Novel Genomic Regions and Gene Models Controlling Copper and Cadmium Stress Tolerance in Wheat Seedlings

Heavy metal pollution is a global issue that affects plant growth and human health. Copper and cadmium are two significant heavy metals that have become more concentrated in many soils. These metals are taken up by many plants, including wheat, and can cause various diseases in humans. The most effective way to mitigate the harmful effects of heavy metals is to grow tolerant wheat genotypes. In the current study, two different pot experiments were conducted to understand the genetic control of copper and cadmium tolerance in wheat seedlings. Two populations were used in this study, consisting of 92 genotypes for the copper experiment and 73 genotypes for the cadmium experiment. In both experiments, a replicated complete block design with three replications was used. Highly significant differences were found between the tested genotypes for all studied traits in both metals, except for root weight and the ratio between shoot weight and root weight under cadmium contamination. Single-marker analysis was performed for all significant traits, and a total of 265 and 381 markers were found to be significantly associated with seedling traits under copper and cadmium conditions, respectively. Of these markers, only eight were commonly associated with the tolerance to both metals. These markers were located within five different gene models that were functionally annotated to control heavy metal tolerance. Gene enrichment of the five identified genes revealed two key genes that significantly influenced eight biological processes, six molecular functions, and three Kyoto Ecyclopedia of Genes and Genomes (KEGG) pathways involved in heavy metal tolerance. The sources of the eight markers and their associated genes were identified in twelve genotypes, including one Egyptian and one Kazakhstani genotype, which showed superior responses to copper and cadmium, respectively. These genes and the genotypes carrying them are crucial for future breeding programs aimed at enhancing heavy metal tolerance in wheat.