Preharvest and Postharvest Practices to Extend the Shelf-life of Table Grapes
Commodity Protection and Quality
Project Number: 5302-43000-036-11
Start Date: May 01, 2013
End Date: Apr 30, 2014
To develop preharvest and postharvest practices to extend the shelf-life of table grapes. Specific objectives include: 1) assemble a large collection of Botrytis cinerea isolates from numerous vineyards in the San Joaquin Valley and determine their sensitivity to fungicides; 2) determine the effectiveness of fungicides applied at various times in vineyards before harvest on the incidence of summer bunch rot and subsequent decay after harvest; 3) determine residue levels and their persistence at harvest and during cold storage, and the influence of sulfur dioxide or ozone gas on their persistence; 4) evaluate the effectiveness of periodic or cyclic low concentration ozone use during cold storage (as opposed to constant low ozone concentration), with or without weekly sulfur dioxide fumigation, to control postharvest decay.
Isolates of Botrytis cinerea will be collected from table grape vineyards at various locations in the Central Valley of California. PCR will be performed using selected molecular makers to separate isolates into either genetic Group I or Group II. Selected isolates will be tested on agar media for sensitivity or resistance to selected fungicides. Fungicides applied at different timings before harvest in a commercial vineyard will be evaluated for control of summer bunch rot in the field and postharvest decay in berries during cold storage. Berry residue content and residue persistence of the selected fungicides will be determined. In addition to storage in air, the influence of ozone and sulfur dioxide fumigation on fungicide residues will also be determined.