Genetic variation for lignin content and cell wall digestibility in early maize lines derived from ancient landraces

International audience; Remarkable genetic improvement in maize yield, lodging resistance, biotic and abiotic stress tolerance were obtained during the 1955 - 2000 period in Europe. However, a decline in the average cell wall digestibility of maize hybrids has been observed during the 1980 - 2000 period. This trend has now ceased with the breeding of specialized silage varieties. The cell wall degradability of the best current hybrids does not yet equal that of better old types of the 1960s era such as INRA258, mostly because the germplasm currently used in maize breeding corresponds to progenies of resources initially chosen for grain maize breeding. Nearly 110 new lines were thus derived by self-pollination in old or unused landraces and accessions in order to test the interest of this kind of genetic resources in maize breeding for cell wall degradability traits. Based on per se and topcross experiments, several lines representative of different and new germplasm displayed high or medium high cell wall digestibility. F7103 (Argentina-BBC143), F7104 (Argentina-BBC325), F7106 (Gelderland-VC150), F7114 (Zakarpatskaja-Zeltaja-Zubovidnaja), and F7121 (Comptons-Early) are likely among the more romising new resource lines for improvement of cell wall digestibility in elite dent or flint germplasm. These lines covered a large genetic diversity as F7103 and F7104 are mostly lowland tropical, F7106 and F7121 mostly northern flint, F7114 mostly Oh43/Minnesota13 related. Two other lines of medium-high cell wall digestibility, F7101 (St Engrace) and F7112 (Mecklenburger), were shown to be significantly related to lowland tropical germplasm. Several landraces or old varieties also gave lines of low cell wall digestibility such as F7124 (Curaco-de-Velez) or F7126 (Baanbreker), both related to the northern flint group. Average yield of top-crossed lines was nearly 7 t/ha lower than the average value of the three control hybrids and only one hybrid (F7104 x UH002) had yield and earliness equal to those of control hybrids. These low values were related to the fact that investigated lines were derived from old resources that did not get the last 60 years genetic improvements, and also to the only use of a flint male for top-crosses that did not optimize the genetic distance with all top-crossed lines. Allele sequencing and association genetics should give markers for targeted introgression of new alleles of interest originating from this specific set of lines in elite lines.