Improvement for tolerance to low soil nitrogen in tropical maize III. Variation in yield across environments uri icon


  • An analysis of yield components and N concentrations in plant parts indicated that yield variation in C1 (the selection cycle which had the greatest variation among environments) was associated with an over-investment in preflowering vegetative biomass, without a concomitant increase in post-flowering grain sink size. By C3, the number of kernels plant-1 had been increased, but yield apparently was limited by inadequate source capacity in the latter stages of grain-filling. Cycle 3 also produced 25% more root biomass than C0 when grown with adequate N supply in pots, while aboveground biomass increased by a smaller proportion (9%). Changes in biomass partitioning to roots may be an important adaptation to low-N environments.
  • Correlation analysis of the data collected indicated that some relationships among traits thought to be important to performance differed in magnitude and sign among environments. For example, a positive correlation was observed between grain yield and preflowering N accumulation in the high-N environments, but no association was observed among these traits at low N. Correlations also differed significantly among seasons within an N level for some traits. For example, the correlation between final grain N concentration and N floret-1 at flowering under low N was 0.97 (P < 0.03) in one season, and that correlation was - 0.98 in a subsequent season.
  • These results indicate that seasonal differences in the timing and magnitude of N and C supply play a large role in determining the adaptive value of a given trait, even when environments may be similar in the amount of N applied to, or absorbed by, the crop. Selection for increased yield under low N apparently perturbs the balance of source and sink compared with selection under nonlimiting N levels, and extensive testing in environments differing in C and N abundance seems essential to establishing progress from such breeding schemes. In addition, more effort to quantify the extent and timing of N stress in each season appears justified.
  • When improving grain yield of maize (Zea mays L.) grown under low soil N by recurrent selection, it is desirable to maintain or increase the stability of performance across sites differing in N status. The objective of this study was to identify the possible causes of increased variation in grain yield with selection for tolerance to low soil N in four cycles of selection (C0 to C3) of the lowland tropical maize population, Across 8328 BN, when grown in 12 irrigated environments characterized by different radiation and N availabilities. Yield components and patterns of biomass and N partitioning were examined.

publication date

  • 1994
  • 1994