Secondary traits related to kernel setting in transgenic maize hybrids at low and high plant densities and their potential use in breeding programs

Maize (Zea mays. L) traditional breeding presents limitations when selection is performed by adaptation to suboptimalconditions. One strategy to achieve greater efficiency in these environments is to include measurements ofsecondary traits related to the main grain yield component, i.e. kernel number per plant (KNP), which is associatedto other three secondary traits: plant growth rate during the critical period (PGRcp) for kernel setting, biomasspartitioning index to the ear during this period (PIcp) and the efficiency of the ear to set kernels or reproductiveefficiency (RE). Phenotypic variations in these KNP related traits were evaluated considering: i) plant densities,and ii) simple and staked transgenic maize hybrids. The objective of this study was to identify the contribution ofthese secondary traits to KNP in six modern single-cross transgenic hybrids: the simple and staked transgenic versionsof DK747 and DK190 (Bt: 747MG and 190MG; RR: 747RR and 190RR; and Bt-RR: 747MGRR and 190MGRR)cultivated at low and high plant densities. For this purpose, KNP and secondary traits were recorded at the individualplant level and the data set was analyzed using multivariate analysis techniques. At low plant density, PGRcpwas the critical trait for kernel setting in all hybrids but PIcp or RE also contributed to KNP of the DK747 groupand the D190 group, respectively. At high plant density, a differential contribution of secondary traits to KNP wasrecorded among hybrids. For DK747MG and DK190MG, RE mainly determined KNP, but for the DK747RR andDK747MGRR higher PIcp had a positive impact on KNP. These results highlight the importance of including secondarytraits associated to KNP in breeding programs