Genotype Is Primarily Responsible for Variance in Table Beet Geosmin Concentration, but Complex Genotype × Environment Interactions Influence Variance in Total Dissolved Solids

Abstract

Earthy aroma and sweet flavor, conferred by the volatile terpenoid geosmin (trans-1,10-dimethyl-trans-9-decalol) and sucrose, respectively, are two essential flavor components of table beet (Beta vulgaris ssp. vulgaris). To elucidate the influence of genotype, growing environment, and fertilizer treatment on geosmin concentration and sucrose [as total dissolved solids (TDS)] in table beet, a field-based genotype × environment study was conducted using a split-split plot design. Four site × year combinations served as whole plots; MgSO4·H2O and CaSO4 comprised split plot fertilizer treatments; open-pollinated cultivars Bull’s Blood and Touchstone Gold, F1 hybrid Merlin, and inbred line W357B constituted split-split plot genotype treatments. Geosmin concentration was measured via gas chromatography–mass spectrometry using headspace solid-phase microextraction, and TDS was measured via refractometry. Variation in geosmin concentration was attributable to a strong genotype effect and significant genotype × year and year × site interactions. Genotypes were observed to have characteristic geosmin concentration and variance, despite being grown in soils with widely divergent physical and chemical properties. While a significant genotype main effect was also present for TDS, it occurred in the context of significant four-way and three-way genotype × environment interactions, plus significant effects of year and year × site interaction. Neither geosmin concentration nor TDS was significantly influenced by fertilizer treatment or fertilizer × environment interactions, averaged across genotypes. Genetics determined a larger proportion of variance for geosmin concentration than TDS in the four table beet genotypes assessed, as reflected in repeatability measurements of 0.90 and 0.43, respectively. This experiment provides support for the primacy of genotype in determining table beet geosmin concentration and a comparatively moderate role of genotype in determining table beet TDS. Thus, genetic manipulation of table beet geosmin could yield cultivars with signature flavor characteristics to serve both niche and mainstream consumer groups, expanding market opportunities for breeders and growers.