Cyst Nematodes

Roland N Perry, Maurice Moens, John T Jones, Roland N Perry, Maurice Moens, John T Jones

• Editore: CAB International
• Anno: 2018
• ISBN:
  9781786390851
• Argomento: Biological Sciences
• Categoria: Microbiology

This book is a compendium of current information on all aspects of these economically important parasites. It provides comprehensive coverage of their biology, management, morphology and diagnostics, in addition to up-to-date information on molecular aspects of taxonomy, host-parasitic relationships and resistance. Written by a team of international experts, Cyst Nematodes will be invaluable to all researchers, lecturers and students in nematology, parasitology, agriculture and agronomy, industries with an interest in chemical and biological control products for management of plant-parasitic nematodes, and any courses, quarantine and advisory services.

1 Cyst Nematodes – Life Cycle and Economic Importance

Maurice Moens^1,2, Roland N. perry^2,3 and John T. Jones^2,4,5

¹Flanders Research Institute for Agriculture, Fisheries and Food, Merelbeke, Belgium; ²Ghent University, Ghent, Belgium; ³University of Hertfordshire, Hatfield, Hertfordshire, UK; ⁴The James Hutton Institute, Invergowrie, Dundee, UK; ⁵University of St Andrews, St Andrews, UK

1.1	Introduction	1
1.2	Impact	2
1.3	History of the Genus	2
1.4	Distribution	3
1.5	Identification	3
1.6	Life Cycle	4
1.7	Syncytium	7
1.8	Effect of Abiotic Factors	8
1.9	Important Species	8
1.10	Pathotypes and Races	13
1.11	Symptoms	14
1.12	Management	17
1.13	References	18

1.1 Introduction

Cyst nematodes are remarkable parasites. They have highly specialized interactions with plants and induce the formation of a unique feeding structure, the syncytium, within the roots of their hosts. Cyst nematodes are of enormous economic importance throughout the world and the various species infect all of the world’s most important crops (Jones et al., 2013); they also share a unique feature: the ability of the female to turn her cuticle into a durable, protective capsule for her eggs. Cyst nematodes are classified within eight genera of the subfamily Heteroderinae: Heterodera, Globodera, Cactodera, Dolichodera, Paradolichodera, Betulodera, Punctodera and Vittatidera (Subbotin et al., 2010a, b). However, not all genera of the Heteroderinae are cyst forming; for example, Atalodera, Bellodera, Meloidodera and Verutus (Evans and Rowe, 1998). The most economically important species occur within the genera Heterodera and Globodera.

All cyst nematodes are obligatory endoparasites feeding within the roots of their hosts. Following fertilization and production of eggs, the body wall of the female tans and desiccates. This generates a long-lasting cyst that holds a large number of embryonated eggs, which can survive for long periods until a suitable host is available. This persistence is one of the characteristics that explain the economic importance of this group. At low nematode densities, above-ground symptoms of cyst nematode damage may be minimal. When nematode populations increase, host plants may become stunted and wilt. These symptoms are often misattributed to other abiotic factors, such as soil characteristics, mineral nutrition and water availability, or diseases.

1.2 Impact

The most damaging species include soybean cyst nematodes (SCN) (Heterodera glycines), potato cyst nematodes (PCN) (including Globodera pallida and G. rostochiensis) and cereal cyst nematodes (CCN) (including Heterodera avenae and H. filipjevi) (Jones et al., 2013). Losses caused by these and other cyst nematodes are difficult to define. PCN have been estimated to cause losses of 9% of total potato production worldwide (Turner and Subbotin, 2013). SCN are thought to be responsible for losses in excess of US$1.5 billion each year in the USA alone (Chen et al., 2001). Losses caused by CCN largely depend on environmental conditions but may sometimes exceed 90% (Nicol et al., 2011).

In addition to this direct impact on crop yield, cyst nematodes also have an indirect effect due to increased costs incurred by growers for their control and due to a reduction of product quality. Control of cyst nematodes uses a number of strategies including host resistance, prolonged rotation, chemicals, the action of biological antagonists (which may be stimulated through solarization) or trap crops (see Chapters 9 and 13, this volume). To reduce potential costs for control, quarantine status is assigned to some species. For example, PCN, a group of global importance, are native to South America (Plantard et al., 2008; Grenier, 2010) from where they were introduced in Europe along with potatoes (Turner and Evans, 1998). Because of their substantial impact on potato production and their ease of dissemination, PCN are listed as quarantine nematodes in many countries around the world (CABI, 2016a; Chapter 7, this volume). The rapid expansion in the area of soybean production in the USA that started in the mid-1900s served to establish a huge reservoir of hosts that permitted a similarly large increase in SCN (Davis and Tylka, 2000). A federal quarantine for SCN was established in 1957; however, the quarantine was lifted in 1972 because it was ineffective. It has been suggested that the movement of SCN-infested soil and plant material into new soybean production areas had already occurred before the quarantine could be established.

