An evaluation of the implications of virulence in non-European populations of Globodera pallida and G. rostochiensis for potato cultivation in Europe

Abstract

The potato cyst nematodes Globodera pallida and G. rostochiensis are listed in the EU Plant Health Directive 2000/29/EC and are also subject to the new EU Council Directive 2007/33/EC on the control of potato cyst nematodes, requiring unilateral suppression of these pests in Europe. At the same time there is also pressure to increase world trade in potatoes. Such pressure has to be balanced by the risks involved in the associated spread of these pests and subsequent problems in management. Populations of the potato cyst nematodes from outside Europe, in particular South America, which is considered the origin of G. pallida and G. rostochiensis, pose a risk to those European countries where limited genetic variability of these nematode species has been recorded. The development and usage of resistant cultivars under such conditions has formed a pivotal role in integrated management programmes in Europe. Molecular studies have shown that populations of G. pallida and G. rostochiensis from South America have a different genetic composition from those in Europe. The introduction of such populations would pose a threat to the use of resistant cultivars as a major tool in reducing the potential spread and damage caused by these species. At present, an inability to link precisely genetic variability to the virulence characteristics of a specific nematode population, and quickly identify the virulence status of intercepted populations for inspection purposes, strengthens the case for using plant health legislation to prevent their introduction.

The genome and life-stage specific transcriptomes of Globodera pallidaelucidate key aspects of plant parasitism by a cyst nematode

“…Yield losses of potato in excess of 50% due to PCN are reported in the literature (for example, [5]). Although PCN is indigenous to South America, it was introduced into Europe in the 19th century with potato material used for resistance breeding against late blight [6] and is now widely distributed in Europe [7]. From here, PCN has spread to all major potato growing areas of the world including Ukraine and, more recently, Idaho in the USA [8,9].…”

Only a small subset of the SPRY domain gene family in Globodera pallida is likely to encode effectors, two of which suppress host defences induced by the potato resistance gene Gpa2

“…They originate in the Andean region of South America but are now distributed almost everywhere that potato is grown (Turner & Evans, 1998). PCN is present across much of the EU and in many other important potatogrowing regions including Ukraine and the USA state of Idaho (Hockland et al, 2012). Infected plants are stunted and yellow, and may die off entirely if heavily Trait Loci (QTL), making it more difficult to breed than monogenic sources (Bakker et al, 2006).…”

Resistance genes against plant-parasitic nematodes: a durable control strategy?

“…The geographical variation in cyst nematode genetic diversity and capacity for gene flow emphasise the importance of stringent quarantine measures. New introductions of cyst nematodes from South America to Europe and North America have the potential to introduce new resistance-breaking genotypes, rendering the currently employed resistant cultivars defective (Hockland et al, 2012). Multiple introductions of G. rostochiensis into Europe are believed to be responsible for the differences in durability of the H1 gene in the UK in comparison to other European countries (Bakker et al, 1993;Bakker, 2002).…”