Compostos orgânicos voláteis emitidos pelas raízes de tomateiro na atração e repelência de Meloidogyne javanica: nova técnica em vaso

Abstract

Meloidogyne javanica is a pathogen of great economic importance, causing damage to large-scale crops such as tomato. This phytoparasite has sensory organs that allow the recognition of semiochemicals present in the soil solution and their direction to the roots of the plants. In the present work we developed a technique to study the chemotaxis of second-stage juveniles (J2) of M. javanica to semiochemicals. For the first time, a technique was used that makes it possible to separate the regions of the pot substrate from the tomato rhizosphere into attractive 1 and 2, neutral and repellent regions, using screens that allowed free movement of M. javanica J2. With the aid of the new technique, it was found that the tomato rhizosphere in the attractive region 1 changes the distribution profile of M. javanica J2 compared to the control treatment, without the plant. The tomato rhizosphere caused a positive chemotaxis, attracting most of the J2 to the attractive region 1, in contrast to the control, where it had a lower incidence. Twenty-four volatile organic compounds (VOCs) were found in the emissions of tomato roots in the analysis performed in a gas chromatograph, coupled to a GC-MSQP20 Ultra mass spectrometer (Shimadzu, Japan) equipped with an automatic injector for liquid and gases. For the first time it was found that the volatiloma component of tomato roots ethylhexanol causes high attraction and that the VOCs hexanol and 1-menthol also attract J2 from M. javanica. Using the new technique, it was found for the first time that the amounts of 1mL and 3mL of ethylhexanol significantly attracted J2. The new technique has great precision in the quantitative evaluations of nematodes in attractive and repellent processes by working with the entire substrate. It also has a low cost and saves time, since it can be carried out in a greenhouse with a duration of only five days of development, in addition to presenting an excellent approximation with the reality of research carried out in the field.