Combating potato mop-top virus: infectious clone development and screening for resistance in potato germplasms

Abstract

Potato mop-top virus (PMTV) poses a significant threat to global potato production, resulting in yield losses and quality reductions. It causes spraing symptoms in tubers. PMTV is vectored by a soil-borne protist, Spongospora subterranea f. sp. subterranean (Sss). Currently, resistance to PMTV has not been identified in potato. To facilitate studies on PMTV biology and support the identification of resistant potato cultivars, an infectious clone of PMTV was constructed. This clone, generated by synthesizing full-length cDNA and producing in vitro RNA, enables the controlled inoculation of plants for resistance screening and pathogenesis studies. Infectivity and optimal doses of the PMTV infectious clone were tested using different quantities of PMTV RNAs on Nicotiana benthamiana and a susceptible potato cultivar, Yukon Gold. In both hosts, plants inoculated with 5 µg or higher of the infectious clone developed characteristic PMTV symptoms, including leaf yellowing, stunting and reduced root development. Control plants and those treated with a lower concentration (2 µg) remained asymptomatic. Molecular analyses using polymerase chain reaction (PCR) targeting the RNA-dependent RNA polymerase (RdRp), coat protein (CP), and Triple Gene Block (TGB) genes, as well as enzyme-linked immunosorbent assay (ELISA) targeting the CP protein, confirmed systemic PMTV infection. Following successful validation, the infectious clone was used to screen a diverse collection of wild-type potato germplasms from the Solanum Petota panel for potential resistance to PMTV using quantitative PCR (qPCR). Eight species, including 14 potato lines, were identified as potentially resistant or tolerant to PMTV. This research provides a valuable tool for PMTV pathogenicity studies and resistance screening, thereby contributing to the development of effective PMTV management strategies.