Francisco Miti, Pangirayi Tongoona and John Derera
Low soil nitrogen (N) limits maize production in Zambia. S1 selection was used to select for tolerance to low N among ninety-six maize landraces during 2004 - 2007 in Zambia. The landraces were evaluated under low N, drought and optimal conditions; and selfed in a nursery, under optimal conditions. Data on grain yield (GY), number of ears per plant, leaf senescence and anthesis-silking interval were used to calculate selection indices. Fourteen S1 lines, from each of the best four landraces under each environment and across all environments were evaluated under the three environments, and at the same time crossed to a tester. Twenty-two best S1 lines under each environment and across were identified and also their testcrosses were evaluation under the three environments. Significant GCA effects for GY under low soil N were found; suggesting that population improvement under soil N stress was effective. Heritability for GY under low soil N conditions was low (0.38) implying that selection based on GY was ineffective. The rG for GY under low soil N and optimal environments was moderate (0.458), suggesting that selection for GY in one environment was not as effective as in the other. Low soil N tolerant landraces were identified and should be used to breed for the low soil N conditions.
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