Selection of Bread Wheat for Low Grain Cadmium Concentration at the Seedling Stage Using Hydroponics versus Molecular Markers

The excessive accumulation of Cd in harvested crops grown on high-Cd soils has increased public concerns for food safety. Due to the high consumption of bread wheat (Triticum aestivum L.) per capita, high concentrations of Cd in wheat grain can significantly affect human health. Breeding is a promising way to reduce grain Cd concentration. However, a lack of efficient selection methods impedes breeding for low grain Cd concentration in bread wheat. In this study, a recombinant inbred population segregating for grain Cd concentration was used to assess the efficacy of two selection methods for decreasing grain Cd concentration in bread wheat: a hydroponic selection method used shoot Cd concentration in 2-wk-old seedlings growing in Cd-containing medium, and a marker-based selection method using markers linked to heavy metal transporting P1B-ATPase 3 (HMA3), the gene underlying Cdu1. Both methods effectively selected low-Cd lines. The HMA3-linked marker-based selection was superior to hydroponic selection in terms of both simplicity and response to selection. The HMA3-linked markers explained 20% of the phenotypic variation in grain Cd concentration with an additive effect of 0.014 mg kg−1. The hydroponic selection and marker-based selection may target two different and independent processes controlling grain Cd accumulation, and they had no effect on grain Zn and Fe concentrations. The ALMT1-UPS4 marker associated with Al tolerance was not associated with grain Cd concentration but increased grain Zn and Fe concentrations. The 193-bp allele of the Rht8-associated marker, GWM261, was associated with increased grain Cd concentration

Single Nucleotide Polymorphism–based Genetic Diversity in the Reference Set of Peanut (Arachis spp.) by Developing and Applying Cost-Effective Kompetitive Allele Specific Polymerase Chain Reaction Genotyping Assays

Kompetitive allele-specific polymerase chain reaction (KASP) assays have emerged as cost-effective marker assays especially for molecular breeding applications. Therefore, a set of 96 informative single nucleotide polymorphisms (SNPs) was used to develop KASP assays in groundnut or peanut (Arachis spp.). Developed assays were designated as groundnut KASP assay markers (GKAMs) and screened on 94 genotypes (validation set) that included parental lines of 27 mapping populations, seven synthetic autotetraploid and amphidiploid lines, and 19 wild species accessions. As a result, 90 GKAMs could be validated and 73 GKAMs showed polymorphism in the validation set. Validated GKAMs were screened on 280 diverse genotypes of the reference set for estimating diversity features and elucidating genetic relationships. Cluster analysis of marker allelic data grouped accessions according to their genome type, subspecies, and botanical variety. The subspecies Arachis hypogaea L. subsp. fastigiata Waldron and A. hypogaea subsp. hypogaea formed distinct cluster; however, some overlaps were found indicating their frequent intercrossing during the course of evolution. The wild species, having diploid genomes, were grouped into a single cluster. The average polymorphism information content value for polymorphic GKAMs was 0.32 in the validation set and 0.31 in the reference set. These validated and highly informative GKAMs may be useful for genetics and breeding applications in Arachis species