Genetic analysis and QTL mapping of cell wall digestibility and lignification in silage maize

Improving digestibility is a major goal for forage maize (Zea mays L.) bree ding programs. Quantitative trait loci (QTL) affecting forage maize digesti bility-related and agronomic traits were mapped and characterized in a set of recombinant inbred lines (RIL). Eleven traits were analyzed on whole pla nt samples: neutral detergent fiber (NDF), starch content (STC), crude prot ein content (CPC), acid detergent lignin (ADL), in vitro dry matter digesti bility (IVDMD), in vitro cell wall digestibility (IVNDFD), in vitro digesti bility of non-starch and non-soluble carbohydrate (IVDNSC), dry matter cont ent (I)MC), dry matter yield (I)MY), mid-silk date (SILK), and plant height (PHT). Evaluation was performed among the RIL populations studied per se ( RILps) and in combination with a tester (TC). The genetic variances (sigma (2)(g)) were highly significant and, in most cases, greater than genotype X year interaction variances (sigma (2)(gxy)). Heritabilities ranged from 0. 49 to 0.70 in RILps and from 0.12 to 0.58 in TC. Twenty-eight QTL were iden tified among TC by CIM, which explained individually between 3.3 and 20.2% of the phenotypic variation (R-p(2)) for traits related to digestibility or agronomic performance. Twenty QTL were identified among RILps, which expla ined individually between 6.5 and 15.3% of the phenotypic variation (M). Se ven of these QTL were common to TC and RILps. Cell wall digestibility estim ates (IVNDFD or IVDNSC) were the traits with the highest number of QTL. In contrast, we detected only one QTL for dry matter digestibility (IVDMD). Th us, it may be useful to separate IVDMD into its two component parts, cell w all digestibility, which could be estimated from line per se values, and st arch content. Characteristics such as IVDNSC or IVNDFD, coupled with QTL in formation, would be powerful tools in the search for genes involved in maiz e lignification or cell wall biogenesis.