Heterosis for Photosynthetic and Agronomic Characters in F1 Maize Hybrids (Zea mays L.)

Abstract

This study was conducted to estimate heterosis for photosynthetic and agronomic characters at the vegetative growth stage (7 - 9 leaves), heading stage and milk ripen stage in 3 F₁ maize hybrids and their parental cultivars (TP02A1/PR1025, AV10/II14, TC297/VN2). It was found that all F1 hybrids showed positive heterosis for photosynthetic rate (CER) at all growth stages. Especially  at milk ripen stage, the heterosis value over best parent (Hb) and over mid-parent (Ht) was in a range of 11% - 31% and  17% - 43%, respectively.

Photosynthetic rate was significantly correlated with SPAD value (an indicator of leaf chlorophyll content) at all growth stages, but not correlated with SLA (a revert indicator of leaf thickness). The growth duration of all F1 hybrids was shorter than that of their respective parents. A positive heterosis for leaf area index (LAI) and for dry matter accumulation was observed in all F1 hybrids at all growth stages. Grain yield was positively correlated with CER at heading stage. All F1 hybrid  showed positive heterosis for grain yield over the best parent (Hb = 174% - 267%) and over the mid -parent (Ht = 327% - 405%). Heterosis for grain yield was mainly contributed by the larger number of ears per plant.