QTL mapping of biomechanical traits related to lodging resistance in bread wheat

Lodging is the permanent horizontal growth of stem and has been considered as a limiting factor in cereal production. Identification of traits that affect grain yield is very important in breeding programs. Furthermore, genetic diversity is essential for breeding programs and increasing selection efficiency. This research was set up to study genetic diversity, evaluation of biomechanical traits, assess lodging stem and detect quantitative traits loci (QTLs) in a RIL population of bread wheat. 

A large population including 225 bread wheat lines was assessed in a randomized complete block design with two replications in research field of Shahid Bahonar University of Kerman during 2017-2018 growing season. To define biomechanical properties of stems, a universal testing machine equipped with 3-point bend and shear test probes was used.   

Results of ANOVA showed significant difference between wheat genotypes for all traits. Modulus of elasticity of stem had the highest response to selection (21.65) in comparison with other traits. Moreover, this trait had high genetic variation. Based on these results, modulus of elasticity of each individual plant stem can be used as an effective factor in selection programs. Plant height had the highest narrow sense heritability (0.59) among evaluated traits. Cross section area had strong and significant correlation with moment of inertia (r=0.818**). In the molecular assay of this research, linkage map and QTL mapping of traits performed by inclusive composite interval mapping (ICIM) method. Linkage map was constructed based on diversity array technology (DArTs) and SSR markers. 

A total of 12 QTLs have been identified which had LOD higher than 2.5. These QTLs were controlling 6 biomechanical traits including: specific shear energy, maximum shear energy, moment of inertia, flexural stiffness, maximum specific bending strength and modulus of elasticity. The information of identified QTLs could be used in wheat breeding programs using marker assisted selection.