Abstract
This chapter discusses the major potato diseases worldwide: late blight, early blight, wart, and powdery scab. Late blight, caused by the oomycete Phytophthora infestans, continues to be the main biotic constraint of potato production. Annual losses have been estimated to be about €6.1 billion, with major consequences to food security, especially in developing countries. Symptoms of the disease can be seen in leaves (water-soaked light to dark brown spots), stems (brown spots), and tubers (slightly depressed areas with reddish-brown color). High humidity and mild temperatures are essential for disease development and, under optimal conditions, the disease can destroy a field in a few days. Phytophthora infestans evolves continuously, mainly through recombination and migration from other areas. Thus, monitoring of P. infestans populations is critical for the design of effective management strategies. Fungicides remain as the most common tactic for late blight management, but environmental considerations are increasing the pressure to use host resistance, sanitation, and other measures. New solutions being developed to manage late blight include, among others, smart phone-based decision support systems linked to portable molecular diagnostics kits that can disseminate disease information rapidly to a large number of farmers. Emerging research topics on P. infestans include the role of the pathogen–microbiota interaction in promotion or suppression of the disease, as well as the metabolism of P. infestans.
Highlights
Introduction and Future PerspectivesSpongospora subterranea causes root hyperplasia and tuber powdery scab, leading to losses in seed and ware crops of potato worldwide and is important as the natural vector of Potato mop-top virus (PMTV), an economically important tuber blemish disease of potato found in some regions
Elicitins are an example of structurally conserved extracellular proteins of P. infestans that have a function in the sequestration of sterols from the host plant, but can act as pathogen-associated molecular patterns (PAMPs), and as such can activate PAMP triggered immunity (PTI) (Du et al 2015)
It isn’t possible to distinguish between the different Alternaria spp. causing early blight (EB) based on the symptoms even though sometimes symptoms referred to as brown leaf spot are attributed to A. alternata (Fairchild et al 2013)
Summary
The taxonomy of the plasmodiophorids is complicated and has previously been described in detail (Braselton 1995; Dick 2001; Down et al 2002). Host specificity characteristics, differences in sporangial states and habit as well as molecular data have provided additional evidence to support their placement into the species rank (i.e. S_subterranea and S. nasturtii; Bulman and Braselton 2014; Dick 2001; Gau et al 2013; Neuhauser et al 2010; Qu and Christ 2004) and they will be referred to as such hereafter. Plasmodiophorids are a monophyletic group with cruciform nuclear division, obligate intracellular parasitism, biflagellated zoospores, and environmentally resistant resting spores (Bulman et al 2001; Qu and Christ 2004). There are two major phases in the life cycle of Spongospora, each initiated by host cell infection through a single uninucleate plasmodium: in the sporogenic (spore-producing) phase, sporogenic plasmodia are located within infected plant tissue, either in tuber lesions or root, shoot or stolon galls. Following nuclear divisions within the plasmodium, thick-walled resting spores are produced, each being around 3.5–4.5 μm diameter (Jones 1978).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
