Beta vulgaris ssp. vulgaris chromosome 8 shows significant association with geosmin concentration in table beet

Abstract

Geosmin, a degraded sesquiterpene molecule with earthy and musty odor, imbues table beet with its characteristic aroma. Geosmin is heritable and endogenously produced in table beet; its earthy aroma is sought by some consumers but deters others. Geosmin biosynthesis is catalyzed by a bifunctional geosmin synthase enzyme in diverse bacteria and fungi, but a mechanism for geosmin biosynthesis in plants has not been reported. This work employed association analysis and selective genotyping of a segregating F2:3 mapping population to seek QTL associated with geosmin concentration in table beet. GBS reads were aligned to sugar beet reference genome EL10.2, and association analysis revealed two QTL for geosmin concentration on B. vulgaris ssp. vulgaris Chromosome 8. QTL at EL10.2 positions 28,017,624 and 38,488,687 each show effect size 8.7 μg · kg-1 geosmin and explain 8.5% and 6.4% of total variation in geosmin concentration, respectively. Resolution was low due to large recombination bin size and imperfect alignment between the reference genome and mapping population, but population size and selection proportion were sufficient to detect moderate to large effect QTL. This study, the first molecular genetic mapping experiment in table beet, succeeded in finding QTL for geosmin concentration in table beet, and it provides the basis for fine mapping or candidate gene investigation of functional loci for this distinctive sensory trait.

Novel QTL associated with Rhizoctonia solani Kühn resistance identified in two table beet × sugar beet F2:3 populations using a new table beet reference genome

“…More recently, researchers have investigated flavor characteristics, namely the earthy flavor imparted by the compound geosmin. In the first genetic mapping experiment in table beet, Hanson et al (2021) used association analysis and selective genotyping to search for QTL associated with geosmin concentration. Large portions of chromosome 5 were significantly associated with the production of this volatile terpenoid (Hanson et al, 2021).…”

“…(Nilsson et al., 1999; Schäfer‐Pregl et al., 1999; Setiawan et al., 2000; Taguchi et al., 2011). MAS has already been utilized in sugar beet to select for resistance to some diseases as well as for reproductive traits such as CMS (Moritani et al., 2013); however, use of the technology for host resistance has not yet been reported in table beet, and thus far, only a single marker−quantitative trait loci (QTL) association for geosmin concentration has been reported in table beet (Hanson et al., 2021).…”

A terpene cyclase from Aspergillus ustus is involved in the biosynthesis of geosmin precursor germacradienol

“…2 Other organisms like mould fungi, arthropods, nonvascular plants (liverworts), vascular plants (red beet, cactus ower), basidiomycetes and amoebae were also reported to be able to produce geosmin. [3][4][5] Geosmin is found as a common contaminant of drinking water, wine and bioaccumulates in sh leading to a musty taste. Geosmin in water and sh usually originates from microbes.…”

Participatory plant breeding reveals that geosmin concentration is not the central determinant of hedonic liking in table beet

“…Hartke 2020), as has the range of consumer attitude toward earthy flavor in beet: from adoration to aversion. Because earthy flavor deters some consumers from beets, and because geosmin is known to produce earthy aroma, research has been undertaken to determine the degree to which geosmin concentration in table beet is genetically controlled (Freidig and Goldman 2014;Maher andGoldman 2017, 2018;Hanson and Goldman 2019;Hanson et al 2021). In addition, OP cultivar 'Badger Flame' was developed by Goldman and Breitbach at UW-Madison for low levels of earthy flavor-albeit without laboratory measurement of geosmin concentration-and consumer response to the cultivar has been positive (Rao 2018) et al 2004).…”

“…ions and 15-carbon precursor molecule farnesyl diphosphate (FPP) (Jiang et al 2007). A geosmin synthase gene has been discovered in both Streptomyces coelicolor (Cane and Watt 2003) and cyanobacteria (Giglio et al 2008, Churro et al 2020 (Hanson et al 2021). In addition, a preliminary search of the RefBeet sugar beet reference genome (Dohm et al 2014) for the S. coelicolor geosmin synthase sequence returned two hypothetical proteins with predicted terpenoid synthase function (Huang et al 2017) also located on B.vulgaris Chromosome 8 (Maher 2017).…”