• Evaluation of a New Harpin Product on Microbial Quality and Shelf Life of Minimally Processed Lettuce

      Fonseca, Jorge; Kline, Wesley L.; Wyenandt, Christian A.; Hoque, Mushidul; Ajwa, Husein; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center; Rutgers Cooperative Extension - Bridgeton, NJ; University of California, Davis /USDA-ARS, Salinas CA (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      The effect of pre-harvest application of Extend®, a newly developed second generation harpin product, on shelf life of fresh-cut lettuce was investigated. The lettuces were grown in locations A: Watsonville, CA; B: Cedarville, NJ; and C: Yuma, AZ, and treated five days before harvest at 30, 60 and 90 ppm (2,4 and 6 oz/acre in 50 gal/acre). Lettuce processed and bagged was stored at 34-37°F and evaluated for quality for 20 days. Lettuce from trial A treated with 60-90 ppm harpin consistently had a better overall quality and lower microbial population than the control. Results from trial B showed no differences among treatments. In trial C, microbial population was lower and visual quality higher in lettuce treated at 60 ppm than the control during early stages of storage. Overall results are mixed but it was revealed that a field application of harpin can improve quality of fresh-cut lettuce under conditions that need to be determined.
    • Evaluation of the Effect of Cytokinin Products on Yield of Head Lettuce

      Fonseca, Jorge; Byrne, David N.; Baciewicz, Patti; The University of Arizona – Yuma Agricultural Center, Yuma AZ (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      A series of replicated trials were conducted during the winter season of 2003 and 2004 to investigate the effect of pre-harvest applications of cytokinins on yield and postharvest quality of intact and fresh-cut lettuce. We report here only those results obtained at harvest. Cytokinins products were applied at different frequency and rates. The crops in the different trials were under different cultivation programs, including different nitrogen fertilization rates. Figures showing the performance of each individual cytokinin product versus the corresponding untreated controls are provided. Results obtained are mixed even for the same cytokinin product, however, some trends were observed. With the exception of products that also contain other plant growth regulators in their formula, high rates (or multiple applications) of the cytokinin products resulted in no effect or even in negative results. For example applications of Cytokin® did not improve yields as was the case with Cytoplex®, from the same manufacturer, under different conditions. The results from this study suggest that lettuce plants can respond to cytokinin applications, but factors to enhance positive response still need to be studied further. Single applications appear to be the most effective program for products containing only cytokinins, while products such as Cytoplex® can increase yield with multiple applications. A discussion addressing the different results obtained with nitrogen rates and the cytokinin products in yield and quality is included.
    • Microbial Quality of Iceberg Lettuce is Affected by Moisture at Harvest - 2nd Year Evaluation

      Fonseca, Jorge; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      In a continuing work, the effect of moisture conditions on yield and microbial quality of Iceberg lettuce was investigated. Iceberg lettuce cv. Sahara grown at the University of Arizona Yuma Agricultural Center was evaluated for yield, microbial population and postharvest quality either following different irrigation termination schedules or before/after a rainfall event. We report here microbial population data with treatments including early (16 days before harvest), middle (8 days before harvest) and late (4 days before harvest) irrigation termination. Lettuce receiving the last irrigation 4 days before harvest showed increased weight but had higher microbial population than other treatments. The effect of moisture prior to harvest on quality was further evaluated with lettuce harvested before and after a rainfall event. Increased aerobic bacteria population of over 1 log CFU/g for outer leaves and over 2 log CFU/g for head leaves was observed after rain. The results from this study suggest that managing moisture conditions at harvest is important to enhance quality of lettuce.
    • Yield and Postharvest Quality of Cantaloupe Melons as Affected by Calcium Foliar Applications

      Fonseca, Jorge; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      The effect of pre-harvest foliar application of calcium on yield and postharvest quality of whole and fresh-cut cantaloupe melons was investigated. The calcium product (Nutrical®) was applied five times before harvest to a melon field at 2 quarts/acre with a volume of 50 gallons/acre. The supplemented calcium increased by over 10% the weight of melons and increased external firmness at harvest but soluble solids was lower in treated melons than in the control. After 21 days of storage at 40 - 45 °F however, there was not difference in quality factors. Melons were processed in cubes and packaged in plastic lidded containers. The overall quality of calcium treated cubes was better after 5 and 10 days of storage. Juice leakage was also higher in the control than in the treated fruits after 5 days. After 10 days the L* values were lower in the control than in the treated fruits indicating that the tissue was darker in the control, which was an indicative of more water soaked tissue. In further trials conducted the following Spring the results obtained at harvest showed differences only in weight of melons that underwent water stress. The overall results in different experiments in the Yuma area indicate that application of foliar calcium can increase yield of melon crops, notably, when the plants undergo environmental stress.