Immune response of root-knot nematode-infected tomato is improved by biogenic copper nanoparticles.

"Green" synthesized copper nanoparticles from hemp plant waste (Cu-G-NPs) identified as brochantite, together with chemically synthesized copper nanoparticles (Cu-C-NPs), and copper sulfate (CuSO4) were tested as foliar spray against Meloidogyne incognita in tomato (Solanum lycopersicum).The materials were evaluated in two separate greenhouse experiments designed to assess their effectiveness at the different temperatures: one under warmer growth conditions and another stimulating cold stress. In both experiments treatments were applied at 200 mg/L of Cu and effects were assessed over a 45-day-period. Cu-G-NPs decreased nematode egg numbers by 41 % (significantly more than CuSO4 (35 %) and Cu-C-NPs (20 %)) and the number of galls by 38 % (significantly more than Cu-C-NP (24 %) and comparable to CuSO4 (43 %)). In treatments with Cu-G-NPs, plants had a lower content of malondialdehyde (41 % decrease, compared to 25 % and 28 % decreases with Cu-C-NPs and CuSO4, respectively) compared to infected control plants. Addition of Cu-G-NPs modulated hormonal response in the plants, by upregulating ethylene biosynthesis in leaves and downregulating salicylic acid-mediated response in roots. The presence of bioactive compounds, such as amines, carboxylic acids, esters, and sterols, on the surface of Cu-G-NPs (as determined using attenuated total reflectance Fourier-transform infrared spectroscopy) increased their effectiveness when compared to Cu-C-NPs and CuSO4.