Heterosis of quality protein maize inbred lines for agronomic traits and association with genetic distances based on SSR and phenotypic markers

Due to high cost, limited labour, and longer time required in hybrid development, identifying promising hybrids at an early stage without large-scale yield trials is crucial. Therefore this study estimated heterosis of quality protein maize hybrids for grain yield (GY) and other agronomic traits and investigated relationship of genetic and phenotypic distances (GD, PD) of inbreds with hybrid performance (HP) and mid-and-better parent heterosis (MPH, BPH). Forty-five hybrids generated by half-diallel with 10 inbreds were evaluated for GY and other agronomic traits at three locations. The yield trials were conducted for two years (2017 and 2018 cropping seasons). The GD and PD were 0.45 and 0.40 based on SSR and phenotypic data, respectively, this shows moderate genetic variation existed among inbreds. GY had highest MPH (77.55%) and BPH (53.96%) with hybrid TZEEQI-9 × TZEEQI-16 having highest MPH (382.8%) and BPH (331.7%), across locations. Positive and significant association existed between SSR-GD with HP, MPH and BPH for ear length, kernels/row and 100-seed weight (r = 0.31** to 0.41**), this suggests these traits can be predicted from SSR-based GD of parents. These traits could be used for indirect selection for yield improvement. However, negative correlation was obtained between SSR-GD with HP, MPH and BPH for anthesis and silking (r = −0.29 to −0.03), this indicates the dominance for earliness to flowering and silking than their parental lines. The two distance measures can be used to differentiate between maize inbreds and assigned them to different heterotic groups and Breeders can therefore prioritize crosses with high heterosis and desirable phenotypic traits, saving time, resources, and field space.