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 nitr ates and to maintain a sufficient net income. Such development will be more efficient if tile genetic basis of NUE is known. QTLs for vegetative devel opment, grain yield and its components and grain composition (starch, prote in, amino acids) were studied with and without nitrogen fertilization (N+ a nd N-), using a set of 99 recombinant inbred lines crossed to a tester. QTL s for traits of vegetative development, grain yield and its components were grouped in clusters. For such traits, more QTLs were detected in N+ than i n N-, and QTLs in N- were a subset of QTLs in N+. Only some QTL x N level i nteractions were detected. For grain protein content, more QTLs were detect ed in N- than in N+. All these detected N- QTLs coincided with QTLs detecte d for vegetative development and grain yield in N+. QTLs for N-uptake were mainly detected in N+, whereas QTLs for nitrogen utilisation efficiency wer e mainly detected in N-. As a whole, genetic variability was expressed diff erently in N+ and N-. Several coincidences between genes encoding for enzym es of N and C metabolism and QTLs for vegetative development and grain yiel d and its components were observed. This was the case for genes of glutamin e synthetase, ADPGppase, sucrose phosphate synthase, sucrose synthase and i nvertase. All coincidences were consistent with the expected physiological effects of such genes which appear to be good candidate genes for QTLs of g rain yield and its components.