520 Methyl Jasmonate Causes Ethylene Production and Abscission in Citrus

Abstract

Methyl jasmonate (Me-Ja) is a naturally occurring ubiquitous compound in plants. Me-Ja is considered to be a putative plant hormone because of its effect on plant processes such as senescence, germination, tuber formation, signal transduction, ethylene production, and abscission at low exogenous concentrations. We applied Me-Ja to fruit or whole trees of `Hamlin' or `Valencia' orange to determine the potential of this compound as a mature fruit abscission agent. Me-Ja (0, 1, 5, 10, or 20 mM in 0.1% Kinetic adjuvant) was applied to whole trees with a handgun or boom sprayer rates of 4850 and 1790 L·ha–1, respectively. Alternatively, tree fruit were dipped in Me-Ja solutions. Fruit drop, leaf drop and ethylene production in both fruit and leaves and fruit detachment force in fruit were monitored at various times up to 2 weeks after application. Me-Ja treatment resulted in increased ethylene production in fruit and leaves 1 to 2 days after application. Fruit detachment force significantly declined 6 to 10 days after application followed by significant fruit drop. Applications of Me-Ja >10 mM resulted in an unacceptable amount of canopy defoliation. The results suggest that Me-Ja has potential as an abscission agent for citrus. Future work will focus on improving uniformity of application and response.