2007 Annual Report
1a.Objectives (from AD-416)
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.
1b.Approach (from AD-416)
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).
A non-destructive system for detection of freeze-damaged oranges. A non-destructive means for determining whether oranges have been frozen without examining the interior of the fruit was developed by the ARS scientists CPQRU, Parlier, CA. Current means of identifying freeze-damaged oranges soon after a freeze event require cutting the fruit and are inaccurate. Oranges exposed to a freeze were found to have small yellow dots on the peel surface when observed under UV light that are distinctive for freeze damage. This offers a means of sorting freeze-damaged from non-damaged fruit to prevent poor quality fruit from entering the marketplace. NP 306; Component 1, Problem Statement 1D.
Identification of the minimum difference in the ratio of sweetness to acidity in navel oranges identifiable by consumers. The smallest change in the ratio of soluble solids (sweetness) to acidity that consumers could identify was determined by the scientists in Parlier, CA. The current maturity standard that determines when navel oranges can be harvested in California is based on the soluble solids to acidity ratio and is believed by the citrus industry to allow poor quality fruit to be marketed. A consumer taste panel compared taste and buying preferences for fruit of known soluble solids/acidity ratios and determined that consumers could detect a difference of two units and prefer to buy the higher ratio fruit. This work provides evidence that raising the current maturity standard by two units could lead to greater sales of early-season navel oranges. NP 306; Component 1, Problem Statement 1D.
Fungicide reduction and enhancement method. Postharvest decay annually causes significant losses of fresh citrus fruit, and control of them by fungicides has been compromised by the development of resistance to them by the fungal decay pathogen Penicillium digitatum. In 2007, fungicide formulation with a dilute solution of potassium sorbate was shown by the scientists in Parlier, CA to improve the activity of these fungicides and to partially control fungicide-resistant strains of the pathogen. The technique allows lower rates of the synthetic fungicides to be used, which reduces grower costs and residues of fungicides in the fruit. Regulatory issues associated with potassium sorbate are few and it is commonly added to many food products. NP 306; Component 1, Problem Statement 1D.
5.Significant Activities that Support Special Target Populations
|Number of patent applications filed||1|
|Number of non-peer reviewed presentations and proceedings||10|
|Number of newspaper articles and other presentations for non-science audiences||9|
Smilanick, J.L., Mlikota, G.G., Fassel, R., Mercier, J. 2006. Influence of temperature, inoculation interval, and dosage on biofumigation with muscodor albus to control postharvest gray mold on grapes. Plant Disease. 90: 1019-1025.
Smilanick, J.L., Mansour, M., Mlikota, G.G., Goowdwine, W.R. 2006. The effectiveness of pyrimethanil to inhibit germination of spores of penicillium digitatum and to control citrus green mold after harvest. Postharvest Biology and Technology. 42:75-85.