Gene expression analysis of four Solanum tuberosum L. varieties in vitro induced with Alternaria alternata and Streptomyces werraensis extracts

Potato (Solanum tuberosum L.) is one of the major tuber food crops worldwide. However, its culture is threatened by several diseases like potato brown leaf spot which is related to Alternaria fungi. This study addresses the challenge of inducing resistance in four potato varieties against brown spot disease by in vitro culture. The approach relies on combining Streptomyces werraensis extracts, reported as potential biocontrol agents, and Alternaria alternata pathogen extracts in the potato culture medium. Initially, potato micropropagation and microtuberization media were optimized, followed by an acclimatization phase and a pathogenicity test on the four varieties (Arizona, Désirée, Spunta and Synergy). Subsequently, potato microtubers were produced in vitro, with microorganisms' extracts included in the culture medium. To assess for induced resistance, qRT-PCR analysis was conducted to evaluate gene expression levels, targeting the most relevant genes (ChtA1, ChtB3, PR1b, PRa1-like, WRKY31 and WRKY75-like). Gene expression analysis revealed significant differences between varieties, with Arizona variety showing the most vigorous response. These distinct varietal responses indicate genotype-specific reactions to the combined treatment of A. alternata and S. werraensis extracts. This research highlights the S. werraensis potential as a biocontrol agent to induce resistance in potatoes to A. alternata. The results support the integration of in vitro culture media supplemented with microorganism extracts for large-scale standardized potato production.