Secondary traits in parental inbreds and hybrids under stress and non-stress environments in tropical maize

Abstract

Secondary traits other than grain yield (GY) have been successfully used to enhance the rate of genetic improvement for maize ( Zea mays L.) populations under abiotic stresses. With increasing trend towards the development of hybrids in the tropics there is a need to understand the genetics of these traits in inbred–hybrid breeding systems. The objectives of this study were to estimate the general combining abilities for secondary traits and their relationship with GY in a group of tropical white inbred lines and their hybrids under stress and non-stress environments. Traits were measured in inbred lines and their hybrid combinations across stress and non-stress subtropical and tropical environments in México. Hybrids showed earlier flowering, taller plants, more ears per plant (EPP), higher shelling percentage, slower leaf senescence, and higher leaf chlorophyll content than inbreds under all environments. La Posta Sequı́a (LP)-derived inbreds in general had desirable GCA for traits such as anthesis–silking interval (ASI), EPP, and leaf senescence but were more susceptible to foliar diseases. Conventionally bred maize lines had better standability, stay green, and resistance to diseases. Higher GY in lines and hybrids was associated with shorter ASI, earlier flowering, increased plant and ear height, increased EPP, increased shelling percentage, delayed senescence, and greater leaf chlorophyll concentrations. Under stress vs. non-stress conditions, we observed a higher variability for ASI and EPP, a higher inbred–hybrid correlation, and significant correlations between these traits and GY. Inbreds from LP appear to have high frequency of favorable dominant alleles for ASI and EPP.