Morphological Diversity of Epichloë sinensis from Festuca sinensis Germplasm on the Qinghai–Tibet Plateau

Epichloë sinensis engages in mutualistic symbiosis with Festuca sinensis on the Qinghai–Tibet Plateau. The influence of variation within the Epichloë genus on morphology in this context is poorly understood, as is the influence of environmental factors (e.g., temperature, precipitation, and altitude). Accordingly, a total of 122 fungal endophyte strains were isolated from 270 F. sinensis seeds collected from different locations on the Qinghai–Tibet Plateau, and their morphological characteristics were observed. The colonies were white on the front, dark brown in the center on the back, and light brown or yellow around the PDA medium, exhibiting typical characteristics of E. sinensis. Morphological diversity was categorized into (1) colony features (six types based on texture, shape, and cracks), (2) growth rates (51 strains that produce spores: 0.23–0.78 mm/d; 71 strains that do not produce spores: 0.11–0.93 mm/d), and (3) hyphal width (51 strains that produce spores: 0.60–2.57 μm; 71 strains that do not produce spores: 0.95–2.10 μm). Correlation analyses revealed that temperature and altitude had significant effects on these traits. Phylogenetic relationships showed that 17 strains probably were E. sinensis, and only 4 strains probably were the endophyte E. poae. One strain was haploid and may have originated from E. festucae. All 22 tested strains lacked genes associated with toxic alkaloid biosynthesis (ergot alkaloid) but harbored regulatory genes for the insect-resistant alkaloid peramine, demonstrating potential for use in developing new germplasm in Festuca species.