Relationship between secondary traits and grain yield of maize in low nitrogen soils in Malawi
1997
Sibale, E.M. | Smith, M.E.
Grain yield is an important criterion for selecting for tolerance to low nitrogen (N) in maize, but there are limitations to its use due to large genotype by environment interactions. There is need to identify alternative traits less prone to alterations by the environment, which breeders can use to select for tolerance to low N in maize. The objective was to identify traits that can be used to screen for tolerance to low N. Divergent selections for chlorophyll concentration were made in S2 lines from two maize populations grown at 0 and 80 kg N ha-1. Chlorophyll measurements were made using a hand-held Minolta SPAD-502 chlorophyll meter. Plants with chlorophyll readings above and below the plot mean reading were selfed. Crosses were made between S3 lines with large chlorophyll readings, small chlorophyll readings, and between lines with large and small chlorophyll levels, both within and between the two populations. Resulting hybrids were evaluated at 0, 40, and 80 kg N ha-1. Chlorophyll readings of hybrids were not significantly different among N levels at the five-leaf stage, but differed significantly at flowering. Selections for high and low chlorophyll readings made under low N were not significantly different from selections made under high N when their hybrids were evaluated at different N levels. There were significant genotype-by-nitrogen interactions for chlorophyll at flowering, days to mid-silk, anthesis-silking interval, ear height and grain yield. Chlorophyll at flowering, days to mid-anthesis, days to mid-silk, test weight and number of kernels per ear were significantly correlated with grain yield at 0 kg N ha-1.
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