Efeito in vitro do extrato etanólico das folhas do melão-de-São-Caetano (Momordica charantia L. ) sobre ovos e larvas de nematóides gastrintestinais de caprinos / In vitro effect of the ethanolic extract of "melão de São Caetano" (Momordica charantia L. ) leaves on the eggs and larvae of gastrointestinal nematodes from goats

O experimento in vitro foi realizado para avaliar a ação do extrato etanólico das folhas do melão-de-São-Caetano (Momordica charantia L.) sobre o desenvolvimento de ovos e motilidade de larvas de nematóides gastrintestinais de caprinos. As larvas foram obtidas de coproculturas e a recuperação de ovos foi feita pela técnica dos quatro tamises, a partir de fezes de caprinos naturalmente infectados da mesorregião do Sertão Paraibano. O extrato foi utilizado nas diluições de 50; 25; 12,5; 6,25 e 3,12 por cento para ambos os testes e como controle positivo e para controle negativo, utilizou-se água destilada estéril. As placas foram examinadas ao microscópio óptico para contagem dos ovos em desenvolvimento e larvas móveis e imóveis, após 24, 48 e 72 horas de incubação. As concentrações do extrato etanólico de M. charantia e os tratamentos controle negativo e positivo diferiram quanto ao número de ovos inviáveis. No teste de motilidade larval as concentrações acima de 12 por cento apresentaram médias significativas quanto ao número de larvas inviáveis. Nas condições ensaiadas a M. charantia apresentou atividade ovicida e larvicida.

The experiment in vitro was performed to evaluate the action of the ethanolic extract of "melão de São Caetano" (Momordica charantia L.) leaves on the development of eggs and motility of larvae of gastrointestinal nematodes from goats. The nematode larvae were obtained from coproculture and the recovery of eggs was done in sieves, from feces of naturally infected goats from the Mesoregion of Paraíba State. The extract was used at the dilutions of 50, 25, 12.5, 6.25 and 3.12 percent for both tests and as positive control; for negative control, sterile distilled water was used. The plates were examined under optical microscope to count the eggs in development and mobile larvae after 24, 48 and 72 h of incubation. The concentrations of M. charantia ethanolic extract and the negative and positive controls differed as to the number of eggs that were not viable. In the larval motility test, concentrations higher than 12 percent had significant means as to the number of larvae that were not viable. Under the tested conditions, M. charantia showed larvicidal and ovicidal activity.

The effect of silicon on the infection by and spread of Pythium aphanidermatum in single roots of tomato and bitter gourd.

The effect of silicon (Si) supply on the infection and spread of Pythium aphanidermatum was studied in the roots of tomato [Lycopersicon esculentum (=Solanum lycopersicum), an Si excluder] and bitter gourd (Mormodica charantia, an Si intermediate accumulator). Individual roots were mounted into PVC compartmented boxes which allowed the application of Si and zoospores to defined root zones. Two days after inoculation, root growth was recorded, and P. aphanidermatum colonization of individual root sections was determined by ELISA. In tomato as well as in bitter gourd the root tip was the root section most sensitive to P. aphanidermatum infection. Application of Si did not affect severe root-growth inhibition by P. aphanidermatum in either species. However, continuous Si supply significantly inhibited the basipetal spread of the pathogen from the infected root apex in bitter gourd but not in tomato. Si application to the roots only during pretreatment or only during/after the infection of the roots failed to inhibit the spread of P. aphanidermatum. Determination and compartmentation of Si in the roots of bitter gourd revealed that apoplastic Si was not, but symplastic Si was, associated with the ability of the plant to reduce the spread of the fungus in roots. It is concluded that accumulation of Si in the root cell walls does not represent a physical barrier to the spread of P. aphanidermatum in bitter gourd and tomato roots. The maintenance of elevated symplastic Si contents is a prerequisite for Si-enhanced resistance against P. aphanidermatum.