High-density genotyping: an overkill for QTL mapping? Lessons learned from a case study in maize and simulations

Area of Science:

• Plant Genetics
• Quantitative Genetics
• Maize Breeding

Background:

• High-density genotyping is common in genome-wide association studies and genomic selection.
• Linkage mapping studies in maize have traditionally used low-density genetic maps.

Purpose of the Study:

• To investigate if increased marker density benefits quantitative trait loci (QTL) mapping in biparental maize populations.
• To evaluate the impact of marker density on QTL mapping parameters.

Main Methods:

• Utilized experimental data from a biparental population of 204 doubled haploid maize lines.
• Conducted simulation studies with varying QTL effects and population sizes.
• Performed QTL mapping using genetic maps with marker densities of 1, 2, and 5 centimorgans (cM).

Main Results:

• High-density maps did not enhance QTL detection or predictive power for explained genotypic variance.
• Increased marker density significantly improved the precision of QTL localization and effect estimates, particularly for small to medium QTL.
• Higher marker density enhanced the ability to resolve closely linked QTL.

Conclusions:

• Increased marker density in linkage mapping provides more precise estimates for knowledge-based breeding in maize.
• The benefits of higher precision in QTL parameters justify the increased costs associated with high-density genotyping for linkage mapping.