Plant breeding for efficient plant use of nitrogen

This chapter outlines standard corn-breeding procedures that can be adapted to the use of physiological and biochemical traits. It reviews interrelationship between N, nitrate reductase, and yield of grain and grain protein. The chapter discusses preliminary results obtained when biochemical and physiological traits were used in conjunction with phenotypic recurrent divergent selection and mass selection with half-sib families. It describes a hypothetical ideotype corn plant with the potential for efficient conversion of fertilizer N to yield. Although in cereal crops, potential grain yield may be affected by the availability of N at various stages of plant growth, the effects of N are confounded by interactions with other nutrients and metabolic systems, especially C metabolism. The two projects concern specific attempts to utilize physiological and biochemical traits associated with N metabolism as the selection criterion in standard breeding procedures. These are selection for nitrate reductase activity and correlated response to selection.