Black spruce extracts reveal antimicrobial and sprout suppressive potentials to prevent potato (Solanum tuberosum L.) losses during storage

Canadian forest residues, such as bark, are an abundant and accessible biomass currently burned to produce energy, therefore neglecting their great potential for various applications owing to their multiple biological properties. Potato storage constitutes a challenge for potato producers because of disease propagation and potato sprouting. Barks appear to be promising candidates in the research of greener alternatives to synthetic chemicals presently used to limit these problems. Hence, this study aimed to develop a bio-based ingredient from bark residues to prevent diseases and sprouting of potatoes during storage. First, forest extracts were produced from the bark of black spruce (Picea mariana Mill.), balsam fir (Abies balsamea L. Mill.) and yellow birch (Betula alleghaniensis Britton) by three different methods: water extraction, ethyl acetate fractionation of the water extract, and acid-base extraction. Then, in vitro screening of extracts and commercial essential oils was performed to determine their ability to inhibit potato soft and dry rot and potato sprouting. More specifically, Fusarium oxysporum, Fusarium graminearum, Fusarium sambucinum, Pectobacterium atrosepticum, Pectobacterium carotovorum, and Dickeya dianthicola were selected for antimicrobial assays. Two black spruce extracts, ethyl acetate extract and essential oil, showed promising antimicrobial and anti-sprouting properties. The black spruce ethyl acetate extract inhibited microorganism growth with minimum concentrations ranging from 1.37 × 10–³ to 3.00% (w/w) depending on the strain. Black spruce essential oil completely prevented potato sprouting in Colomba cv. at a minimal concentration of 25% (w/w). Furthermore, when mixed, both properties were maintained, and even showed a synergistic effect. Indeed, in antimicrobial assays, the fractional inhibitory concentration index obtained was lower than 0.50. Therefore, these two black spruce extracts can be formulated into one product with broad properties aimed at controlling potato post-harvest losses due to rot and sprouting.