High-Resolution Melting-Based Marker Development for Wheat Leaf Rust Resistance Gene Lr34

Area of Science:

• Plant genetics
• Molecular biology
• Agricultural science

Background:

• Adult plant resistance (APR) is crucial for wheat breeding against rust diseases.
• The Lr34 gene provides broad-spectrum resistance to leaf rust (Puccinia triticina).
• Existing molecular markers for Lr34 are often costly or require complex post-PCR steps.

Purpose of the Study:

• To develop a novel, economical, and efficient high-resolution melting (HRM) assay for genotyping the Lr34 gene in wheat.
• To validate the HRM assay's accuracy and reproducibility using different wheat lines and cloned gene copies.
• To assess the practical applicability of the HRM assay in wheat breeding programs.

Main Methods:

• Development of an HRM assay targeting a 3-bp 'TTC' deletion in exon 11 of the Lr34 resistant allele.
• Testing the assay on susceptible (Thatcher) and resistant (Thatcher near-isogenic line RL6058) wheat lines.
• Validation using cloned Lr34 homoeologs and a LunaProbe assay.
• Comparison with a kompetitive allele-specific PCR (KASP) assay on breeding lines.

Main Results:

• The HRM assay successfully differentiated susceptible and resistant wheat lines based on distinct melting profiles.
• HRM analysis of cloned Lr34 homoeologs confirmed accurate genotyping.
• The HRM assay showed comparable results to the KASP assay in differentiating resistant and susceptible breeding lines.
• The assay demonstrated high reproducibility but could not detect heterozygotes.

Conclusions:

• The developed HRM assay is a reliable, cost-effective tool for genotyping the Lr34 gene in wheat.
• This assay can aid in accelerating wheat breeding for leaf rust resistance.
• Further refinement may be needed to enable heterozygote detection.