Morphological and Molecular Characterization of Gymnosporangium spp. Causing Rust Disease on Rosaceous Trees

Abstract

Rust diseases caused by species of Gymnosporangium are among the most important fungal diseases affecting rosaceous trees, resulting in significant ornamental, ecological, and economic losses. These pathogens are characterized by complex life cycles involving alternate hosts and are responsible for symptoms such as leaf spots, gall formation, defoliation, and reduced plant vigor. Accurate identification and characterization of Gymnosporangium species are essential for understanding disease epidemiology and developing effective management strategies. The present study was conducted to investigate the morphological and molecular characteristics of Gymnosporangium spp. associated with rust disease on rosaceous trees. Diseased plant samples exhibiting typical rust symptoms were collected from affected orchards and ornamental landscapes. Fungal structures, including telia, aecia, and spores, were examined microscopically to assess morphological variation among isolates. Molecular characterization was performed using polymerase chain reaction (PCR) amplification and sequencing of conserved genomic regions, followed by phylogenetic analysis to determine species identity and genetic relationships. The results confirmed the association of multiple Gymnosporangium species with rust disease symptoms on rosaceous hosts. Morphological observations revealed variation in spore size, shape, and reproductive structures among isolates, supporting species-level differentiation. Molecular sequence analysis demonstrated high similarity between the obtained isolates and previously reported Gymnosporangium species from different geographic regions. Phylogenetic analysis further revealed genetic diversity within the collected isolates and identified close evolutionary relationships among rust pathogens infecting rosaceous plants. Environmental conditions such as humidity and moderate temperature were found to favor disease development and pathogen spread. The findings of this study provide important insights into the taxonomy, diversity, and epidemiology of Gymnosporangium spp. affecting rosaceous trees. Accurate morphological and molecular identification of these rust pathogens is essential for improving disease diagnosis, monitoring pathogen distribution, and developing sustainable management practices for the protection of rosaceous tree species in orchard and landscape ecosystems.