From seed to storage: disease management in organic beetroot production to reduce food wast

The market for organic agriculture is rapidly growing. In Switzerland, the production of organic Beetroot is particularly renowned. However, their storage until spring has become increasingly difficult in recent years, and losses due to post-harvest rots can lead to over 50 % by March. Consequently, most organic beetroots sold in spring need to be imported if the previous season was poor. The causes of the various storage rots in beetroot are currently unclear, and therefore there are few measures to prevent them in organic production. Pathogen infections causing storage rots in beetroot, but also in other long-stored vegetables, can occur via the seed, in the field, or post-harvest. Understanding the process of infection is, therefore, critical to find preventive solutions. Here, we present the results of a three-year project aiming at reducing post-harvest losses in organic beetroot production. In a combination of on-farm field experiments and laboratory analyses, we aimed to elucidate the causes of storage rots in organic beetroot and develop measures to improve storability. Analysis of stored beetroot in 2021, 2022 and 2023 revealed Phoma betae, Fusarium sp. and Plectosphaerella sp. as predominant pathogens in Switzerland. Plectosphaerella sp. was never identified before on beetroot. Mortierella, Mucor and Alternaria were found to be additional causative agents of storage rots. Seeds analysis highlighted the same pathogen identified on the rotting tuber (Alternaria sp., Phoma betae and Fusarium sp.), suggesting that the possible cause may come directly from the seeds. Different measures, such as steam sterilization of the seed, the use of biocontrol products in the field and before storage, or processing and cooling methods after harvest, as well as cultivar differences were investigated. Various measures were found to affect seed health, seedling emergence, leaf health, and the quality of beetroot after storage.