Occurrence of Potato Viruses in Taiwan and Biological and Molecular Characterization of Potato Virus Y Isolate

Potato production has long been threatened by viral diseases, particularly potato leafroll virus (PLRV) and potato viruses A, M, S, X, and Y (PVA, PVM, PVS, PVX, and PVY). However, current information on the occurrence of potato viruses in Taiwan is limited, and the biological and molecular characteristics of locally occurring virus isolates are poorly understood. To determine the current occurrence and characteristics of potato viruses in Taiwan, a four-year field survey (2023-2026) was conducted in commercial potato production fields across major potato-growing regions. PVY was the most frequently detected virus (46%), followed by PVS (5.1%). Subsequent strain typing showed that recombinant PVY strains predominated, with PVY SYR-I (25.1%), PVY SYR-II (13.7%), and PVY N-Wi (13.3%) being the most frequently detected strain groups. Among the tested isolates, PVY-33, a PVY N-Wi isolate, caused the most pronounced symptoms in Nicotiana benthamiana and induced severe systemic leaf deformation in potato cv. Kennebec. Based on this pronounced biological phenotype, PVY-33 was selected for construction of a full-length infectious cDNA clone, providing a genetically defined and reproducible inoculum source. The infectious clone-derived virus reproduced the PVY-33 phenotype and reduced tuber yield by approximately 50% in both cv. Kennebec and cv. Atlantic. Whole-genome phylogenetic analysis supported the notion that PVY-33 is closely related to PVY N-Wi isolates from the United States. Together, these findings provide an updated understanding of potato virus occurrence and PVY strain composition in the surveyed fields and provide important information about the biological and molecular characteristics of a locally derived PVY isolate.