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34 págs., 5 tabl. The definitive version is available at: https://www.crops.org/publications/cs, Maize (Zea mays L.) for northern growing areas requires cold tolerance for extending the vegetative period. Our objectives were to evaluate two large panels of maize inbred lines adapted to Europe for cold tolerance and to estimate the effects of cold-related traits on biomass production. Two inbred panels were evaluated for cold tolerance per se and in testcrosses under cold and control conditions in a growth chamber and under field conditions. Comparisons of inbreds and groups of inbreds were made taking into account the single nucleotide polymorphisms (SNP)-based genetic structure of the panels, and the factors affecting biomass production were studied. Eight flint and one dent inbred with diverse origins were the most cold tolerant. The most cold-tolerant dent and flint groups were the Iodent Ph207 and the Northern Flint D171 groups, respectively. The relationships between inbred per se and testcross performance and between controlled and field conditions were low. Regressions with dry matter yield in the field as dependent variable identified plant height (R2 = 0.285) as the main independent variable, followed by quantum efficiency of photosystem II (R2 = 0.034) and other traits with minor contributions. Cold-tolerance–related traits had low and negative effects on dry matter yield. Models intending the prediction of final performance from traits scored in early developmental stages are not expected to be precise enough for breeding. For improving cold tolerance, inbreds released from crosses among the No Iodent group and the Northern Flint group may show high combining ability, as well as between both groups and the Northern Flint D171 group., This research was supported in the framework of the Plant-KBBE program (project acronym “Cornfed”) by the Spanish Ministry of Science and Innovation (proj. EUI2008-03642 and EUI2008-03635), the French National Agency for Research (ANR, Ministry of High Education and Research), and the German Federal Ministry of Education and Research (grant numbers 0315461AD).

QTL for cell wall digestibility related traits were investigated in maize (Zea mays L.) topcross experiments of 240 RILs obtained from the F838 × F286 early maize hybrid. Genotype effects were highly signifi cant for all agronomic and cell wall related traits and much higher than genotype × environment (GE) interaction effects for cell wall digestibility traits. Eight quantitative trait loci (QTL) for dry matter (DM) yield were observed, out of which only one increasing allele originated from F286. Conversely, three QTL out of four with alleles increasing DM content at silage harvest stage originated from the earliest F286 line. Out of four QTL increasing starch content, two QTL, which originated from F838, did not colocalize with silking date QTL or any other investigated traits. Ten QTL were observed for lignin content and between six and nine QTL were observed for each of the three cell wall digestibility investigated traits. QTL located in bins 1.02 (position 76–80 cM), 1.07 (position 228–230 cM), and 8.07 (position 134–142 cM) are likely of priority interest when it comes to improving maize cell wall digestibility. Candidate genes underlying cell wall digestibility QTL were searched for on the basis of in silico investigations and with maize, Arabidopsis, poplar, and eucalyptus genomic information. In most of QTL positions, transcription factors regulating cell wall lignifi cation were shown to be the currently most plausible candidates involved in genetic variation of maize cell wall digestibility.