Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/2/2008
Publication Date: 10/1/2008
Citation: Usall, J., Smilanick, J.L., Palou, L., Teixido, N., Torres, R., Vinas, I. 2008. Preventive and curative activity of combined treatments of sodium carbonates and Pantoea agglomerans CPA-2 to control postharvest green mold of citrus fruit. Postharvest Biology and Technology. 50(1):1-7. Interpretive Summary: Citrus fruit rot after harvest, usually by the action of fungal pathogens. To control these losses, fungicides are typically used. Alternatives to fungicides were developed in this work that consisted of a combination of a heated sodium bicarbonate treatment followed by the application of a biological control bacterium. This report contributes to the development of practical technologies to reduce postharvest fruit losses without the use of synthetic fungicides.
Technical Abstract: Preventive and curative activity of 2 min dips in 3% sodium carbonate (SC) or sodium bicarbonate (SBC) aqueous solutions heated to 40ºC, alone of followed by the application of 2 x 108 CFU/ml of the biocontrol agent Pantoea agglomerans CPA-2 (BA), in the control of postharvest green mold, caused by Penicillium digitatum, were simultaneously evaluated in artificially noculated Lanelate and Valencia oranges. Fresh cells of BA proliferated inside rind wounds and their survival was not adversely affected by the presence of residues of SC or SBC. Green mold incidence after 7 days of incubation at 20ºC in rind wounds treated after fungal inoculation (curative activity) was 15, 40, and 15% in oranges treated with SC, BA, and SC+BA and 5, 45, and 0% in oranges treated with SBC, BA, and SBC+BA, respectively, while it was about 90% in untreated control fruit. Green mold incidence in rind wounds treated before inoculation or reinoculation with the pathogen (preventive activity in pre-existing wounds) was 10 and 2%, or 15 and 8%, respectively, in oranges treated with SC and SC+BA, and 3 and 5% or 20 and 5%, respectively, in oranges treated with SBC and SBC+BA. Green mold incidence in rind wounds inflicted and inoculated after treatment (preventive activity in new wounds) was 55 and 25%, and 60 and 40% in oranges treated with SC and SC+BA, and SBC and SBC+BA, respectively. Additionally, the duration of the protective effect of SBC, BA, and SBC+BA was assessed in Eureka lemons and Valencia oranges. In both species, all three treatments effectively protected pre-existing rind wounds for 7 days of storage at 10ºC. After 0, 1, and 2 days, but not after 4 or 7 days, the protective effect of SBC was significantly inferior to that of BA and SBC+BA. As a conclusion, the integration of treatments showed the potential to replace the use of conventional fungicides against green mold in citrus packinghouses.