Project Number: 5302-43000-032-00
Project Type: Appropriated

Start Date: Sep 02, 2004
End Date: Sep 01, 2009

Objective:
This project includes multidisciplinary work on maintaining the quality of California-grown fresh commodities. Research will be conducted on the effects of postharvest treatments on injury and decay, the relation between fruit phenology and susceptibility to decay, and the effects of postharvest treatments on the composition of fresh commodities. This research seeks to: 1) Minimize postharvest decay losses of citrus and grapes using microbial biological control, generally-recognized-as-safe (GRAS) or reduced-risk compounds, and thermal treatments. 2) Identify and quantify morphological features (e.g. pericarp thickness, porosity, cell density) and constitutive or inducible biochemical constituents (e.g. phytoalexins, PR proteins, phenolic compounds) in grape selections that could mediate resistance to Uncinula necator and Botrytis cinerea. 3) Determine the relationship of antioxidants with peel quality in lemons and fruit volatile content, brix and acidity on consumer acceptance of navel oranges as influenced by maturity and postharvest handling.

Approach:
Evaluate the effectiveness of microbial biological control antagonists, substances classified as GRAS, certified organic, or reduced-risk compounds and thermal treatments in controlling significant postharvest pathogens of citrus fruit and grapes using laboratory assays. Promising treatments will then be included in large scale semi-commercial tests with cooperators to optimize their efficacy and assess their commercial feasibility. Assess resistance to gray mold (Botrytis cinerea) and powdery mildew (Uncinula necator) among grape selections using laboratory and field evaluations. Constitutive or inducible biochemical constituents and morphological features from these selections will be quantified to determine their contribution to disease resistance. Subject lemons to various durations and degrees of heat treatments and assay areas of the peel that show incipient injury for antioxidant status as well as for signs of oxidative injury. Measure fruit volatiles and quality factors such as brix and acidity and relate to the palatability of the fruit as influenced by time of harvest and various postharvest handling treatments. Formerly 5302-43000-029-00D (8/04).