Integrative expression QTL-GWAS analysis reveals candidate regulators of powdery mildew (Erysiphe pisi) resistance in grass pea (Lathyrus sativus)

DISCLAIMER: These are preliminary results. Revealing genetic regulators of powdery mildew resistance in grass pea Maravilha RM1, Santos C1, Valiollahi E2, Leitão ST1, Rubiales D3, Vaz Patto MC1 [email protected] 1 Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal 2 Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran 3 Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Córdoba, Spain One major challenge in legume breeding is the improvement of resistance to threatening pathogens. Although previous studies identified molecular, biochemical and histological responses of Lathyrus sativus to Erysiphe pisi [1,2], the key players involved in regulating these responses are largely unknown. To dissect these regulatory networks, we devised an expression quantitative trait loci (eQTL) analysis approach using a worldwide L. sativus collection infected with E. pisi. Leaf transcriptomes of L. sativus accessions harvested 72 hours after E. pisi infection were sequenced, and variant calling was performed using the mapped reads, yielding high-confidence single-nucleotide polymorphism (SNP) markers within coding regions. Principal component analysis (PCA) using these SNPs revealed much genetic variation between accessions. Simultaneously, transcript abundance was quantified, generating normalised total read counts (TReC). A PCA of the expression data showed much diversity in the infection response of the genotypes, highlighting the complexity of the L. sativus-E. pisi interaction. By combining a previous powdery mildew disease severity (DS) phenotypic screening in the same accessions [1] with the here-generated SNP data, we refined the genome-wide association study (GWAS) for E. pisi response in grass pea. Moreover, the TReC phenotypic data were combined with the same SNP data for eQTL analysis. The eQTLs were then colocalised with the DS candidate genes, revealing the expression regulators of grass pea response to powdery mildew. These findings provide valuable molecular targets and markers for breeding programs to enhance powdery mildew resistance in L. sativus and related species. References: [1] D. Martins et al., 2023, ‘Lathyrus sativus resistance against the existing and emerging pathogens Erysiphe pisi and E. trifolii: A case of commonalities or total discrepancy?’, Phytopathology, vol. 113, no. 5, pp. 866–872. [2] R. M. Maravilha et al., 2025, ‘A dual transcriptome analysis reveals accession-specific resistance responses in Lathyrus sativus against Erysiphe pisi’, Frontiers in Plant Science, vol. 16, p. 1542926.