Maria de Lourdes Reis Duarte

In vitro toxin production by Fusarium solani f. sp. piperis

Fusarium solani f. sp. piperis (teleomorph: Nectria haematococca f. sp. piperis), causal agent of root rot and stem blight on black pepper (Piper nigrum), produces secondary metabolites with toxigenic properties, capable of inducing vein discoloration in detached leaves and wilting in transpiring microcuttings. Production of F. solani f. sp. piperis (Fsp) toxic metabolites reached a peak after 25 days of static incubation on potato sucrose broth at 25 oC under illumination. Changes in the pH of the culture filtrate did not alter the effect of toxic metabolites. However, when the pH was changed before the medium had been autoclaved, a more intense biological response was observed, with an optimum at pH 6.0. Isolates that produced red pigments in liquid cultures were more efficient in producing biologically active culture filtrates than those which produced pink coloured or clear filtrates suggesting that these pigments could be related to toxigenic activity. Detached leaves of seven black pepper cultivars and Piper betle showed symptoms of vein discoloration after immersion in autoclaved and non-autoclaved Fsp culture filtrates indicating the thermostable nature of these toxic metabolites.

Three new pathogens infecting antilles cherry in the State of Pará

Em plantios uniformes, a aceroleira (Malpighia glabra) tem sido afetada por doencas que causam manchas e malformacao nos frutos, tornando estes improprios para consumo in natura. A partir de 1999, tres novas doencas caracterizadas pelo aparecimento de manchas foliares e queda da folhagem vem sendo observadas em plantacoes localizadas nos municipios de Santa Izabel do Para e Igarape Acu. Apos isolamento, exame das estruturas morfologicas e testes de patogenicidade em mudas de acerola, os isolados foram identificados como Calonectria ilicicola (anamorfo: Cylindrocladium parasiticum) que causa manchas foliares relativamente grandes atingindo ate 7 cm de comprimento, de coloracao marrom-escura que coalescem atingindo grande extensao da area foliar e causando a queda de ate 50% das folhas; Corynespora cassiicola que provoca manchas necroticas de formato irregular, com bordas marrom-escuras e centro branco, circundadas por um halo amarelo nitido; Myrothecium roridum que causa manchas concentricas de coloracao cinza. O fungo C. cassiicola tem sido relatado causando doencas em varios hospedeiros na regiao amazonica, enquanto C. ilicicola infeta outros hospedeiros, nos Estados do Maranhao e Para.

Resistência de piperáceas nativas da Amazônia á infecção causada por Nectria haematococca f. sp. piperis

The resistance of Piper aduncum, P. arboreum, P. carniconnectivum, P. colubrinum, P. hispidinervium, P. hispidum, P. hostmannianum, P. nigrum, P. tuberculatum and Piper sp. to the infection caused by two Nectria haematococca f. sp. piperis isolates was detected under laboratory and shade house conditions. Due to their high susceptibility, black pepper (Piper nigrum) plants were used as control. When grown in soil infested with the isolate from P. aduncum (Adu), no root rot symptoms were observed on the majority of Piper spp., except on Piper sp. and black pepper. However, in soil infested with the isolate from P. nigrum (Nig) root rot was noticed on black pepper, although not on the other Piper spp. Significant differences (p<0.01) were observed when stems of Piper spp. plants were inoculated with Adu and Nig isolates. On P. nigrum stems typical lesions were followed by yellowish, stem blight and death of plants were observed, while on Piper spp. canker-like tissues around stem lesions were detected, evidencing the high resistance of these related species. These results showed that the isolate from P. aduncum has no ability to colonise Piper spp. root tissues and that at least seven related species are highly resistant to N. haematococca f. sp. piperis. This suggests that these species may be used either as rootstocks or for somatic hybridisation and protoplast fusion in amelioration studies aiming to control Fusarium diseases on black pepper.

Mancha areolada causada por Thanatephorus cucumeris em mogno africano

African mahogany (Khaya ivorensis) introduced in Brazil in recent years has been preferred to reforest devastated areas to replace Brazilian mahogany (Swietenia macrophylla) due to its high-quality timber and its high resistance to Hypsiphyla grandella, the major pest of Brazilian mahogany. Since 1999 a high incidence of target leaf spot caused by Thanatephorus cucumeris has been observed in nursery and in field, in the States of Amazonas and Para (Brazil), causing numerous zonate lesions on mature leaves and 100% leaf fall in seedlings. Young leaves of diseased plants initially show little brown spots surrounded by a purple margin, while in mature plants the lesions are light brown exhibiting concentric rings resembling a target.

Incidence of Fusarium solani in cassava in the State of Pará, Brazil

This paper describes for the first time the occurrence of Fusarium solani infecting cassava (Manihot esculenta) in the State of Para.