Genetic variation in the prebiotic carbohydrate and mineral composition of kale (Brassica oleracea L. var. acephala) adapted to an organic cropping system

Abstract

Kale is a nutrient-rich leafy green that is mostly grown in conventional agricultural systems. The demand for organic kale has increased in the U.S.; however, cultivars bred for conventional production are not suited to organic production in terms of yield and nutritional quality. The objective of this study was to evaluate the genetic variation in biomass, prebiotic carbohydrates, and minerals of 18 commercial cultivars and 35 PI accessions of kale adapted to the organic system. Significant genetic variation in both prebiotic carbohydrates and minerals was noted in both kale cultivars and PI accessions. In the kale cultivars, leaf biomass ranged from 41.4–271.2 g/plant, with kale cultivar “Frizzy Joe” being the highest and “Fizz” the lowest. A single 100-g serving from these kale cultivars provides mineral micronutrients (20–314 mg K; 95−539 mg Ca; 20−67 mg Mg; 13−87 mg P; 0.4−3.1 mg Fe; 0.3−0.9 mg Zn; 0.4−1.9 mg Mn; 20−1030 μg Cu; and 0–940 μg Se) and prebiotic carbohydrates, including sugar alcohols (1.7–26.9 mg), simple sugars (0.03–334 mg), and raffinose and fructooligosaccharides (0–11.2 mg). Compared to the commercial cultivars, the kale accessions had higher concentrations of minerals, except for magnesium (Mg) and manganese (Mn), and prebiotic carbohydrates, except for sucrose and verbascose + kestose. In the commercial cultivars, heritability estimates for prebiotic carbohydrates and minerals were relatively low except for sugar alcohols, Mg, and zinc (Zn). In the kale accessions, heritability estimates of glucose, fructose, potassium (K), and selenium (Se) were high. Overall, significant genetic variation exists among kale commercial cultivars and germplasm for prebiotic carbohydrates and minerals, indicating the nutritional quality of kale in organic production can be further improved by germplasm selection.