The 2009 ASHS Annual Conference

Objective(s):
This workshop will review the current understanding of fruit abscission and how it may be controlled with PGRs in both sub-tropical and temperate crops.

Managing abscission in fruit crops is essential for achieving economic and horticultural objectives.  For crops with chronically poor fruit set, reducing fruit abscission can help improve yields and fruit quality.  Conversely, crops with tendencies toward high rates of fruit set may benefit from increasing early fruit abscission in order to ensure acceptable fruit size and adequate return bloom.  Furthermore, management of abscission near harvest is often desirable to prevent premature fruit drop and to promote an orderly harvest.  Abscission itself is a complex, highly coordinated process that is influenced by environmental, abiotic, and endogenous factors. A general model for understanding this process will be reviewed.  Plant growth regulators have proven to be effective tools in either increasing or decreasing abscission in both temperate and sub-tropical crops. While the field-level effects of PGRs in these systems have been known for some time, recent studies have helped to expand our understanding of the underlying mechanisms that control abscission. The study of alternate bearing crops like avocado and mandarin illustrate the importance of endogenous physiological factors and how they interact with temperature to determine final fruit set. Effects of PGRs and foliar-applied nutrients on these processes will also be presented.  Recent studies in apple with NAA, AVG, and 1-MCP have improved our understanding of which genes control ethylene production, ethylene perception, and cell wall degradation in both the fruit cortex and fruit abscission zones. This information may be useful in developing new strategies for management of preharvest fruit drop.  Workshop presentations will be interspersed with opportunities for discussion and interaction among attendees and speakers with the goal to encourage the exchange of ideas and to spur creative research in this area.