Estimating parent-specific QTL effects through cumulating linked identity-by-state SNP effects in multiparental...

Area of Science:

• Plant genetics and genomics
• Quantitative trait loci (QTL) mapping
• Statistical genetics

Background:

• Multiparental mapping populations offer advanced insights into the genetic architecture of agronomic traits.
• A key question is whether to model genotype data as identical by state (IBS) or identical by descent (IBD).
• IBS uses raw genotype scores, while IBD is derived from parental offspring information.

Purpose of the Study:

• To compare the performance of IBS and IBD genotype modeling approaches for QTL mapping.
• To develop and validate a novel method for estimating multiallelic QTL effects using IBS data.
• To assess the applicability of the developed method in different multiparental populations.

Main Methods:

• Applied two multiple regression models to analyze four traits in the barley Nested Association Mapping (NAM) population HEB-25.
• Compared QTL mapping results and prediction abilities between IBS and IBD genotype models.
• Developed a 'cumulation method' to estimate parent-specific QTL effects from IBS data and validated it with simulations and a MAGIC population.

Main Results:

• Modeling parent-specific IBD genotypes yielded fewer significant QTLs but increased prediction abilities compared to IBS.
• At lower trait heritabilities, the IBS model demonstrated higher prediction abilities.
• The developed 'cumulation method' showed high accordance with IBD approaches for estimating parent-specific QTL effects and is applicable to MAGIC populations.

Conclusions:

• The choice between IBS and IBD modeling impacts QTL detection and prediction accuracy, with context-dependent advantages.
• The novel 'cumulation method' provides a universal approach to differentiate parent-specific QTL effects using IBS data, even without IBD information.
• This method enhances QTL analysis in multiparental populations and can be further improved with denser SNP maps.