Strawberry fruit were harvested on three different dates from the Strawberry Association plot (cv. Festival), a commercial farm (cv. Camino Real), and at the University of Florida Gulf Coast Research and Education Center (cv. Sweet Charlie), in central Florida in 2005 and 2006. Fruit were transported to the USCSPL in Winter Haven, Fla., sorted, dipped for 10 s in treatment solutions, drained and stored in commercial clam-shells at 15 to 19 °C. Percentage of decay (number of fruit with lesions) was monitored during storage. There were 10 fruit per replicate clamshell, and three to four replicates per treatment for each harvest. Treatments included three size classes of galacturonic acid (GA) oligomers with a degree of polymerization (DP) ranging from 1–13, 8–24, and 22–46 and undigested polygalacturonic acid at 0.2% in 50 mmol LiOAC, LiOAC/NaOAC, with 22% ETOH, or KOAC buffer (all buffers at pH ≈4.4), prepared by enzymatic digestion followed by differential pH and alcohol precipitation. The main pathogens found on these fruit were Rhizopus stolonifer and Botrytis cinera at 1×105 cfu/g fruit in 2005 and 5×107 in 2006. The medium range oligomers (DP 8-24) reduced decay significantly compared to buffer alone or to the lower or higher DP GA oligomers, and elicited ethylene production. Oligomers in this pectin size class have previously been reported to elicit ethylene and plant defense responses in plant tissues.
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