HPLC-MS Metabolomics Reveals No Significant Impact of Microbial Inoculation with Bacillus velezensis and Lachnum sp. on Cranberry Metabolome

Abstract

Sustainable agriculture has driven the increased exploration of microbial inoculants as a promising strategy to promote plant growth, improve crop yield, and stimulate secondary metabolism to enhance crop nutritional quality. However, the influence of microbial inoculation on the cranberry fruit metabolome under field conditions remains poorly understood. This study investigated the effects of inoculating cranberry (Vaccinium macrocarpon) plants with Bacillus velezensis EB37 and Lachnum sp. EC5, applied individually and in combination, on cranberry fruit phytochemistry. Over two harvest years (2019 and 2021), cranberries were collected from treated and control plots and analysed using untargeted and targeted HPLC-MS-based metabolomics. Untargeted metabolomic analysis revealed no significant treatment-associated differences in the cranberry fruit metabolome. Instead, samples clustered strongly by harvest year, indicating that annual environmental variation had a greater influence on metabolite composition than microbial inoculation. Targeted quantification of six representative phenolic compounds (chlorogenic acid, catechin, p-coumaric acid, phloridzin, myricetin, and quercetin) likewise showed no significant differences between treated and untreated cranberries. These findings indicate that microbial inoculation alone does not substantially alter the cranberry fruit metabolome, including major phenolic compounds, under field conditions. This study underscores how multiple factors, such as environmental conditions, can affect the outcome of microbial inoculation under field conditions and suggests that additional interventions may be required to achieve microbiome-based improvements in cranberry fruit quality.