Genetic variation for nitrogen use efficiency in a set of recombinant inbred lines II - QTL detection and coincidences

The development of varieties with a better nitrogen use efficiency (NUE) is a means for modern agriculture to decrease environmental pollution by nitrates and to maintain a sufficient net income. Such development will be more efficient if the genetic basis of NUE is known. QTLs for vegetative development, grain yield and its components and grain composition (starch, protein, amino acids) were studied with and without nitrogen fertilization (N+ and N-), using a set of 99 recombinant inbred lines crossed to a tester. QTLs for traits of vegetative development, grain yield and its components were grouped in clusters. For such traits, more QTLs were detected in N+ than in N-, and QTLs in N- were a subset of QTLs in N+. Only some QTL x N level interactions were detected. For grain protein content, more QTLs were detected in N- than in N+. All these detected N- QTLs coincided with QTLs detected for vegetative development and grain yield in N+. QTLs for N-uptake were mainly detected in N+, whereas QTLs for nitrogen utilisation efficiency were mainly detected in N-. As a whole, genetic variability was expressed differently in N+ and N-. Several coincidences between genes encoding for enzymes of N and C metabolism and QTLs for vegetative development and grain yield and its components were observed. This was the case for genes of glutamine synthetase, ADPGppase, sucrose phosphate synthase, sucrose synthase and invertase. All coincidences were consistent with the expected physiological effects of such genes which appear to be good candidate genes for QTLs of grain yield and its components.