Effect of Citrus sinensis pomace extract and its fractions on the interaction between Meloidogyne javanica and soybean

Numerous extracts derived from agroindustrial wastes, such as Citrus sinensis pomace, have been found to contain bioactive compounds with nematicidal activity. This study aimed to evaluate the effect of the ethyl acetate (EAF) and dichloromethane (DCMF) fractions of a methanolic extract from Citrus sinensis pomace on the penetration and reproductive capacity of Meloidogyne javanica on soybean, as well as on plant defense responses. The reproduction test comprised the following treatments: untreated control, EAF, DCMF, EAF + DCMF, abamectin, and Allium sativum extract. Extract solutions were diluted to 1.5% before application. The penetration experiment comprised an untreated control, EAF, DCMF, and EAF + DCMF. Nematode penetration and expression of defense enzymes were evaluated at 5, 15, and 25 days after inoculation (DAI). All treatments reduced nematode reproduction compared with the control, with abamectin providing the highest reduction (78%), followed by DCMF (51%), EAF + DCMF (50%), EAF (44%), and A. sativum extract (44%). All extract fractions reduced nematode penetration and total number in soybean roots compared with the control. Additionally, extract fractions exerted significant effects on plant defense responses. EAF promoted POX activity at 2 and 4 DAI, as well as CAT activity at 2 and 8 DAI. DCMF increased PAL activity at 10 and 12 DAI. EAF and DCMF promoted an increase in PPO activity, but values did not differ from the control. Finally, EAF + DCMF enhanced CAT activity at 8, 10, and 12 DAI. Both fractions of the methanolic extract from C. sinensis pomace show promise in controlling M. javanica and eliciting defense responses in soybean.