Discovery and mapping of two new rust resistance genes, R₁₇ and R₁₈, in sunflower using genotyping by sequencing.

Area of Science:

• Plant Genetics and Breeding
• Agricultural Science
• Plant Pathology

Background:

• Sunflower rust, caused by Puccinia helianthi, is a major global disease threatening crop yields.
• Evolving pathogen virulence necessitates continuous discovery of diverse rust resistance sources.
• Existing rust-resistant hybrids face challenges due to rapid pathogen adaptation.

Purpose of the Study:

• To identify and characterize novel rust resistance genes in sunflower.
• To genetically map newly discovered rust resistance genes.
• To develop molecular markers for enhancing durable rust resistance in sunflower.

Main Methods:

• Identified two new rust resistance genes (R17 and R18) from South African sunflower lines (KP193, KP199).
• Developed mapping populations by crossing resistant lines with a susceptible parent (HA 89).
• Employed genotyping by sequencing (GBS) and SNP markers for precise gene mapping on chromosome 13.

Main Results:

• Successfully mapped R17 and R18 to the lower end of sunflower chromosome 13 within a gene cluster.
• Identified co-segregating SNP markers linked to R17 and R18, providing valuable genetic mapping data.
• Established genetic distances between identified genes and linked markers, facilitating marker-assisted selection.

Conclusions:

• Discovery of R17 and R18 provides new genetic resources for sunflower breeding.
• Developed molecular markers can be used to stack these genes with existing resistance for durable control.
• Mapping within a gene cluster on chromosome 13 offers insights into the genetic architecture of rust resistance.