Identification of physiological races of Puccinia striiformis f. sp. tritici and molecular docking of some biological treatments as prospective fungal inhibitor candidates in wheat

Abstract Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst), represents one of the most significant challenges to the world’s wheat production. This study aimed to investigate five aggressive physiological races of Pst impacting significant wheat cultivars in Egypt’s northern Delta, which are essential for breeding programs. Moreover, the study evaluated the antifungal activity and mechanisms of action of chitosan nanoparticles, Trichoderma harzianum , and Sargassum latifolium against Pst using molecular docking analysis. During the 2024 growing season, an increase in the virulence of newly identified aggressive Pst races in Egypt was detected. A total of 20 and 23 races were recognized from 89 out of 132 samples in 2023 and 86 out of 115 samples in 2024, respectively. In addition, twenty Egyptian wheat cultivars and fifty-two CIMMYT nursery lines were screened at the Sakha Agricultural Research Station for resistance to five aggressive stripe rust races at both seedling and adult stages. The results revealed that most cultivars were susceptible, with only two (10%) and five (25%) displaying resistance. Among the CIMMYT entries, 17 (33%) and 21 (40%) confirmed resistance in 2023 and 2024, respectively. Single nucleotide polymorphism (SNP) markers were used to identify the five Pst races, and phylogenetic analysis was conducted using representative fungal species from genomic databases. The five aggressive races were deposited in the GenBank database under accession numbers PV983376, PV983377, PV983378, PV983379, and PV983380. Biological treatments using S. latifolium , T. harzianum , and chitosan nanoparticles significantly decreased stripe rust disease severity. These findings recommend that such treatments can support high-quality wheat flour production and serve as safe, environmentally friendly alternatives to synthetic fungicides. Molecular docking analysis further elucidated the mechanisms of antifungal action, particularly highlighting the effectiveness of S . latifolium and T. harzianum against Pst races. Overall, this investigation exhibits strong potential for improving wheat cultivars with enhanced yield and resistance to aggressive stripe rust races, contributing to sustainable disease management strategies.