برسی اثر کیتوزان بر روی گوجه‌فرنگی آلوده به نماتد Meloidogyne javanica در شرایط گلخانه

Chitosan is a non-toxic, biodegradable natural biopolymer commercially produced from chitin found in the exoskeletons of crabs and shrimps. Chitosan is made in various molecular weights, each with unique properties that influence its effectiveness in enhancing plant growth. High molecular weight chitosan (over 700 kDa) is helpful for the strengthening of the plant roots, while medium (150-700 kDa) and low molecular weight chitosan (less than 150 kDa) increase photosynthetic pigments and induce resistance against biotic stresses in plants. Recent studies have shown the influential role of chitosan in the management of root-knot nematodes (Meloidogyne spp.) as the most dangerous plant-parasitic nematodes. This study evaluated the application of high, medium, and low molecular weight chitosan on tomato plants infected with M. javanica under greenhouse conditions. Organic materials, including chitin, can change the physicochemical properties of the soil, release nematicide compounds such as organic acids and nitrogen compounds (NH3), and can induce plant resistance by increasing antagonist microorganisms, resulting in the suppression of nematode populations. For this purpose, tomato seeds cv. Early-Urbana were sown in plastic pots containing one kilogram of growing medium (equal amount of farm soil, sand, and decomposed cow manure) and maintained in a greenhouse (27±4°C temperature, under 16:8 h (light: dark) photoperiod). Four-leaf stage seedlings were separated into two groups and, each group into two subgroups. Seedlings inoculated with 4000 eggs of nematode and simultaneously (in the first group) and seven days after nematode inoculation (in the second group), soil drenched with 20 mL of 1% (in the first subgroup), and 2% (in the second subgroup) chitosan with high, medium, and low molecular weight. The experiment was performed in a factorial arrangement in a completely randomized design with four replications. After 60 days, plants were harvested and plant growth indices and nematode population indices were assessed. Results showed that all growth indices of nematode-infected plants treated with chitosan significantly increased compared to inoculated control (non-treated) plants. Additionally, the nematode reproduction factor in the first and second subgroups of the first group which treated with high, medium, and low molecular weight chitosan decreased by 19.8%, 24.8%, 22.8%, and 28.5%, 28.1%, 23.6%, respectively, and in the second group decreased by 16.5%, 19%, 26.7%, and 25.5%, 24.4%, 28.1%, respectively, compared to non-treated plants. This research showed that soil drenching with chitosan simultaneously with nematode inoculation enhanced the vegetative indices of tomato plants and reduced the infection of M. javanica.