TABLE CONTENTS

Secondary Metabolites Present in Canavalia ensiformes Seeds are Toxic to
Juvenile Plant Parasitic
Rocha, T.L. (1), R.G.S. Evaristo (1,3), O.L. Franco (4), R.M.D.G. Carneiro, L.A. Fothergill-
Gilmore, E.R. Silveira, D.S.L. Souza (1,2), L.P. Silva (1), B.S. Magalhães (1),M.C.M. Silva
(1) & M.F. Grossi de Sá (1,4)
(1) Embrapa Recursos Genéticos e Biotecnologia, Brasília, Brazil; (2) Universidade de Brasília, Brasília-DF,
Brazil; (3) Faculdades Integradas da Terra de Brasília, Brasília-DF, Brazil; (4) Centro de Análises Proteômicas e
Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de
Brasília, Brasília, Brazil.
Plant parasitic nematodes of the genera Meloidogyne sp. cause remarkable losses to important
world-wide crops reaching up to 120 billion dollars annually. Currently, their control is based
on synthetic nematicides that, beyond expensive, cause risks to the human health and
environment. Consequently, search for new and safer strategies for managing these pathogens
are urgently required. Plants are source of natural products, which may possess nematicidal
compounds. In this context, a screening for specific and effective molecules towards second
stage juvenile (J2) of Meloidogyne incognita was carried out using aqueous seed extracts of
Canavalia ensiformis, Crotalaria juncea, Crotalaria paulinea, Crotalaria espectabilis,
Tagettes minuta, and Mucuna pruriens. Amongst all the tested extracts, those from C.
ensiformis showed the highest nematicidal activity (85%). Dialysis fractionation of the crude
components from C. ensiformis allowed us to separate molecules smaller than 3.5 kDa
(External dialysis) which are very effective against J2 nematodes but innocuous to
phytopatogenic fungi, saprophytic nematode, protozoan, larvae of Spodoptera frugiperda and
Antonomus grandis. Mass spectrometry revealed the existence of wide variety of secondary
metabolites in this fraction. Hemolysis tests showed that these components were not able to
disrupt bovine red blood cells. When submitted to 50°C for 24 hours nematicidal activity
reduced only 20% illustrating their thermostability. Green house bioassays carried out on
tomato roots employing the dialysis fraction reduced the number of egg masses with 82.5%
corroborating our results on nematicidal activity. Metabolites were further purified by HPLC
resulting in a more pure and very effective fraction causing 98% mortality of J2 nematodes.
Microscopic analysis revealed that this fraction induces the complete disruption of the J 2
intestine due to an abundant vacuolization of epithelial cells. Mass spectrometry and NMR
analysis are currently being performed in order to elucidate the molecular structure of these
compounds.
Supported by EMBRAPA, CNPQ, CAPES, FAP-DF
5 th International Congress of Nematology, 2008 315