Testing chitosan-based Fosetyl-Al nanocrystals in Meloidogyne javanica control

Plant-parasitic nematodes, which are ubiquitous and have high reproductive rates, are undoubtedly a serious threat to food security and plant health, causing an annual loss of approximately USD 100 billion worldwide. Root-knot nematodes Meloidogyne spp. are responsible for extensive yield loss of horticultural and field crops. The difficult management of plant parasitic nematodes often relies on chemicals. However, due to their negative impact on human health and the environment, many major nematicides have been withdrawn or banned in recent decades. The need for control measures with less environmental impact has led to the renewed search for alternative strategies, such as nanotechnology. The aim of this study is to investigate the potential efficacy of a new formulation of Fosetyl-Al, a well-known systemic fungicide also used as bactericide, in the control of Meloidogyne javanica. In-vitro experiments were performed using chitosan-based Fosetyl-Al nanocrystals (CHnanoFos), prepared by a sonication-assisted method, applying chitosan as a coating agent. In order to determine the optimal concentrations of CH-nanoFos to be tested against M. javanica, a series of preliminary experiments were carried out. The potential nematicidal, nematostatic and hatching inhibition activities of three different concentrations of CH-nanoFos (1 mg/ml, 2 mg/ml and 4 mg/ml) at different exposure times were then compared. Nematostatic and nematicidal activities were evaluated on second-stage juveniles after 24 and 48 hours of exposure to CH-nanoFos. There was a statistically significant interaction between the effects of the tested nanoproduct concentration and exposure time for both parameters evaluated. In general, the nematicidal effect increased as the tested concentration and exposure time increased. In contrast, the nematostatic effect decreased with increasing tested concentration and exposure time. To investigate the potential hatching inhibitory activity, M. javanica eggs were incubated with CH-nanoFos and the number of juveniles was estimated after 3, 7 and 14 days. There was a statistically significant interaction between the effects of the tested nanoproduct concentration and incubation time, in fact, the inhibitory activity of CH-nanoFos on M. javanica egg hatching increased with increasing concentration and incubation time. Regarding future perspectives, the efficacy of CH-nanoFos in controlling this root-knot nematode will also be evaluated in vivo through pot experiments. Its potential phytotoxicity is currently under investigation on tomato plants