Mean Performance, Heterobeltiosis and Combining Ability of Corn (Zea mays L.) Agronomic and Yield Traits under Elevated Plant Density

The objective of this study was to assess performance, heterosis and combining ability parameters and their interrelationships in six maize inbreds and their 15 diallel F1 crosses under different plant densities (D). Three experiments were carried out in each season of 2013 and 2014, using RCBD with three replicates. The experiment consisted of three treatments, i.e. low-D, medium-D or high-D (47,600, 71,400 and 95,200 plants/ha, respectively). A greater portion of additive than non-additive variance across seasons was observed for leaf angle (LANG), ears/plant (EPP), Kernels/row (KPP) and rows/ear (RPE) under all environments. Similar results were observed for 100-kernel weight (100 KW) under low and high plant densities, and barren stalks (BS) and days to anthesis (DTA) under low plant density. The rest of traits exhibited greater preponderance of non-additive variance. For grain yield/plant (GYPP), the best inbred in general combining ability (GCA) effects was L53 followed by L20 and Sk5 and the best cross for specific combining ability (SCA) effects was Sk5 × L18 followed by L20 × L53 and L28 × Sd7 under the three environments. Out of 12 traits, the highest performing inbred lines were those that displayed the highest GCA and vice versa for nine traits and the highest performing crosses were the highest specific combiners and vice versa for all 12 traits under all plant densities. For anthesis silking interval (ASI), plant height (PH), ear height (EH) and BS under all environments, DTA and LANG (except low-D) and EPP under low-D, the mean performance of a cross could be used as an indicator of its useful heterosis. For LANG, EPP, RPE, kernels/row (KPR), KPP, 100 KW (except high-D), BS (except low-D) and ASI (except medium-D), the useful heterosis of a cross could be used as an indicator of its SCA effects under the corresponding environments.