Chapter 6 - Molecular genetics to discover and improve nitrogen use efficiency in crop plants

Abstract

Worldwide, over 100 million tonnes of nitrogen (N) fertilizer is applied each year to maximize yields of agricultural crops and this is a major cost for farmers. Inefficient use of N fertilizer, as well as being an economic cost, leads to substantial environmental problems. Consequently, there is urgent need to improve the way N fertilizer is used in farming systems. The efficiency in which crops use applied N fertilizer, the nitrogen use efficiency (NUE), is currently poor for cereals. Multiple studies have attempted to identify the genetic basis of NUE but the utility of the results is limited because of the complex nature of the trait and the magnitude of genotype by environment interaction. Transgenic approaches have been applied to improve plant NUE but with limited success, perhaps due to combination of the complexity of the trait but also due to lack of accurate phenotyping methods. This chapter documents these two approaches and suggests future directions in improving NUE in crops.