Response of low-N pool maize population to nitrogen uptake and use efficiency after three cycles of full-sib recurrent selection

Abstract

SUMMARYIdentification of plant cultivars efficient for nitrogen (N) uptake and utilization may contribute to the improvement of crop yield potential in areas of low-N (LN) availability. Three cycles of full-sib recurrent selection were applied on a LN pool-yellow (LNP-Y) maize population to improve its level of tolerance to low soil N in the savannah ecosystem. The progress after three cycles of selection was evaluated for two years (2000 and 2001). The objectives of the study were to classify the cycles in relation to response to N levels under field conditions and to investigate the progress in selection for improved grain yield and other agronomic traits at two N levels, LN (30 kg N/ha) and high-N (HN, 90 kg N/ha). The experiment was conducted under field conditions at the LN screening site of the Institute for Agricultural Research, Samaru, in the northern Guinea savannah of Nigeria. The experimental design consisted of randomized complete blocks with three replications. The aboveground biomass and grain at harvest were analysed for total N content. The results indicated differences in plant population response to N levels. Mean grain yield ranged from 2·5 t/ha in cycle 1 to 2·7 t/ha in cycle 3 under LN and from 4·2 t/ha in cycle 1 to 4·3 t/ha in cycle 3 under HN. The observed gains were 4·8% per cycle under LN and 1·4% per cycle under HN. Nitrogen use efficiency (NUE) traits, viz. N uptake efficiency and N utilization efficiency were positively affected by selection. Gains for N utilization efficiency were 6·3% per cycle at LN and 9·1% per cycle at HN, while observed gains for NUE were 3·9% at LN and 1·4% per cycle at HN. However, N utilization efficiency was identified as the most important component of NUE for selecting cycles of selection in population development. Total N content and N utilization efficiency were significantly correlated with each other at LN, and had a significant, positive, direct effect on grain yield. Grain yield was positively correlated with N content and N utilization efficiency at both N levels. Also, a significant positive correlation was observed at LN between 300 kernel weight and N utilization efficiency. N utilization efficiency was correlated with ears/plant at HN and negatively correlated with anthesis-silking interval (ASI). The present study revealed that selection for improved productivity under LN stress conditions could be further enhanced by simultaneously selecting for high grain yield performance based on N utilization efficiency and on secondary traits, such as ears/plant, 300 kernel weight, and reduced ASI.