Generation mean analysis of leaf chlorophyll concentration from mid-silking to physiological maturity in some tropical maize (Zea mays L.) genotypes under low and high nitrogen dosages

Genetic control of the leaf chlorophyll concentration (LCC) in tropical maize (Zea mays L.) genotypes has not been established, especially at different reproduction growth stages under low and high nitrogen (N). A generation mean analysis study was conducted to identify the genetic effects that govern the LCC from mid-silking to physiological maturity under high (120?kg?N?ha^?1) and low (60?kg?N?ha^?1) (N) regimes for two seasons in a randomized complete block design with two replications during main and offseason of year 2009 at Inyala Agricultural Training Institute in Mbeya, Tanzania. This study revealed that mid-parent heterosis for the LCC increased with growth stages under both N dosages but it was more pronounced under low N dosage. Generally, genetic effects for LCC were more easily estimable under high than under low N dosage. Additive gene effects decreased with growth stage, whereas dominance effects increased, irrespective of the genotype and N regime. All genetic effects except dominance?×?dominance interaction were significant at some stages only in cross T20?×?N_G8. The ratio of fixable (additive plus additive?×?additive) to the non-fixable (dominance plus additive?×?dominance, and dominance?×?dominance) genetic effects was 74?C26?% under high N dosage, and 35?C65?% under the low N dosage for the T20?×?C58, while for the T20?×?N_G8, the ratio was 37?C63?% under high N dosage, and 20?C80?% under the low N dosage. The trend observed suggest that fixable effects are preponderant under the high N dosage in one cross, while non-fixable effects prevailed under the low N dosage in the other cross.