2018 ASHS Annual Conference

The flavor profile of table beet is dominated by the earthy-flavored terpene derivative geosmin. Geosmin can be a desired characteristic in beet or a deterrent to the consumption of the vegetable. Geosmin is also produced by Streptomyces spp., various cyanobacteria, and fungi often found in soil and water environments. A long-held presupposition suggests that geosmin production in beets is due to an association with geosmin-producing microbes in the soil. Four beet accessions were grown in an aseptic tissue culture environment. Lack of microbial contamination was demonstrated by sequencing 16S ribosomal RNA to identify potential contaminating microbes. Operational taxa units (OTUs) returned from this analysis were identified as either chloroplast (98%) or mitochondria (2%), demonstrating that beet plants free of microbes were capable of endogenous geosmin production. Bidirectional half-sib recurrent selection for geosmin concentration over four breeding cycles resulted in the development of low (LGC) and high (HGC) geosmin concentration populations. From Year 1 to Year 3, the LGC mean shifted from 17.3 to 4.3 µg geosmin kg–1 tissue and the HGC mean shifted from 22.3 to 33.8 µg geosmin kg–1 tissue. Taken together, these results demonstrate that geosmin is endogenously produced by beets and is responsive to selection, making it another target trait for breeding.