Relationships between productivity and carbon isotope discrimination among dry bean lines and F2 progeny

Common bean (Phaseolus vulgaris L.) and tepary bean (P. acutifolius Gray) are grown for their edible seed and production is limited by insufficient soil moisture in many parts of the world. Carbon isotope discrimination (a) against (CO2)-C-13 during photosynthesis has been suggested as a useful selection criterion to improve crop productivity in water-limited environments, however, there is a need to first understand relationships between productivity and Delta in common bean. The objectives of this study were to: 1) evaluate relationships between productivity (as measured by seed yield and biomass) and a among diverse dry bean lines and F-2 progeny, 2) evaluate associations for a, seed yield and biomass among lines grown in different field environments and 3) estimate narrow sense heritability for Delta, seed yield and yield components. One hundred dry bean lines were evaluated at Yellow Jacket, CO in irrigated and non-irrigated field plots during 1988 and 1989. All significant relationships between seed yield or biomass and Delta were positive. In general, relationship between seed yield and Delta among lines were weak and R-2 ranged from near zero to 0.29 across years and environments. The correlations for Delta, seed yield and biomass production among lines grown in different environments were all significant and positive (0.76 > r > 0.36). Narrow-sense heritability estimates for a and seed yield were 0.78 and 0.75, respectively. These results support the positive relationship between productivity and Delta in bean, however, the weak relationships between a and seed yield do not suggest that Delta would be a useful sole selection criterion to improve productivity.