Compostos orgânicos voláteis de sementes de mamão tóxicos a Meloidogyne incognita

Abstract

Volitelie organic compounds (VOCs) emitted from many plant species are toxic to plant-parasitic nematodes. Thus, this work aimed to verify the activity of papaya (Carica papaya)seeds VOCs against Meloidogyne incognitasecond stage juveniles (J2) by Supelco tubes technique. The J2 were exposed to VOCs for diferent exposure time (1.5, 3, 6, 12, 24, 48 h). After 48 h of exposure the J2 mortality reach 100%. The rest of J2 were applied around tomato roots to evaluate the infectivity and reproduction of exposed J2. From 6 h exposure the infectivity decreased 80% and eggs decreased more than 90%. Both infectivity and reproduction were completely reduced after 48 h exposure. We also verified the effect of papaya seed incorporated into artificial substrate by biofumigation at greenhouse. Over the incorporated substrate a microtube were half buried where J2 were incubated inside. Different amounts of papaya seed were incorporated: 0, 1, 2, 4 e 8 g along with M. incognita eggs. After 40 days of planting tomato seedlings the infectivity and reproduction were estimated from the roots and the mortality was verified from J2 inside the microtubes. From 4 g of papaya seed incorporation the infectivity decreased by 90% while the reproduction decreased more than 90%. By applying 100 % reduction on infectivity and reproduction were reached. When the water was exposed to VOCs of papaya seeds no activity was verified against M.incognita J2. Furthermore, 17 compounds were identified from papaya seeds volatilome by gas chromatography (GC/MS). From the volatilome the compounds vinyl acetate, phenylacetaldehide and benzoylacetonitrile were selected to follow in vitro analyses against M. incognita. Acetato de vinila, fenilacetaldeído and benzilacetonitrila killed the M. incognitaJ2 with lethal concentrations of (LC50) of 61 µg / mL, 103 µg / mL e 15 µg / mL respectivly.