Genetic Characterization of a Wheat Association Mapping Panel Relevant to Brazilian Breeding Using a High-Density Single Nucleotide Polymorphism Array.

Bread wheat (Triticum aestivum L.) is one of the world's most important crops. Maintaining wheat yield gains across all of its major production areas is a key target toward underpinning global food security. Brazil is a major wheat producer in South America, generating grain yields of around 6.8 million tons per year. Here, we establish and genotype a wheat association mapping resource relevant to contemporary Brazilian wheat breeding programs. The panel of 558 wheat accessions was genotyped using an Illumina iSelect 90,000 single nucleotide polymorphism array. Following quality control, the final data matrix consisted of 470 accessions and 22,475 polymorphic genetic markers (minor allele frequency ≥5%, missing data <5%). Principal component analysis identified distinct differences between materials bred predominantly for the northern Cerrado region, compared to those bred for southern Brazilian agricultural areas. We augmented the genotypic data with 26 functional Kompetitive Allele-Specific PCR (KASP) markers to identify the allelic combinations at genes with previously known effects on agronomically important traits in the panel. This highlighted breeding targets for immediate consideration - notably, increased Fusarium head blight resistance via the Fhb1 locus. To demonstrate the panel's likely future utility, genome-wide association scans for several phenotypic traits were undertaken. Significant (Bonferroni corrected P < 0.05) marker-trait associations were detected for Fusarium kernel damage (a proxy for type 2 Fusarium resistance), identifying previously known quantitative trait loci in the panel. This association mapping panel represents an important resource for Brazilian wheat breeding, allowing future genetic studies to analyze multiple agronomic traits within a single genetically diverse population.

Alleles of organic acid transporter genes are highly correlated with wheat resistance to acidic soil in field conditions.

KEY MESSAGE: TaALMT1 and TaMATE1B promoter alleles are highly correlated with wheat growth in acidic soil with a high concentration of toxic aluminium. The aluminium (Al(3+)) resistance of 338 wheat genotypes with different geographic origins was correlated with morphological traits and TaALMT1 and TaMATE1B alleles. Both of these genes encode malate and citrate transporters associated with Al(3+) resistance mechanisms in wheat. Based on comparisons with the sensitive and resistant controls, the relative root growth was evaluated in hydroponic experiments and the plant performance was visually accessed in the field. The correlation between Al(3+) tolerance in the hydroponic and field tests was moderate (r = 0.56, P < 0.001). Higher selection pressure was observed in the field because a smaller number of genotypes was classified as resistant. The combination between the six TaALMT1 alleles and the two TaMATE1B promoters allowed the identification of 11 haplotypes that showed a high (r = 0.71, P < 0.001) correlation with Al(3+) resistance in the field, with the TaALMT1 alleles accounting for most of the correlation. The Brazilian wheat genotypes presented the best performance in soil, including eight cultivars with promoters usually associated with Al(3+) resistance and another six genotypes classified as moderately resistant but containing alleles usually associated with Al(3+) sensitivity. Although an increase in favourable alleles was observed over the past few decades, the average Al(3+) resistance in the field was not significantly different from that of older cultivars. The ease identification of the TaALMT1 and TaMATE1B alleles and their higher association with Al(3+) resistance along with the best genotypes identified here may be used for wheat-breeding programmes interested in increasing wheat Al(3+) resistance.