The improvement of maize double cropping has become increasingly important in recent years. In order to establish breeding programs for sustainable maize production, the goals of the research were (i) to understand the correlations between grain and stover yield and saccharification efficiency, and (ii) to identify QTL and metabolic pathways to design of breeding programs in a double exploitation approach. We carried out a genome-wide association study (GWAS) and a metabolic pathway analysis using a panel of highly diverse maize inbreds. As results, we have obtained that the regulation of energetic and developmental pathways have been pointed out as key pathways related to stover quantity and utilization, while no specific pathways could be identified in relation to grain yield. However, due to the moderate high heritability of yields and their positive correlation a phenotypic selection approach would be adequate for the improvement of both yields, while for saccharification efficiency improvement upcoming genomic selection models are more advisable. Overall, breeding strategies that manage the dual use of maize are viable and will contribute to a more sustainable maize crop in the near future.

Maize kernel is exposed to several fungal species, most notably Fusarium verticillioides, which can contaminate maize kernels with fumonisins. In an effort to increase genetic gains and avoid the laborious tasks of conventional breeding, the use of marker-assisted selection or genomic selection programs was proposed. To this end, in the present study a Genome Wide Association Study (GWAS) was performed on 339 RILs of a Multiparental Advanced Generation InterCross (MAGIC) population that had previously been used to locate Quantitative Trait Locus (QTL) for resistance to Fusarium Ear Rot (FER). Six QTLs for fumonisin content were detected in the bins 3.08, 4.07, 4.10, 7.03-7.04, 9.04-9.05 and 10.04-10.5. Five of the six QTLs collocate in regions where QTLs for FER were also found. However, the genetic variation for fumonisin content in kernel is conditioned by many other QTLs of small effect that could show QTL x environment interaction effects. Although a genomic selection approach to directly reduce fumonisin content in the kernel could be suitable, improving resistance to fumonisin content by genomic selection for FER would be more advisable.

Hydroxycinnamates, like ferulate (FA) and p-coumarate (pCA), are important components of maize cell walls, which influence pest resistance, ruminal digestibility, and biofuel production. Increasing their concentration has been linked to increased pest resistance, but also may lead to a decrease in nutritional value or bioethanol production efficiency. Therefore, improving forage quality or biofuel production without compromising plant resistance and a thorough understanding of the biosynthesis and deposition of these compounds is necessary, especially in stover, which is the feedstock for second-generation biofuel production and determines animal forage quality. This study aimed to identify genomic regions associated with hydroxycinnamates and to develop genomic prediction models to determine the best selection approach to modify hydroxycinnamate content. Although heritability estimates for hydroxycinnamates were moderate, direct phenotypic selection is discouraged because hydroxycinnamate quantification is laborious and time-consuming. Negative genotypic correlations were observed between animal digestibility and pCA content and positive with diferulates content, suggesting differing effects compared to previous studies on maize pith. However, no colocalizations with digestibility QTLs were found, highlighting the need for further research. Given the moderate predictive capacity of GBLUP prediction models, genotypic selection is proposed as the most promising alternative for modifying hydroxycinnamate content.

Maize resistance to borers and fungi is associated with structural strengthening of the cell wall, though the roles of constitutive, induced, and priming-modulated defenses are not fully understood. Additionally, this study examined how seed inoculation with the endophytic/pathogenic fungus Fusarium verticillioides affects maize cell wall responses against Sesamia nonagrioides infestation. Seven maize inbred lines were evaluated under four treatments combining fungal seed inoculation and insect infestation. Insect damage, lignin composition and cell wall–bound hydroxycinnamates, were quantified in stem pith tissue.,Treatments significantly altered lignin composition and ferulic acid and diferulate accumulation, while total lignin content and p-coumaric acid levels remained unchanged. Without Fusarium, Sesamia infestation reduced syringyl (S) lignin and decreased ferulic acid and diferulates. In contrast, Fusarium inoculation modified basal diferulate levels and reprogrammed maize metabolic responses, inducing ferulic acid and diferulates and shifting lignin composition, including reduced S and S/G ratio and increased guaiacyl (G) subunits. Responses were strongly genotype-dependent.,Overall, maize resistance to S. nonagrioides depends on the integration of constitutive defenses, inducible cell wall remodeling, and priming effects, highlighting the adaptive value of cell wall metabolic plasticity under multiple biotic stresses.

Leaves are a primary organ of interest for studying drought tolerance in maize because they integrate the main physiological and biochemical responses that determine carbon gain, water loss, and growth under water deficit. However, the association of elemental traits and cell wall-bound phenolics in leaves under drought conditions in real field conditions remains poorly understood. We evaluated 15 diverse Mediterranean maize inbred lines over two years under well-watered and water-deficient field conditions. Drought stress significantly reduced plant height and biomass yield, decreased leaf nitrogen concentration and δ15N, and increased the C ratio. At the cell wall level, water deficit increased p-coumaric acid, ferulic acid, and diferulates, while lignin content remained unchanged. Attending to the differential response of inbreds evaluated, drought-sensitive lines showed larger increases in hydroxycinnamates and diferulate cross-linking, together with greater reductions in nitrogen. In contrast, tolerant lines-maintained biomass with smaller declines in nitrogen and more limited wall dimerization. These findings suggest that increased wall fortification reflects a defensive, growth-limiting response, rather than an advance under drought conditions. Nitrogen homeostasis and restrained cell wall cross-linking emerge as distinctive traits of drought-resilient genotypes.