The effects of brassinosteroids (BRs) against blue mould rot caused by Penicillium expansum and on senescence of harvested jujube fruit were investigated. Brassinosteroids at a concentration of 5 mu M effectively inhibited development of blue mould rot and enhanced the activities of defense-related enzymes, such as phenylalanine ammonia-lyase, polyphenoloxidase, catalase and superoxide dismutase. However, BRs did not have direct antimicrobial activity against P. expansum in vitro. BRs significantly delayed fruit senescence by reducing ethylene production and maintained fruit quality. It is suggested that the effects of BRs on reducing decay caused by P. expansum may be associated with induction of disease resistance in fruit and delay of senescence. (C) 2009 Elsevier B.V. All rights reserved.