Effects of stabilizers on shelf-life of Epicoccum nigrum formulations and their relationship with biocontrol of postharvest brown rot by Monilinia of peaches

Abstract

Aim: To find a formulation of Epicoccum nigrum conidia that maintains a high viability over time and which proves efficient to biocontrol peach rot caused by Monilinia spp. Methods and Results: We tested the effect of stabilizers and desiccants on the shelf-life of Epicoccum nigrum conidia. Conidial samples were dried for 40 min at 40°C in a fluidized bed-dryer to obtain moisture contents <15%. The toxicity of additives was tested by assaying production of conidia in fermentations and germinability of the produced conidia: 50% PEG300, 10%-5% KCl (stabilizers) and 95.24% Cl 2Ca (desiccant) significantly (P = 0.05) reduced conidial germination. To enhance shelf-life of dried conidia, nontoxic stabilizers were added at the following different stages of the production-drying process: (i) to substrate contained in bags before production, (ii) to conidial centrifuge pellets obtained after production, before filtering and drying, (iii) to conidial centrifuge pellets obtained after production, before adding talc and drying, and (iv) to conidial centrifuge pellets obtained after production, before adding silica powder and drying. Conidial germinability was tested at 0, 180 and 365 days after storage at room temperature. Shelf-life of formulations retaining the highest viability were conidia produced with 1% KCl or 50% PEG 8000, conidia dried with 2.5% methylcellulose, and conidia dried with 1% KCl + silica powder. All these formulations improved the shelf-life of E. nigrum conidia and significantly reduced brown rot on peaches. Conclusions: Our results show that additives improve the shelf-life of E. nigrum and assist controlling brown rot on peaches. Significance and Impact of the Study: New improved formulations of a biocontrol agent have been obtained which will improve the control of Monilinia on peach. © 2007 The Authors.