Diallel Analysis of Photosynthetic Traits in Maize

Capability to intercept and utilize sunlight is important in maize (Zea mays L.) for its growth and dry matter accumulation. Little research has been conducted on the combining ability of maize physiological traits related to photosynthesis, such as light saturation point (LSP), light compensation point (LCP), apparent quantum efficiency (AQE), maximum photosynthesis (Pmax), total protein content (PRO), and activity of phosphoenolpyruvate carboxylase (PEPC) and ribulosebisphosphate carboxylase (RuBPC). The five photosynthesis-related traits and two key enzymes were examined for their combining abilities using a six-parent diallel design. The objectives were to (i) evaluate general combining ability (GCA) and maternal (MAT) effects of the six maize lines and specific combining ability (SCA) and nonmaternal (NMAT) effects for crosses and (ii) determine if GCA effects were different among three maize heterotic groups. Results revealed that the additive gene effects were more important than nonadditive effects for LSP, LCP, Pmax, PRO, PEPC, and RuBPC. Maternal effects for LCP, PRO, and RuBPC were significant and positive for some lines, which could be used as female parents in hybrid development. Information on means of parental lines, combining ability, and heterosis values suggested that RUBPC, PEPC, and PRO might be the key traits that make the Suwan 1 heterotic group different from the Reid and non-Reid groups and should be explored fully in future hybrid maize breeding programs.