Maize (Zea mays L.) is one of the most crucial crops for global food security worldwide. For this reason, many efforts have been undertaken to address the efficient utilization of germplasm collections. In this study, 322 inbred lines were used to link genotypic variations (53,403 haplotype blocks (HBs) and 290,973 single nucleotide polymorphisms (SNPs)) to corresponding differences in flowering-related traits in two locations in Southern Brazil. Additionally, network-assisted gene prioritization (NAGP) was applied in order to better understand the genetic basis of flowering-related traits in tropical maize. According to the results, the linkage disequilibrium (LD) decayed rapidly within 3 kb, with a cut-off value of r2 = 0.11. Total values of 45 and 44 marker-trait associations (SNPs and HBs, respectively) were identified. Another important finding was the identification of HBs, explaining more than 10% of the total variation. NAGP identified 44, 22, and 34 genes that are related to female/male flowering time and anthesis-silking interval, respectively. The co-functional network approach identified four genes directly related to female flowering time (p < 0.0001): GRMZM2G013398, GRMZM2G021614, GRMZM2G152689, and GRMZM2G117057. NAGP provided new insights into the genetic architecture and mechanisms underlying flowering-related traits in tropical maize.

The variance analysis showed significant effects (p < 0.05) of inoculation (Londrina environment) and N rates (both environments) only for grain yield. There was no inoculation effect in the grain yield when inoculants were applied together with N-fertilization at topdressing. In the absence of N-fertilization at topdressing, the inoculants Masterfix L. and UEL promoted higher grain yield as compared to the uninoculated plants, with resulting increases of 13.21 and 26.61% in yield, respectively.

This study aimed to evaluate the inbreeding depression and average genetic components in seven hybrids and two open pollinated cultivars for green corn production, as well as to select the best genotypes in order to obtain base populations for inbred lines extraction. The experiment was carried out in a randomized complete block design with four replications, in a split plot design, with inbreeding levels arranged in the plots and the different genotypes distributed over the subplots, in the municipality of Sabáudia - PR, during the 2014/15 crop season. Higher values of dominance and inbreeding depression were observed for yield of both unhusked and commercial ears. Higher additive effects were detected on length and diameter of commercial ears. The genotypes AM811, Cativerde 02 and AG4051 showed greater probability of obtaining highly productive and higher quality green corn inbred lines.

The fungus Aspergillus flavus can produce high, unsafe levels of aflatoxin in maize (Zea mays L.) and other high-oil seed crops under environmental conditions favoring fungal growth and sporulation. At high levels, aflatoxin can kill, and chronic exposure to lower levels causes liver cancer, stunted growth during childhood, and depressed immune systems in humans and animals. Aspergillus ear rot (AER) is especially problematic in tropical environments, but most gene identification studies have been done in temperate or subtropical maize. Thus, the objectives of this research include identifying and mapping chromosomal regions and genes associated with AER resistance in tropical maize inbred lines via genome-wide association study (GWAS) and tying these genes to metabolic pathways and potential resistance mechanisms. A panel of 320 tropical field corn and popcorn inbred lines was analyzed with phenotypic data for AER collected in two environments after harvest, and a set of 291,633 high-quality polymorphic single-nucleotide polymorphisms (SNPs) generated via genotyping by sequencing. Seven SNPs significantly associated with AER were identified. Pathway analysis identified 56 associated pathways, yielding possible resistance mechanisms related to flavonoid and phytoalexin plant compounds, plant signaling via hormones, starch biosynthesis, and general plant growth and metabolism. Many of the same genes were identified by both analyses, but GWAS and pathway analysis jointly identified more candidate genes than either alone.

Fusarium ear rot (FER), caused by Fusarium verticillioides (Sacc.) Nirenberg, is one of the major ear diseases that affect both yield and grain quality in maize (Zea mays L.), especially in tropical environments. Fusarium genetic resistance is a complex trait, controlled by several small‐effect genes and strongly influenced by the environment. We applied a comprehensive genome‐wide association study and genomic prediction for ear rot and starburst symptoms, using 291,633 high‐quality single nucleotide polymorphism (SNPs) markers in 320 tropical maize inbred lines, in two distinct locations in Brazil's southern region. Three SNPs were significantly associated with starburst symptoms, each associated with 6–8% of the phenotypic variance, and with gene models that have expression levels in ears, pericarp, and kernels, corresponding to disease infection period and suggesting some role in FER resistance. No significant SNP was associated with FER, which is an indication that the genetic architecture for this trait is highly polygenic, with potentially many variants having small effects that are not detectable in the association mapping analysis. We observed genomic prediction accuracies ranging from 0.34 to 0.4 for FER and starburst, respectively. Further research is required to validate these significant SNPs and their relationship to genes affecting FER resistance, and also to improve genomic prediction accuracies across different genetic backgrounds.