PEPTIDE EXTRACTS OF FULLY-EXPANDED LEAVES FROM EGGPLANT IN THE INHIBITION OF Ralstonia solanacearum AND Clavibacter michiganensis subsp. michiganensis GROWTH AND ACTIVITY AGAINST JUVENILES OF Meloidogyne javanica
Mattos, E. C.1,2; Almeida, H. O.1,2; Barbosa, M. O.1,2; Koscky-Paier, C. R.1,2; Magalhães, R. D. M.1,2; Romeiro, R. S. 3; Podestá, G. S. 3.; Freitas, Leandro Grassi 3; Fontes, E.P.B. 1,2; Baracat-Pereira, M.C 1,2.
1Departamento de Bioquímica e Biologia Molecular, 2Laboratório de Proteômica, BIOAGRO, UFV, 3Departamento de Fitopatologia/UFV 36570-000 Viçosa, MG
Some eggplant (Solanum melongena L.) varieties are little susceptible to certain plant-pathogen, probably because plants are capable of synthesizing, in an economical and efficient way, natural defense compound, and antimicrobial peptides (AMPs) could be involved. The major aim of this work was to test the inhibitory activity of peptide-eggplant extracts against the bacteria Ralstonia solanacearum and Clavibacter michiganensis subsp. michiganensis growth, and in death or immobility of juveniles of plant-parasitic nematodes Meloidogyne javanica. Fully-expanded leaves were powdered (liquid N2) and macerated (Tris-HCl 50 mM pH 7,5, EDTA, benzamidine, thiourea and PMSF). The extract was centrifuged and the supernatant corresponded to the Raw Soluble Extract (RSE). The precipitate was washed (water, 3x) and extracted with LiCl 1,5 M (EDTA, benzamidine, thiourea and PMSF). The homogenate was centrifuged and the recovered supernatant consisted of the Raw Cell-Wall Extract (RCWE). RSE and RCWE were separately fractionated with ammonium sulfate (35% sat.) and heating (80oC/15 min), dialyzed (cut-off 1000 Da membranes), and recovered fractions were named SE and CWE, respectively. Both SE and CWE were submitted to inhibition tests against the two mentioned bacteria and to inhibition tests (death or immobility) against juveniles of the nematode. For antimicrobial tests, four different SE and CWE concentrations were used (corresponding to 0.5 g, 0.75 g, 1.0 g and 1.25 g of dry leaves). After 14 h growth time, inhibition rates of R. solanacearum were superior to 90% and 80% for SE and CWE, respectively. For C. michiganensis subsp. michiganensis, the inhibition rates for SE and CWE were superior to 80% and 65%, respectively. For the tests against the nematode, concentrations of SE and CWE corresponded to 0.5 g, 1.0 g, 1.5 g and 2.0 g of dry leaves. Mobile and immobile nematode number were evaluated after 24 h and 48 h in contact with the extracts, and after 72 h, when water replaced the extracts at 48 h. The largest effects were detected for the more concentrated extracts (2,0 g), when it was observed 25.8, 56.6 and 16.3% of immobile nematodes for SE, in 24, 48 and 72 h, respectively, and 42.8, 44.4 and 26.8% of immobile nematodes for CWE, in 24, 48 and 72 h, respectively. The smallest values observed for 72 h indicate a nematostatic effect of these extracts. New tests with more concentrated extracts are being developed against these nematodes.
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