Piper Extracts in Alternative Control of phytonematoids of the genus Meloidogyne in Coffea canephora

Abstract

Gall nematodes are known worldwide for causing severe damage to agriculture. In Brazil, species of the genus Meloidogyne are responsible for losses in the production of several crops distributed throughout the country. Given the difficulty in controlling these nematodes, several strategies have been studied, and among them, the use of plant extracts represents a low cost alternative and less aggressive to the environment. Thus, the objective of this work was to evaluate the effect of aqueous extracts of different Piper species on the control of M. incognita in in vitro and in vivo assays on Coffea canephora seedlings. The studies were conducted in the phytopathology laboratory and in the greenhouse of Embrapa Rondônia, in Porto Velho. Six species of the Piper genus were used for the evaluations, obtaining the aqueous extracts of leaves, stems and inflorescences, used fresh and dry, at a concentration of 0.1µg / mL. The experimental design was completely randomized, with 58 treatments and six replications, in addition to controls with sterile mineral water and nematicide (Carbofuran, 20mL.L-1). For in vitro tests, Elisa type acrylic plates were used as support for the microtubes, where they were placed separately in each well of the Eppendorfs 100 (µL) extracts and 100 (µL) of the suspension containing 50 eggs of the respective nematode. Eggs were extracted using the methodology described by Hussey et al. (1973), modified by Boneti and Ferraz (1981). The plates were taken to B.O.D incubators at 25 ° C for 15 days in the dark. On the sixteenth day we evaluated the number of eggs, hatched juveniles (J2), immobile and mobile. Of all Piper extracts tested, seventeen were able to significantly inhibit phytonematoid outbreaks. Of these, we highlight P. hispidum and P. tuberculatum, which presented the best inhibitory effects (ovicidal + larvicidal action). From then on, choosing the extracts that showed effect in the in vitro assays, we conducted the in vivo experiment in a greenhouse. Six-month-old C. canephora (Clone CPAF-RO C750 susceptible) seedlings, kept in 8L pots, were inoculated with 5000 M. incognita eggs. After 24 hours 720mL of extracts were applied per pot. The application of the extracts was repeated at 30, 60 and 90 days after inoculation, being evaluated after 150 days for the reproduction factor (FR), the number of galls per gram of roots (NGGR) and the number of eggs per gram of roots (NOGR). The experimental design in vitro and in vivo was completely randomized with six replications. Data were submitted to ANOVA and the means compared in Scott-Knott test at 1% and 5% respectively. Among the extracts tested in vivo, sixteen showed significant reduction in relation to RF, NGGR and NOGR, when compared to the control, highlighting the species P. carniconnectivum, P. permucronatum, P. tuberculatum and P. umbellatum, as they demonstrated efficiency in population control of gall nematode by reducing RF when compared to control with commercial nematicide. It is concluded that the aqueous extracts of Piperaceae have nematicidal activity and can be used in the development of future methods of chemical and cultural control, in partial or total replacement to conventional nematicides.