Drought is one of the most detrimental abiotic stresses hampering seed germination, development, and productivity. Maize is more sensitive to drought than other cereals, especially at seedling stage. Our objective was to study genetic regulation of drought tolerance at germination and during seedling growth in maize. We evaluated 420 RIL with their parents from a multi-parent advanced generation inter-cross (MAGIC) population with PEG-induced drought at germination and seedling establishment. A genome-wide association study (GWAS) was carried out to identify genomic regions associated with drought tolerance. GWAS identified 28 and 16 SNPs significantly associated with germination and seedling traits under stress and well-watered conditions, respectively. Among the SNPs detected, two SNPs had significant associations with several traits with high positive correlations, suggesting a pleiotropic genetic control. Other SNPs were located in regions that harbored major QTLs in previous studies, and co-located with QTLs for cold tolerance previously published for this MAGIC population. The genomic regions comprised several candidate genes related to stresses and plant development. These included numerous drought-responsive genes and transcription factors implicated in germination, seedling traits, and drought tolerance. The current analyses provide information and tools for subsequent studies and breeding programs for improving drought tolerance.

Cultivated potato (Solanum tuberosum L.) is one of the most important crops worldwide. Phytophthora infestans (Mont.) de Bary is the oomycete pathogen responsible for the famous Irish famine (1840s). It is still the most important pathogen affecting potato crops, causing the late blight disease on potato and tomato. It is mainly controlled by fungicides. Breeding for disease resistance is the best alternative to chemical control of the disease. One of the strategies used is to stack many resistance genes in the same genotype. Here, we wanted to test the effect of the stacked resistance gene (R) from S. demissum on the infection process by the virulent race EU_13_A2. Four potato genotypes were tested, each one harboring, respectively, one, two, three or four R genes. All the tested genotypes were sensitive. However, the sensitivity degree was negatively correlated with the number of genes harbored by each genotype. There was a delay of two days of symptoms manifestation for the genotype with 4Rs, and the pathogen produced less spores on the detached leaf test. In addition, the amount of phenolic compounds produced is higher in the genotypes with multiple R genes.