1.3 History of the Genus

Wouts and Baldwin (1998) wrote an excellent review of the taxonomy and identification of the cyst nematodes, including historical aspects. The following is partly inspired by this review. The first cyst-forming nematode was reported by Schacht (1859) from sugar beets that showed poor development. The nematode was later described by Schmidt (1871) as Heterodera schachtii in honour of its discoverer. During the years that followed, further cyst nematodes were reported to cause similar effects on other crops; it was believed that H. schachtii was the causal agent in all of these cases. However, when cyst nematodes collected from peas did not infect oats, a well-known host of H. schachtii, it became clear that other cyst-forming species were involved. Eventually, Liebscher (1892) described the species as H. goettingiana. Based on the host specificity of cyst nematodes, Wollenweber described the potato cyst nematode (G. rostochiensis) and oat cyst nematode (H. avenae) in 1923 and 1924, respectively (Wollenweber, 1923, 1924). All of these species were detected in Europe; H. punctata was the first cyst nematode species to be described from North America (Thorne, 1928). Being unaware of the description of H. rostochiensis, a species with a spherical cyst, the author considered the spherical shape of the cyst the basis of H. punctata. In his review of the genus Heterodera, Filipjev (1934) recognized seven cyst-forming species. Before restoration of the earlier generic name Meloidogyne by Chitwood (1949), the genus Heterodera contained both cyst-forming species of Heteroderidae and various root-knot species under the name H. marioni (Luc, 1986; Moens et al., 2009). With her monograph on the genus Heterodera, Franklin (1951) enabled the identification of ten species. However, the host range remained for several years the standard for the identification of Heterodera species. In 1959, Skarbilovich erected the subgenus Globodera to group the round cyst nematode species, including the PCN. Later, Behrens (1975) raised Globodera to generic level.

On the basis of solid morphological characters the former genus Heterodera was eventually split into the genera Heterodera, Globodera, Punctodera and Cactodera (Wouts and Baldwin, 1998). The genera Dolichodera, Betulodera, Paradolichodera and Vittatidera (each represented by one species) were added later (Turner and Subbotin, 2013). In 2017, eight genera and a total of 121 species are recognized within the cyst nematodes (see Chapter 15, this volume).

1.4 Distribution

For a long time, cyst nematodes were thought to occur only in temperate areas (Luc, 1986) or to be largely a pest of temperate regions. The first report of a cyst nematode in a tropical crop was on sugarcane in Hawaii (Muir and Henderson, 1926). When Luc (1961) reported two Heterodera species, one from swamp rice in the Ivory Coast and another from sugarcane in the Congo, it became clear that cyst nematodes could occur in the tropics. The species were described as H. oryzae and H. sacchari, respectively. Later, several other species were described from tropical crops and weeds (Fourie et al., 2017; Chapter 15, this volume). Their host range may be large (e.g. H. cajani) or restricted to a small number of plants (e.g. H. sacchari).

Within the genus Globodera, three species are of major importance: G. pallida, G. rostochiensis and G. tabacum. They are found worldwide in temperate regions or in temperate areas of tropical regions where their hosts are grown. The range of their economically important hosts is restricted to Solanaceae. The genus Heterodera contains many more species of economic importance. Species important in temperate regions are (major hosts): H. avenae (cereals), H. filipjevi (cereals), H. latipons (cereals), H. cruciferae (Cruciferae), H. glycines (legumes), H. schachtii (various) and H. trifolii (various). The following species are important in tropical regions: H. cajani (legumes), H. oryzicola (rice, banana), H. sacchari (rice, sugarcane), H. sorghi (cereals) and H. zeae (cereals).

The most important CCN, that is, H. avenae, H. filipjevi and H. latipons, differ in their distribution (reviewed by Toumi et al., 2017). Heterodera avenae was first reported in Germany and subsequently detected in most European countries. It has also been detected in Asia and South Africa, New Zealand, Peru, Canada, the Middle East, North Africa and the USA. Heterodera latipons is distributed in the Mediterranean region, but has also been detected in the former Soviet Union, Iran, Japan and Canada. Heterodera filipjevi was first reported in the Sverdlovsk reg...