Biological nitrogen fixation and assimilation of CO₂ can be indirectly monitored in alfalfa (Medicago sativa L.) through the variation of the stable N and C isotopes in the plant (D values). Such measurements result in a simple, non-destructive and reliable method for identification of alfalfa cultivars of high yield and nutritional quality. Plant properties that indicate its yield potential and quality are associated with common agronomic traits such as dry matter, digestibility and protein content. In alfalfa the biologic nitrogen fixation, measured via the isotopic discrimination, allows the identification of more efficient plants for the formation of nitrogen compounds, which influence the biomass production (Oliveira, 1999). Likewise, the photosynthetic capacity, measured via the carbon isotopic discrimination, allows the identification of more efficient plant for the maximization of the stomatal opening, which regulates the biomass production (Farquhar et al., 1989).A selective program that studied twelve different cultivars of alfafa, including dorments and non-dorments varieties, was initiated in 1997 at the ESALQ/USP field station and CENA/USP laboratories, Piracicaba, SP, Brazil. Under controlled conditions significant variations (p<0.05) were observed for all agronomic and physiological traits for 12 alfalfa cultivars.

Previous Page