Molecular studies on root lesion nematode resistance in cereals
My work consisted of three main work packages. The first focused on developing a RT-qPCR detection assay to identify and quantify Pratylenchus neglectus in infected cereal roots. I evaluated species-specific primers and root lesion nematode sequences, selecting the optimal primer combination for its high specificity and sensitivity. The SYBR® Green-based RT-qPCR detection assay could detect DNA from a single nematode in water suspension or as few as 250 nematodes within roots, outperforming traditional visual counting methods by detecting eggs, inactive and/or dead nematodes. This assay is promising for plant breeding, enabling fast screening of large plant populations. In the second work package, I assessed the pathogenicity of P. neglectus multiplied under various pre-cultivation methods. Nematodes grown on carrot callus for a long period of time showed reduced pathogenicity compared to those cultured on host plants, evidenced by higher Cq values, fewer nematodes, and lower infection rates. Factors such as the tripartite interaction of plant host-pathogen-microbiome, available nutrients to the plant and nematode, and phenotypic plasticity likely contribute to this decline in pathogenicity. These findings are crucial for plant breeding, as maintaining a consistent and pathogenic inoculum is vital for the infection test. The third work package involved a genome-wide association study (GWAS) on a global collection of barley accessions infected with P. neglectus. The developed RT-qPCR detection assay allowed for rapid and reliable quantification of nematode. A significant SNP associated with resistance was identified on chromosome 3H, along with 38 candidate genes, including six involved in plant defense. This study provides insights into the genetic basis of barley resistance to P. neglectus and supports the use of marker-assisted selection to enhance resistance in barley cultivars.
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