Grapevine l eaf rust (GLR) c aused b y Phakopsora euvitis diminishes fruit quality and reduces yield in viticulture, making it one of the world’s most significant fruit crop threats. To develop GLR-resistant grape varieties, substantial efforts have been made to select rust-resistant genes and determine effective strategies f or achieving durab le resistance in grapevines. This study aims to identify genetic resources resistant to GLR by investigating disease incidence in vineyards and symptom development in grapevines inoculated with pathogens. Fifty-seven genotypes from Ampelopsis brevipedunculata, Vitis acerifolia, V. aestivalis, V. amurensis, V. cinerea, V. coignetiae, V. flexuosa, V. labrusca, V. labruscana, V. rotundifolia, and V. vinifera were evaluated for rust disease incidence over four years (2021 –2024) at Yeunganm University. Three plants per genotype were potted and sprayed with a pathogen suspension to assess disease incidence on their adaxial leaf surfaces in a greenhouse. Variation in resistance to GLR was observed among genotypes within each species. Resistant genotypes of V. coignetiae exhibited no symptoms on their leaves, while severe infections were noted in the leaves of susceptible genotypes of A. brevipedunculata, V. amurensis, V. flexuosa, V. labruscana, and V. vinifera. None of the tested V. rotundifolia genotypes displayed yellow pustules and remained unaffected for three weeks after artificial inoculation. These findings highlight the potential of V. rotundifolia and V. coignetiae as valuable genetic resources for breeding rust-resistant grapevines. Chlorophyll content was comparable across all uninfected genotypes. While resistant genotypes maintained relatively stable chlorophyll levels, the average chlorophyll content in the majority of susceptible genotypes was significantly lower following inoculation than before. This negative relationship indicates a general decline in photosynthetic capacity due to disease development in grapevines. Identifying resistant genotypes among both resistant and susceptible genotypes across different Vitis species provides crucial insights for developing new grape varieties with improved resistance to GLR.

Grapevine leaf rust (GLR) caused by Phakopsora euvitis results in the reduction of fruit quality and yield loss in grape production. The purpose of this study was to investigate the expression of genes related with defense responses in the grapevines infected with rust pathogens. In two genotypes of Ampelopsis species inoculated with P. euvitis, the real-time PCR with RNAs was performed to investigate transcripts levels of nine defense-related genes, including pathogenesis-related 1 (PR1), β-1,3glutannase (Glu), chitinase (Chi), superoxide dismutases (SOD), glutathione peroxidase (GPX), phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), stilbene synthase 1 (STS1), and resveratrol O-methyltransferase (ROMT). All tested genes were upregulated in YG11030 as well as YG10075, while mostly the expression of genes was higher in YG10075 than that in YG11030. Glu and STS showed significantly high expression in YG10075 than in YG11030. Expression of ROMT was upregulated in YG11030 and downregulated in YG10075 at 24 hours after inoculation. The differential expression pattern of the tested genes seems to be related with the defense responses, considered to be involved in plant-resistant responses against the infection by P. euvitis, and further studies on resistant responses based on the expression of genes would provide valuable information in breeding grapes resistant to diseases.