Extratos aquosos de diferentes culturas e herbicida glifosato sobre a eclosão, desenvolvimento embrionário e controle de Meloidogyne javanica em soja

Abstract

The nematodes of the genus Meloidogyne are responsible for significant losses in agricultural production, including in the soybean crop. To mitigate these losses, the search for control measures has been stimulated, such as the use of plant extracts with potential to induce resistance in plants. Weeds are also a limiting factor for productivity, and the application of herbicides to their control can affect the nematode population. Two trials were performed, one in the laboratory (in vitro) and the other in a greenhouse (in vivo). In vitro the aim of this study was to evaluate the effect of leaf and root extracts of Brassica napus L. (Canola), Crotalaria juncea L. (Crotalaria), Brachiaria decumbes L. (Brachiaria), Helianthus annus L. (Sunflower), Triticum aestivum L. (wheat) and Lupinus albus L. (lupine), associated or not with glyphosate application, on a suspension containing eggs and juveniles (J2) from Meloidogyne javanica, using water as a control. The second objective was to evaluate the effect of spraying of leaf and root extracts of the same species mentioned above, associated or not with the application of glyphosate, in soybean inoculated with M. javanica. The assays were conducted under a completely randomized design (DIC) with four replicates, in a 7 x 2 factorial scheme, with six aqueous extracts and the control, with and without glyphosate, which were divided into two parts, experiment I: aqueous extracts from the aerial part of the mentioned plant species and experiment II: extracts of the root part of the same. For the in vitro assay, in Petri dishes were placed with 9 mL of the extracts and one suspension with 900 eggs/J2 of M. javanica, for the treatments with herbicide, was added 0.72 mL i.a. of glyphosate. After 15 days hatching and embryonic development were evaluated. The application of glyphosate influenced the analyzed variables, inhibiting in 100% hatching and retarding the embryonic development. Among the evaluated extracts, wheat extract (Triticum aestivum L.) inhibited hatching by 100%. For the in vivo assay, soybean plants were induced to spray resistance in the 20 mL aerial (part of the extracts and for the herbicide treatments 0.72 mL of glyphosate was added to the plants), after seven days a suspension of 1,400 eggs of M. javanica per plant. At 60 days, height, fresh root mass, number of pods, egg mass, gall, eggs e J2 and M. javanica breeding factor (RF) were evaluated. The presence of glyphosate mainly influenced height decreasing by 20% for treatments with leaf extracts and 25% for root extracts. In the experiment with leaf extracts the extract of crotalaria (Crotalaria juncea L.) reduced the number of eggs/J2 (63%) in relation to the control. All evaluated root extracts, with and without glyphosate, reduced the number of eggs/J2 in relation to the control by 80% between 89%, respectively. The RF of all the treatments were also smaller in comparison to the control, but, only the canola extract (Brassica napus L.) (0.98) had the FR lower than 1.0, thus demonstrating some potential as inducer of resistance against M. javanica in soybean.