Chamada à distância: auimiotaxia de Meloidogyne javanica a compostos orgânicos voláteis emitidos por raiz de soja

Abstract

The root-knot nematode, Meloidogyne javanica, is a harmful pathogen for soybeans. Understanding how the semiochemicals released by the soybean root system affect the second juvenile (J2) of M. javanica can help in the development of new management measures for this pathogen. In the present study, an open environment technique was developed for the study of J2 chemotaxis in soil. Our results indicate that the roots of soybean cv. Monsoy 5917 IPRO release semiochemicals that are attractive (p < 0.05) to juveniles. However, most J2 remained close to the infestation site, apparently without being affected by the semiochemicals. Next, by means of gas chromatography coupled to mass spectrometry (GC-MS), the volatile organic compounds (VOCs) released by the soybean root system were identified. A total of 13 compounds were detected in soybean emissions, of wich six: ethyl acetate, ethyl benzoate, etanol, tetradecane, 2-pentylfuran and 3-pentanone, were acquired and tested in vitro chemotaxis assays. In addition to these VOCs, the compounds vanillin and salicylic acid were also tested and these were not identified in the GC-MS of soybeans and were used for comparison routes beacuse they appear in the literature as attractive to the J2 of Meloidogyne sp. The J2s were not attracted to any of the six VOCs detected in soybean root, but were highly attracted to the compounds vanillin and salicylic acid. Finally, using the chemotaxis technique developed here, the compounds vanillin and salicylic acid were tested in pots containing a mixture of sand and soil. In the first test, in the region of application of the salicylic acid compound, an average of 6x more J2 was recovered. However, in the second assay none of the compounds attracted J2.