High microbial diversity in the rhizosphere and soil improve carrot (Daucus carota L.) postharvest storability

Postharvest diseases can cause significant losses in carrot (Daucus carota) yield during storage. In this study, the effects of soil quality and microbial diversity in the field bulk soil and rhizosphere on the development of postharvest diseases were investigated. Microbial genera in bulk soil and rhizosphere samples were identified by Illumina Miseq amplicon sequencing of bacterial 16S and fungal ITS regions. Disease symptoms in the stored carrots were monitored after six months of cold storage, and the main pathogens were identified. The field sites with mineral soils, which had a higher pH, had a higher bacterial and fungal diversity than organic soils. The organically managed fields had a higher bacterial diversity than the conventionally managed fields. Community structure of both bacteria and fungi was largely driven by field site including its main chemical characteristics, with rhizosphere and bulk soil samples from the same site displaying comparable assemblages. Higher soil microbial diversity was associated with higher postharvest storability in the stored carrots. The weather during the growing season also had an effect on the observed fungal biodiversity, which was higher at sites that had lower temperatures and less rain prior to harvest.