Genetic variation for cell wall degradability in maize inbred lines without and after alkaline pretreatments

Alkali pretreatments were applied at two temperatures on a set of eight maize lines exhibiting a large range of cell wall degradability, which was comprised between 49.4 and 24.9%. The effect of NaOH concentration on cell wall degradation was shown strongly preponderant over the effect of temperature, with significant interactions be- tween alkali concentrations and temperatures. Interactions between lines and NaOH concentration or temperature were weak or non significant. With mild-alkaline 0.02 N pretreatment, cell wall degradation was similarly increased by 36% for all considered lines, without any difference between 22°C or 50°C temperature conditions. With more severe 0.2 N alkaline pretreatment, average cell wall degradation was increased by 114% and 140% at 22°C and 50°C, respectively, leading also to a reduced range of variation between lines, especially at the highest tempera- ture. However, whatever pretreatment conditions, the line effect stayed highly significant, even when it was greatly reduced. With a solution of 0.2 N NaOH at 22°C, nearly 80% and 70% of cell walls were solubilized in more and less degradable lines, respectively. Such pretreatment conditions limit both energy costs and amounts of effluents to be recycled. Breeding maize lines and hybrids for higher degradability of their cell walls is thus a relevant goal for both animal feeding and environmentally friendly production of bioenergy.