Study on Leaf Rust Resistance in Populus Germplasm Resources Based on Multimodel GWAS and Selective Sweep Analysis

Area of Science:

• Plant Pathology
• Forest Genetics
• Molecular Biology

Background:

• Leaf rust poses a significant threat to poplar (Populus) trees globally.
• Developing disease-resistant poplar varieties is crucial for forestry and ecological health.
• Understanding the genetic basis of poplar leaf rust resistance is essential for breeding programs.

Purpose of the Study:

• To screen a diverse collection of 135 Populus germplasm resources for leaf rust resistance.
• To identify genetic loci and candidate genes associated with leaf rust resistance in poplar.
• To provide genetic resources for the development of rust-resistant poplar varieties.

Main Methods:

• Phenotypic screening of 135 poplar clones for leaf rust resistance.
• Genome-wide association studies (GWAS) using single and multi-locus models.
• Selective sweep analysis, including Cross-population composite likelihood ratio (XP-CLR) analysis.
• Haplotype analysis, Sanger sequencing, and quantitative real-time PCR (qRT-PCR).

Main Results:

• Significant variation in leaf rust resistance was observed across different poplar clones and sections.
• GWAS identified 7 significant loci associated with leaf rust resistance.
• XP-CLR analysis detected 388 positively selected regions.
• The gene BBX29, located upstream of a key resistance locus (Chr13_14699534), showed lower expression in resistant clones.
• Six potential candidate genes for leaf rust resistance were identified by integrating GWAS and XP-CLR data.

Conclusions:

• This study successfully screened poplar germplasm for leaf rust resistance and identified key genetic regions and candidate genes.
• The BBX29 gene is a strong candidate for its role in poplar leaf rust resistance.
• The findings offer valuable genetic insights and resources for breeding rust-resistant poplar trees.