa spp.) and plantain. Mycosphaerella fijiensis causes early defoliation resulting in yield losses of about 100% in common bananas such as Prata, Prata Ana and Cavendish cultivars. Black-sigatoka has been occurring in the State of Minas Gerais since July 2004. A sigatoka-negra causada por Mycosphaerella fijiensis Morelet anormorfo Paracercospora fijiensis (Morelet) Deighton, e a doenca mais destrutiva da bananeira (Musa spp.) e platanos. A doenca causa morte prematura das folhas com reflexos significativos na producao; podendo atingir, nas cultivares dos subgrupos Prata e Cavendish, perdas de 100%, a partir do primeiro ciclo produtivo. A identificacao da doenca foi processada com base nos sintomas em folha das cultivares Prata, Prata Ana, Nanica e Nanicao e exames ao microscopio otico confirmando-se a presenca do fungo P. fijiensis nas lesoes ou manchas foliares. Os conidioforos de P. fijiensis sao produzidos isoladamente ou em pequenos grupos, dois a oito, sao retos ou ligeiramente curvos, coloracao clara a marrom-claro, com zero-cinco septos, frequentemente geniculados; raramente ocorre ramificacao na base e apresentam cicatrizes do esporo proeminentes, e medem 16,5 6,25 μm x 4 7 μm. Os conidios sao predominantemente obclavados a obclavados cilindricos, retos ou curvos, hialinos a claro-olivaceos, com um a dez septos, mais comumente cinco septos e apresentam hilo basal conspicuo (Frossard, P. Fruits, vol 35, n 9, 1980). Nas folhas a doenca e caracterizada pelo surgimento de estrias de coloracao marrom-claro na face abaxial que se expandem radial e longitudinalmente, adquirem coloracao marromescura a negra e se transformam em manchas de formato irregular (Figura 1) e, diferentemente do que ocorre na sigatoka-amarela, nao ocorre necrose no limbo foliar nos sitios de infeccao. A coalescencia de varias manchas induz a morte prematura das folhas. A doenca foi identificada nos municipios de Cristina, Sao Jose Alegre, Goncalves e Pirangucu, no Sul de Minas e Coronel Pacheco, zona da Mata Mineira. 04149 FIG.1 Sintomas caracteristicos da sigatoka-negra em folha de bananeira (Musa spp.). NOTAS FITOPATOLOGICAS / PHYTOPATHOLOGICAL NOTES

Reaction of cassava leaves to Microcyclus ulei, causal agent of South American leaf blight of rubber tree

Young cassava (Manihot esculenta) leaves inoculated with conidiospores or treated with an autoclaved conidiospore suspension of Microcyclus ulei, a pathogen to several species of the genus Hevea, react strongly with induction of blue fluorescing compounds in the contact areas, demonstrating local cell growth and irregular tissue formation, leaf distortion and, occasionally, leaf abscission. Restricted hyphal growth also occurs in areas inoculated with living spores, but without formation of new conidiospores. The plant reaction resembles a complex resistance reaction to a biotrophic pathogen rather than a typical non host defense reaction.

Fungos micorrízicos arbusculares em seringueira em latossolo amarelo distrófico da amazônia ocidental

The infection roots with arbuscular mycorrhizal fungi (AMF) can increase the efficiency in growth and nutrients uptake of plants. With the objective to verify this effect, the degree of colonization in rubber tree plantation cultivated in a Xanthic Ferralsol (dystrophic Yellow Latosol) and the efficiency of six AMF in colonization, growth and nutritional status of rubber tree seedlings were evaluated, with three and six months of transplanting. The results showed a low level of mycorrhizal infection and number of spores in adult rubber tree. Six months of transplanting of rubber tree seedlings were sufficient detectable AMFs infection. There was no increase in height, diameter and number of leaves. The foliar nutrients concentration (N, P, K, Ca, Mg, Cu, Fe, Mn and Zn) were also not influenced by the number of spores and infection degree, with only differences by age of the plants (three and six months of transplanting).

Heliconia psittacorum: hospedeira de Mycosphaerella fijiensis, agente causal da sigatoka-negra da bananeira

In Manaus Amazon, Brazil, in September 2003, spots on leaves of Heliconia psittacorum were observed that were very similar to those of black sigatoka caused by Mycosphaerella fijiensis on Musa spp. The pathogen was isolated and a pathogenicity test was done. An isolate from H. psittacorum and other from banana (Musa spp.) cv. Prata Ana were inoculated on H. psittacorum as well as on banana cv. Prata Ana. In both species the tests were positive. Microscopic observations and the results of pathogenicity tests showed that H. psittacorum is another host of M. fijiensis. This is the first report of M. fijiensis on H. psittacorum.

Primeiro relato de mancha foliar em Cedrela odorata causada por Pseudobeltrania cedrelae

A disease causing leaf spot and defoliation on Cedrela odorata trees planted in an Embrapa experimental area near Manaus, Brazil, is first reported here. Lesions start as yellow halos surrounding small light-brown points. Later, necrotic brown lesions are observed exhibiting many black small structures in the central portion, corresponding to fructifications of Pseudobeltrania cedrelae and Colletotrichum gloeosporioides. When P. cedrelae was inoculated the leaf disease was reproduced.