Citrus fruit abscission induced by methyl-jasmonate

Methyl jasmonate (MJ) mas tested as a potential abscission chemical to enha nce mechanical harvest of 'Hamlin' and 'Valenica' orange [Citrus sinensis ( L,) Osb.]. In field experiments, a solution of 1, 5, 10, 20, or 100 mM MJ w as applied either as a stem wrap to individual fruit or as a spray to entir e trees or canopy sectors. Solutions of 10, 20, and 100 mM MJ resulted in s ignificant and consistent reduction of fruit detachment force and caused fr uit drop within 7 to 10 days. Fruit loosening was preceded by an increase i n the internal ethylene concentration of fruit similar to that of other exp erimental abscission compounds. While concentrations of 10 mM and less caus ed no or negligible phytotoxicity, solutions exceeding 10 mM MJ induced una cceptable levels of leaf abscission.