In vivo and In vitro Infection of Potato Roots with Plant Parasitic Nematodes for the Assessment of Induced Structural Changes

Abstract

Soil-dwelling plant parasitic nematodes (PPNs) are important potato pests that cause lesions and/or change plant roots structure, leading to reduced crop fitness and productivity. Research on the cellular and subcellular mechanisms of PPNs infection and development can resort to field plants or seedlings under greenhouse conditions. Field studies are more representative of natural environments but are subjected to the unpredictability of environmental conditions that can heavily influence research outcomes. Greenhouse studies allow higher control over environmental variables and higher safety against contaminants or pathogens. However, in some hosts, genetic diversity becomes an important factor of variability and influences the host-parasite complex response. We have developed in vitro co-cultures of transgenic roots with PPNs as a reliable alternative that occupies less space, requires less time to obtain, and is free from contamination or from host genetic variability. Co-cultures are obtained by introducing aseptic PPNs to host in vitro transgenic roots. They can be maintained indefinitely, which makes them excellent support for keeping collections of reference PPNs. In the present work, a protocol is detailed for the controlled infection of in vivo potato roots with the root lesion nematode and for establishing in vitro co-cultures of potato transgenic roots with the root-knot nematode. The in vitro co-cultures provided a laboratory proxy for the natural potato infection condition and produced nematode life stages irrespective of season or climate conditions. Additionally, the methodology used for structural analysis is detailed using histochemistry and optical microscopy. The acid fuchsin dye is used to follow nematode attack sites on roots, while differential staining with Periodic acid-Schiff (PAS) and toluidine blue O highlights nematode structures in potato internal root tissue.