Osvaldo Paradela Filho

Gomose da acácia-negra causada por Ceratocystis fimbriata Ell. & Halst.

Several plants of Acacia decurrens showed wilting and subsequent branche drying. The branches showed wood splitting and gum exudation. The transversally cut wood showed ashy colored pith, that desenvolved numerous perithecia when kept in a humid chamber. These perithecia were transferred aseptically to potato-dextrose-agar and the culture was classified as Ceratocystis fimbriata Ell. & Halst. Four mounth old Acacia plants inoculated with the isolate died after 14 days. The fungus was again isolated from these dead plants. Cross inoculation tests with isolate of C. fimbriata from Acacia and mango (Mangifera indica L.) showed pathogenic effects for both hosts.

EFEITO DA XYLELLA FASTIDIOSA EM CAFEEIROS EM DIFERENTES REGIÕES EDAFOCLIMÁTICAS (1)

A bacteria Xylella fastidiosa vem causando problemas para a cafeicultura, uma vez que sua presenca, associada a diversos fatores de estresse, provoca um decrescimo na producao devido a diminuicao no numero e tamanho dos frutos e a morte de alguns ramos. Este trabalho objetiva avaliar o efeito da X. fastidiosa sobre cultivares de Coffea arabica (enxertados ou nao) atraves da quantificacao da proporcao de vasos do xilema obstruidos pela bacteria, nas diferentes partes da planta e entre ramos com e sem sintoma da doenca, em experimentos desenvolvidos em diferentes regioes edafoclimaticas. Avaliou-se tambem a distribuicao das classes de infeccao nas diferentes partes da planta nos materiais geneticos estudados. Os experimentos foram instalados em 1986 em Mococa e Garca (SP) e as amostras para o estudo anatomico, retiradas em abril de 1998 e 2000 (periodo de estresse hidrico), respectivamente, das plantas de cafeeiros dessas areas. Na regiao de Mococa, observou-se que a nervura principal e o peciolo foram os tecidos com proporcao maior de vasos do xilema obstruidos pela X. fastidiosa; na regiao de Garca, foram o peciolo e o caule. Nao houve diferencas significativas na obstrucao de elementos de vaso do xilema do cafeeiro ocasionado pela bacteria entre as duas regioes estudadas. Nao houve tolerância a bacteria nos materiais geneticos, havendo no entanto variacao dentro de cada um deles. Na regiao de Garca, nas plantas de cafe, observou-se alta proporcao de vasos obstruidos nas raizes (3%), entretanto, nao houve dano maior na parte aerea.

COMPARAÇÕES SAZONAIS DO EFEITO DA XYLELLA FASTIDIOSA EM CULTIVARES DE CAFEEIRO (1)

SEASONAL COMPARACTIONS OF XYLELLA FASTIDIOSA EFFECT IN COFFEE CULTIVARS Historically, coffee plants showing atrophy and scorch branch were attributed to nutritional disorders due to successive high yields. The bacteria XylelLa fastidiosa Wells et al. is currently the most reported pathogen related with the problem and the symptoms are associated with stress. Although the bacteria has been well studied in the United States particularly in grape, few is known about the pathogenhost-vector relationship. The present studies were carried out with coffee plants (grafted or not grafted) aiming to evaluate xylem vessels obstruction in various plant parts, including branches with and without

Ocorrência de Serratia marcescens bizio sobre lagartas de Heliothis virescens (Fabr.)

A large quantity of dead worms was observed in rearing of Heliothis virescens. A bacteria, later identified as Serratia marcescens Bizio, was isolated from the dead worms. The present work registers the occurrence and confirms the pathogenicity of S. marcescens on H. virescens.

Tentativa de infestação artificial do solo com Fusarium oxysporum f. sp. vasinfectum em condições de campo

In order to establish an experimental breeding field for Fusarium wilt resistance, in cotton, an area of about 8,000m2 was artificially inoculated with the pathogen twice during the crop season. A total of 14 inoculations was performed along the 7 consecutive years of experimentation. However, taking into account the typical external and internal symptoms exhibited by the plants, the incidence of the diseases was considered low and unsatisfactory, as the final purposes are concerned. The possible causes of the unsuccess, such as climatic conditions, soil texture, method of inoculation, supressiveness of the soil to Fusarium and absence of Fusarium x nematodes interaction, are discussed.