Influence of chitosan on the antioxidant status of tomato plants infected by cucumber mosaic virus

Fruit quantity and quality loss represents a huge problem for farmers and more generally for human nutritional needs. Viruses are dangerous phytopathogens, that cannot be faced using agrochemicals. Hence, they are responsible for severe crop and quality losses. In such a scenario, chitosan is an interesting eco-friendly solution. The strong decrease of the load of cucumber mosaic virus strain Fny (CMV-Fny) in Solanum lycopersicum plants, treated with the combination of Trichoderma harzianum T-22 and chitosan, has been previously reported. The present research was aimed to investigate the influence of chitosan on the antioxidant status of CMV-inoculated tomato plants. The transcript amounts of the genes encoding peroxidase, phenylalanine ammonia lyase (PAL) and phytoene synthase 2 (PSY2), were analyzed in leaves. Lutein, lycopene, β-carotene, vitamin C and polyphenols as rutin and naringenin, were determinated in ripe fruits. Results show that chitosan treatment, both before CMV and alone, downregulated peroxidase- and PSY2-related transcripts, while upregulated PAL-related transcripts, compared to only infected plants. Fruits harvested from plants treated with chitosan alone had the highest lutein, lycopene and β-carotene contents. The same fruits also contained more caffeoyl glucoside and less naringenin chalcone, compared to the fruits of control plants. Furthermore, the fruits of control plants had the lowest vitamin C level. In conclusion, chitosan was able to enrich fruits with nutraceuticals, as carotenoids, and it controlled CMV infection likely through phenylalanine-derived products, such as salicylic acid, by affecting the plant antioxidant status.