A candidate for Lr19, an exotic gene conditioning leaf rust resistance in wheat

Area of Science:

• Plant genetics
• Molecular biology
• Crop science

Background:

• Leaf rust poses a significant threat to wheat production worldwide.
• The Lr19 gene from Thinopyrum ponticum provides broad-spectrum resistance to leaf rust in wheat.
• Understanding the molecular basis of Lr19-mediated resistance is crucial for breeding resistant wheat varieties.

Purpose of the Study:

• To isolate and characterize the gene responsible for Lr19-mediated leaf rust resistance in durum wheat.
• To determine the molecular structure and evolutionary relationship of the resistance gene.
• To investigate the expression pattern of the identified resistance gene.

Main Methods:

• NBS profiling using PCR amplification of conserved nucleotide-binding site (NBS) motifs.
• Isolation and sequencing of differential PCR products from durum wheat-Th. ponticum recombinant lines.
• Obtaining full-length cDNA and analyzing the deduced amino acid sequence.
• Homology searches and quantitative PCR (qPCR) for gene expression analysis.

Main Results:

• A novel gene, designated AG15, was identified and found to be tightly linked to Lr19.
• AG15 encodes a 1,258 amino acid protein with characteristic NBS-LRR domains and a coiled-coil (CC) region.
• AG15 shares homology with known wheat resistance genes (Pm3a, Lr1, Lr21, Lr10) and is constitutively expressed in Lr19 carriers.

Conclusions:

• AG15 is likely the gene conferring Lr19-mediated leaf rust resistance in durum wheat.
• The identified NBS-LRR gene provides a valuable target for marker-assisted selection and breeding for durable leaf rust resistance.
• Constitutive expression of AG15 suggests its role in basal defense mechanisms against leaf rust.