Sweet Immunity in Action: Unlocking Stem Reserves to Improve Yield and Quality. A Potential Key Role for Jasmonic Acid.

Common agronomic practices such as stem topping, side branch removal, and girdling can induce wound priming, mediated by jasmonic acid (JA). Low light conditions during greenhouse tomato production make the leaves more sensitive to the application of exogenous sugar, which is perceived as a "danger" in accordance with the concept of "Sweet Immunity". Consequently, source-sink balances are altered, leading to the remobilization of stem starch reserves and enabling the redirection of more carbon toward developing fruits, thereby increasing tomato yield and fruit quality. Similarities are drawn with the mobilization of fructans following defoliation of fodder grasses (wounding) and the remobilization of fructan and starch reserves under terminal drought and heat stress in wheat and rice (microwounding, cellular leakage). A central role for JA signaling is evident in all of these processes, closely intertwining with sugar signaling pathways. Therefore, JA signaling, associated with wounding and sugar priming events, offers numerous opportunities to alter source-sink balances across a broader spectrum of agricultural and horticultural crops, for instance, through the exogenous application of JA and fructans or a combination. This may entail reconfiguring and reversing phloem connections, potentially leading to an enhanced yield and product quality. Such processes may also disengage the growth-defense trade-off in plants.