Morphological Profiling, Pathogenic Diversity, and Genetic Assessment of Drechslera teres Isolates in Barley Using Internal Transcribed Spacer (ITS) Analysis

This study evaluated the morphological, pathogenic, and genetic diversity of six Pyrenophora teres Drechsler (anamorph: Drechslera teres (Sacc.) Shoem.) isolates (N1–N6) collected from various Egyptian governorates. The isolates were identified as Pyrenophora teres through nrDNA-ITS sequencing and deposited in NCBI GenBank. Morphological analysis on potato dextrose agar (PDA) revealed variability in mycelial color (olivaceous in N1, N4, N6; gray in N2, N3, N5), colony texture (highly floccose in N1, N2, N6; moderately floccose in N3, N5; sparsely floccose in N4), and unique pigmentation in isolate N4. Pathogenicity tests on the barley cultivar Giza 2000 showed significant differences among isolates: disease incidence (DI%) ranged from 33.33% (N3) to 86.33% (N2) and disease severity percentage (DS%) from 11.75% (N3) to 67.50% (N2). The sizes of the amplified ITS fragments varied from 502 to 566 bp, suggesting minor genetic polymorphisms. Phylogenetic analysis and BLAST comparisons with global isolates indicated high sequence similarity (99.12%–99.82%). A heatmap analysis further highlighted the close genetic relatedness among the Egyptian isolates and their divergence from non-Egyptian strains. These findings contribute to the fungal taxonomy of D. teres and support the identification of native strains for agricultural applications. The deposition of sequences in GenBank facilitates global research on this pathogen.