Protein and Mineral Composition of Tepary Bean Seed

Abstract

Tepary bean (Phaseolus acutifolius A. Gray), a native of southwestern U.S., is a promising plant for crop diversification and for production in short rotations with wheat. However, protein and mineral concentrations in tepary bean seed produced outside the southwestern U.S. are largely unknown. We evaluated concentrations of protein and various minerals in seed produced by eight tepary bean genotypes planted at three different dates each during 1997 and 1998 at Ettrick, Virginia. Significant year × planting date and year × genotype interactions existed for protein and other traits. Protein and zinc concentrations increased and calcium concentrations decreased with later plantings during both years. Mid-June planting had 14% higher protein concentration (24.5%) than late-May planting (21.4%) and mid-July planting had 6% higher protein concentration (25.9%) than mid-June planting. Color of seedcoat was not associated with concentrations of protein or minerals. The average concentrations of boron, calcium, copper, iron, potassium, magnesium, manganese, phosphorus, sulfur, and zinc (mg/100g) were: 1, 184, 1, 11, 1531, 192, 3, 451, 311, 4, respectively. Tepary bean seeds contained 24% protein as compared to reported average values of 22.3% in navy, 22.5% in red kidney, and 20.9% in pinto bean. The average iron concentration (mg/100g) in tepary bean seed (10.7) was higher than that in navy (6.4), red kidney (6.7), and pinto (5.9) bean. Based on protein and mineral concentrations tepary bean seed compared well with seeds of navy, red kidney, or pinto bean.