Molecular Pathogens, 2025, Vol.16, No.4, 147-158 http://microbescipublisher.com/index.php/mp 148 sensitivity and automation potential, there is a problem of insufficient sensitivity for low concentrations of initial infection and shellless virus-like detection. With the development of molecular biology, nucleic acid-based molecular diagnostic technology has greatly improved the sensitivity and specificity of plant virus detection (Prinz et al., 2022). In addition, with the increase in international seed potato trade and transportation, quarantine departments of various countries are highly dependent on molecular testing methods to conduct virus testing of seed potatoes and tissue culture seedlings entering and leaving the country to prevent the spread of quarantine viruses. 2 The Molecular Biology Foundations of Potato virus 2.1 Viral genome structure and coding characteristics Most potato viruses are sense single-stranded RNA (+ssRNA) viruses, with different genome size and coding strategies. Taking potato Y virus (PVY) as an example, its genome is a single strand positive-strand RNA with a total length of about 9.7 kb and a long open reading frame. It translates to produce a polyprotein of about 350 kDa. It is then cut into 10 functional proteins by the virus-encoded protease into 10 functional proteins, including coat protein (CP), cofactor HC-Pro, nuclear sheath protein, etc. (Tam et al., 2012; Bartola et al., 2020). The genome of potato X virus (PVX) is about 6.4 kb, which is also +ssRNA, but the multi-open reading frame strategy is adopted to encode 5 proteins: the 5'-end ORF1 encodes RNA-dependent RNA polymerase (RdRp), the three ORF2-4 in the middle form a "tertiary gene cluster" that encodes three proteins related to movement (TGBp1-3), and the 3'-end ORF5 encodes the coat protein. The genome of potato leaf roll virus (PLRV) is smaller, about 5.9 kb, encodes a few proteins and needs to be reproduced by the host phloem cell environment. Potato M virus (PVM) and S virus (PVS) belong to the genus Carlavirus, with a linear +ssRNA, a length of about 8.5 kb, and contains 6 ORFs, presenting the typical genomic tissue structure of this genus virus. In addition, potato spindle tuber virus (PSTVd) is a circular single-stranded RNA with only about 360 nucleotides, which does not encode a protein but can interfere with host metabolism (Qian and Huang, 2025). 2.2 The relationship between viral mutation, recombination and pathogenicity Potato viruses have produced abundant genetic variations in long-term evolution, and the pathogenicity of different strains and variant types tends to vary significantly. Taking PVY as an example, it is traditionally divided into three types: ordinary strain O, tobacco ordinary strain N, and chlorosis strain C according to serology and gene sequence. However, in recent years, many studies have shown that PVY can derive new recombinant strain types through gene mutations or recombination between different strains. These recombinant lines tend to exhibit novel biological properties and pathogenicity (Samarskaya et al., 2024). Viral recombination and mutations increase the complexity of diagnosis and may also break through the resistance of host varieties. The study found that different PVY lines have amino acid mutations in viral-causing genes such as genome P1, HC-Pro, and NIa, which determine the pathogenicity of the virus and the host range of infectiousness. In addition to PVY, different lines of potato X virus (PVX) also have genetic mutations between mild and severe strains, and when infected with PVA or PVY in combination can lead to "curve leaf mosaic disease" or even plant death. In the fields, potato plants are often infected by multiple viruses. Some surveys have found that it is not uncommon for a single potato to be infected with 2~3 viruses at the same time, and even a very small number of plants can carry 4~5 viruses (Rashid et al., 2021). Multiple infections may lead to recombination and interaction between viruses, enhancing pathogenicity to plants. 2.3 Molecular mechanisms of virus interaction with host There is a complex molecular interaction between potato viruses and host plants. On the one hand, viruses need to replicate and move using the host's organelles and enzyme systems; on the other hand, plants evolve antiviral defense mechanisms, including resistance gene-mediated resistance responses and RNA silencing. Studies have shown that there are multiple antiviral genes (resistance R genes) in potatoes. These R genes usually encode NBS-LRR-like resistance proteins, which can recognize virus-specific pathogenic factors and trigger defense responses such as hypersensitivity reactions (HR), limiting the virus in the early stages of invasion (Yin et al., 2017; Chen et al., 2022). Potatoes also inhibit viruses through RNA silencing mechanisms: When viral RNA
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