BACKGROUND: Eliciting host plant resistance using plant hormones such as jasmonates has the potential to protect seeds and seedlings against insect pests; however, several hurdles exist for adapting it for pest management. This includes determining a dose that promotes resistance without limiting plant growth, an application method that growers could use, and ensuring the plants are responsive in the abiotic conditions when the pest occurs. In laboratory and field assays, we tested if treating corn seeds with multiple concentrations of methyl jasmonate would reduce the preference of ovipositing seed corn maggot adults and the performance of larvae feeding on seeds. RESULTS: We found that corn seeds soaked in aqueous 0.2 mM methyl jasmonate solution showed marginally lower seedling growth, but the adult oviposition preference was similar to 60% lower on these seeds compared to control water-soaked seeds. Seeds that were treated with methyl jasmonate using a conventional polymer-based seed coating showed no effect on seedling growth but reduced adult oviposition preference. In no-choice bioassays with adult flies, we found reduced oviposition on seeds soaked with aqueous methyl jasmonate compared to controls. Larval survival to pupation was also lower in methyl jasmonate-treated seeds. Lastly, the methyl jasmonate-induced resistance also occurred at the lower temperatures typical of the spring soil conditions when this fly is most damaging. CONCLUSION: Methyl jasmonate seed treatment in aqueous solution or using conventional polymer-based technology, has the potential to deter adult oviposition and reduce maggot performance in spring temperature conditions with minor effects on seed germination and growth. (c) 2024 Society of Chemical Industry.

Methyl jasmonate (MeJA) is a phytohormone involved in plant defense against stress. However, its application as pretreatment in soybean seeds is limited. Here, we investigated whether seed pretreatment with MeJA mitigated the negative effects of water restriction (WR) and mechanical wounding (MW) in soybean seedlings at the V1 vegetative stage. Seeds of Glycine max (Monsoy 6410 variety) were pretreated with water or 12.5 mu M MeJA for 14 h. The obtained seedlings were transferred to pots containing substrate (soil and sand) kept in a greenhouse and subjected to different growth conditions: control (no stress), WR (40% water retention), and MW. The experiment was conducted in a 2 x 3 factorial scheme (2 seed pretreatments x 3 growth conditions). The variables analyzed were ethylene levels, hydrogen peroxide, lipid peroxidation, antioxidant system enzymes, sugars, amino acids, proteins, proline, and growth (root and shoot length). WR negatively affected seedling growth, regardless of seed pretreatment, but proline levels increased with MeJA application. In seedlings subjected to MW, MeJA increased ethylene release, which was related to reduced damage. It suggests that pretreatment of soybean seeds with MeJA is a promising tool to mitigate the deleterious effects of biotic and abiotic stresses during seedling establishment, inducing distinct tolerance strategies.