Major genetic changes in wheat with potential to affect disease tolerance

Area of Science:

• Plant genetics and breeding
• Crop pathology
• Agronomy

Background:

• Most UK winter wheat possesses Rht-D1b semi-dwarfing allele, 1BL.1RS translocation, and suppressed awns due to breeding.
• These genetic changes are widespread in elite germplasm.
• Their impact on disease tolerance is largely uncharacterized.

Purpose of the Study:

• To investigate the effect of major genetic changes in winter wheat on disease tolerance.
• To quantify tolerance to Septoria leaf blotch and stripe rust in near-isogenic lines (NILs).

Main Methods:

• Utilized NILs differing in specific genetic traits (Rht-D1b, 1BL.1RS, awns).
• Assessed tolerance to Septoria leaf blotch and stripe rust across four field experiments over two seasons.
• Quantified tolerance as yield loss per unit of green canopy area lost to disease.

Main Results:

• A trend for the 1BL.1RS translocation to decrease tolerance was observed, though not consistently.
• The presence of awns decreased tolerance compared to unawned NILs.
• Significant differences in tolerance were found between cultivar backgrounds, with modern lines showing lower tolerance.

Conclusions:

• The 1BL.1RS translocation and awns may negatively impact winter wheat disease tolerance.
• Breeding for specific traits has led to varied tolerance levels in different genetic backgrounds.
• Physiological traits like flag leaf area, potential yield, carbohydrate reserves, and grain sink capacity correlate with tolerance differences.