Todd C. Wehner

Heritability estimates of traits assist breeders in optimizing cultivar development and can help predict gain from selection in breeding programs. Narrow‐sense heritabilities were measured in agronomic traits and glycoside concentration in four elite stevia ( Stevia rebaudiana Bertoni) populations using half‐sib family analysis. Gain from selection at 20% selection intensity was estimated for morphological, yield, and glycoside traits. Experiments were conducted in two field locations in North Carolina. Variation was observed across cultigens for agronomic traits including stem height, branch width, and leaf size, for both subjective and objective measurements. Yield, lodging resistance, disease resistance, and percent survival showed a high genetic variation across cultigens. In addition, glycosides including Reb A, Reb C, and Reb D also showed high variation by cultigen. Heritability estimates for plant morphological traits were highest for stem height, and moderate for yield and branch width. However, other traits such as leaf area and lodging resistance showed low heritability (0.10). Glycosides including Reb A, Reb C, Reb D, stevioside and total steviol glycosides (TSG) showed high heritability. The estimated gain from selection per year for stem height (24 mm/year), leaf area (131 mm 2 /year) and yield (dry weight) (1.2 Mg/ha per year) suggest significant improvements are possible per breeding cycle. The estimated gain for glycoside concentration and percent of TSG of Reb A (26.44 mg/g, 14.51%), Reb C (20.20 mg/g, 20.17%), Reb D (1.70 mg/g, 1.49%), stevioside (6.73 mg/g, 10.72%), and TSG (20.90 mg/g), similarly, indicate significant gains are possible per breeding cycle.