Genetic variation in maize cell wall for lignin content, lignin structure, p-hydroxycinnamic acid content, and digestibility in set of 19 lines at silage harvest maturity

Abstract

Genetic variation for carbohydrate content, lignin content, lignin composition, p-hydroxycinnamic acid content and digestibility were investigated in a set of 19 maize lines over a two year period (2002 and 2003) and in two locations (Lusignan and Druelle, France). The studied set was comprised of old and recent elite lines representative of cell wall digestibility variations and sev- eral model lines involved in digestibility and intake breeding schemes. A large degree of genetic variation for cell wall composition and digestibility was observed. Lignin content appeared to be the primary determinant in cell wall digestibility variation (r 2 = 0.77). H and S monomeric unit contents also appeared to be negatively correlated with digestibility. The cell wall cross-linkages with ferulic and diferulic acids were significantly correlat- ed with digestibility, but with two apparently contrary ef- fects. A negative correlation was found between etherified ferulic acid content and cell wall digestibility while a pos- itive one was found between diferulic acid content and digestibility. These results strengthened the ambiguity concerning the real proportion of ferulic and diferulic acids measured after an alkaline hydrolysis. A negative correlation was found between p-coumarate content and digestibility. This result confirmed the efficiency of these acids as an estimator of feeding value. Finally, a positive correlation between hemicellulose content and digestibili- ty showed that cell wall carbohydrate composition could impact cell wall digestibility. A new ideotype of forage maize can be designed based on the cell wall correlations highlighted in this study, but an elite line improved for feeding value traits (and biofuel production) have to take simultaneously into agronomic traits. Such an ideotype will therefore be used by maize breeders as an allele donor in marker assisted breeding programs.