Early Detection and Temporal Dynamics of Pratylenchus scribneri Infection in Potato Roots Determined Using Quantitative PCR and Root Staining

Abstract

The root-lesion nematode, Pratylenchus scribneri, is a migratory endo-parasitic nematode that impacts potato production on a large scale. Effective management of this nematode requires an understanding of its population dynamics alongside early detection. Typically, the nematode population estimates are made from infested soil; however, considering the endo-migratory lifestyle of this nematode, it also is crucial to determine the nematode population residing inside the host roots. In this study, a SYBR green-based quantitative real-time PCR (qPCR) assay was developed for detection and quantification of P. scribneri in potato roots. The assay used a previously reported primer pair (ITS-2F/ITS-2R), and it proved to be specific and sensitive, detecting as low as 1/128th equivalents of a P. scribneri individual per 0.2 g of potato roots. The robustness of the assay was reflected in high correlation observed between the P. scribneri densities determined microscopically and the densities detected by qPCR in artificially inoculated (R2 = 0.93) and naturally infected (R2 = 0.73) root samples. A time-course experiment conducted in the greenhouse using qPCR detected P. scribneri in potato roots as early as 5 days after planting. The results correlated well with the microscopic observations (R2 = 0.80) and were complemented further with root staining. Additionally, three P. scribneri reproduction peaks were observed during one 3-month growth cycle of potato. Overall, the assay developed in this study is specific to P. scribneri in DNA extracts of root tissue and allows early detection and understandings of reproduction timings of this important nematode of potato.