A rapid and efficient method to evaluate the infection of major DNA viruses in sweet potato seedlings and tubers

Abstract Background Sweet potato is an important food crop in China which is the fifth largest staple crop next to rice, wheat, maize, and soybean. Recent years the destroy infecting by DNA viruses in sweet potato was more and more serious. Three DNA viruses (sweepoviruses, Badnavirus and Mastrevirus) are major agents in viral diseases of sweet potato in China. It is necessary to establish a rapid and efficient method to evaluate the health of sweet potato seedlings and tubers,which will greatly affect the yield, quality of tubers and seeding circulation of sweet potatoes. Sweepoviruses were a group phylogenetically distinct from other begomoviruses that infects plants of the family Convolvulaceae including sweet potato. Sweet potato symptomless virus 1 (SPSMV-1) is the only species of Mastrevirus which can infected sweet potato. Sweet potato Badnavirus B (SPBV-B) are non-enveloped bacilliform DNA viruses with a monopartite genome which belonged to the genus Badnavirus of the family Caulimoviridae and was first found in sweet potato in 2009. As the mixed infection of these viruses is very common, rapid detection is required for etiologic diagnosis. Results In this study, a rapid and efficient method to evaluate the infection of major DNA viruses (sweepoviruses, Badnavirus and Mastrevirus) in sweet potato seedlings and tubers was developed and applied. A mixture of three pairs of primers was used for amplification of viral nucleic acids, yielding three different amplicons with sizes of 750 bp, 147 bp and 396 bp for sweepoviruses, Badnavirus and Mastrevirus respectively. The specificity and sensitivity of multiplex PCR were also evaluated. A total of 65 sweet potato samples with virus-like symptoms cuttings and storage roots from Henan province in China were collected between June 2019 and July 2021. They were tested for the presence of three DNA viruses by multiplex PCR which showed sweepoviruses, Badnavirus and Mastrevirus infections were 60.0%, 36.7%, and 43.3% respectively. Co-infections with three viruses, sweepoviruses and Badnavirus, sweepoviruses and Mastrevirus, Badnavirus and Mastrevirus were identified in different samples (the detection ratio of co-infections was 13.3%, 20.0%, 13.3%, and 10.0% respectively). Conclusions In the current situation of frequent virus mixed infection in sweet potatoes, this method is the first report on a simple assay and may be a potentially useful for apid and efficient method to evaluate the infection of major DNA viruses in sweet potato seedlings and tubers in China.