Exploring standing genetic variation for barley leaf rust resistance in Australian breeding panel

Area of Science:

• Plant genetics and breeding
• Agricultural science
• Crop pathology

Background:

• Barley leaf rust (BLR), caused by Puccinia hordei, poses a significant threat to global barley (Hordeum vulgare L.) production.
• Understanding resistance mechanisms across diverse environments is crucial for developing resilient cultivars.
• Limited research has explored genotype-by-environment interactions (GEI) for BLR resistance.

Purpose of the Study:

• To investigate GEI in barley leaf rust resistance using multi-environment trial (MET) data.
• To identify novel genomic regions (haplo-blocks) associated with stable BLR resistance.
• To explore the potential of haplotype stacking for enhancing adult plant resistance (APR).

Main Methods:

• Multi-environment trial (MET) analysis of BLR disease screening data collected over multiple years.
• iClass method for GEI analysis.
• Haplotype-based mapping using local genomic estimated breeding values (LGEBVs) to identify stable haplo-blocks.

Main Results:

• Five environmentally stable haplo-blocks associated with adult plant stage BLR resistance were identified: 2HS-b000305, 5HS-b001038, 5HS-b001039, 5HS-b001040, and 5HL-b001125.
• The haplo-block containing the Rph20 gene was confirmed as a key region for stable resistance.
• Novel haplo-blocks with high-effect haplotypes were discovered, offering new sources of stability.
• Environmentally specific haplo-blocks provided insights into GEI-driven resistance.

Conclusions:

• Novel haplo-blocks, in conjunction with Rph20, can significantly enhance barley leaf rust resistance.
• Haplo-block stacking demonstrated a linear relationship with improved adult plant resistance, suggesting a promising breeding strategy.
• These findings provide practical implications for developing more resilient barley cultivars and advancing breeding for complex disease resistance traits.