Variability and Associations of Grain Filling Traits with Grain Yield and Yield Components in CIMMYT Maize Inbred Lines

Improved grain filling rate and grain filling duration are yield components that have potential to increase maize yield in early maize germplasm. These two factors have not been well studied in maize and thus cannot be easily exploited in improving maize yield. This study was therefore carried out to determine genetic variability of grain filling rate and grain filling duration and their associations with yield and yield components in early maize germplasm. Maize was planted early and late. Maize cobs were harvested weekly from a single plant per plot starting two weeks after pollination, and a sample of grains dried to constant weight and weighed. A log linear equation was fitted on the percentage dry matter content per sample per week and used to predict the lag phase duration (LPD), the linear phase duration (also called the effective grain filling duration) (EGFD) and the final phase duration (FPD). Across environments analyses of variance showed significant differences (P<0.001), high broad sense heritability, low error and G x E variance component but high genotype variance component for all traits recorded such as GY, GFR and EGFD except LA. There were significant differences between the mean of the high yielding group and the lower yielding group. The high yielding group flowered (both anthesis and silking) earlier. GY was positively correlated with 1000 kernel weight (r=0.67), GFR (r=0.61), EGFD (r=0.47) and TGFD (r=0.52) as well as ASI (r=0.26). However, GFR and EGFD were negatively correlated (r= - 0.40. Therefore, selection for longer TGFP, high GFR and shorter ASI without extending DPM can improve the yield of early maize.