Relationships between productivity and carbon isotope discrimination amongdry bean lines and F-2 progeny

Common bean (Phaseolus vulgaris L.) and tepary bean (P. acutifolius Gray) a re grown for their edible seed and production is limited by insufficient so il moisture in many parts of the world. Carbon isotope discrimination (a) a gainst (CO2)-C-13 during photosynthesis has been suggested as a useful sele ction criterion to improve crop productivity in water-limited environments, however, there is a need to first understand relationships between product ivity and Delta in common bean. The objectives of this study were to: 1) ev aluate relationships between productivity (as measured by seed yield and bi omass) and a among diverse dry bean lines and F-2 progeny, 2) evaluate asso ciations for a, seed yield and biomass among lines grown in different field environments and 3) estimate narrow sense heritability for Delta, seed yie ld and yield components. One hundred dry bean lines were evaluated at Yello w Jacket, CO in irrigated and non-irrigated field plots during 1988 and 198 9. All significant relationships between seed yield or biomass and Delta we re positive. In general, relationship between seed yield and Delta among li nes were weak and R-2 ranged from near zero to 0.29 across years and enviro nments. 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 w ere 0.78 and 0.75, respectively. These results support the positive relatio nship between productivity and Delta in bean, however, the weak relationshi ps between a and seed yield do not suggest that Delta would be a useful sol e selection criterion to improve productivity.