Top 10 plant-parasitic nematodes in molecular plant pathology

Abstract

The aim of this review was to undertake a survey of researchers working with plant-parasitic nematodes in order to determine a 'top 10' list of these pathogens based on scientific and economic importance. Any such list will not be definitive as economic importance will vary depending on the region of the world in which a researcher is based. However, care was taken to include researchers from as many parts of the world as possible when carrying out the survey. The top 10 list emerging from the survey is composed of: (1) root-knot nematodes (Meloidogyne spp.); (2) cyst nematodes (Heterodera and Globodera spp.); (3) root lesion nematodes (Pratylenchus spp.); (4) the burrowing nematode Radopholus similis; (5) Ditylenchus dipsaci; (6) the pine wilt nematode Bursaphelenchus xylophilus; (7) the reniform nematode Rotylenchulus reniformis; (8) Xiphinema index (the only virus vector nematode to make the list); (9) Nacobbus aberrans; and (10) Aphelenchoides besseyi. The biology of each nematode (or nematode group) is reviewed briefly.

Figure 1

Interrelationships of nematode clades (Van Megen et al., 2009) with phylogenetic positions and feeding apparatus of plant‐parasitic nematodes indicated. ‘Infraorders’ (a less common taxonomic unit) are indicated in red type.

Figure 2

Damage caused to roots of tomato (Solanum lycopersicum) by the root‐knot nematode Meloidogyne incognita in Ethiopia. (Photograph courtesy of Seid Awol, Ghent University, Ghent.)

Figure 3

Syncytium induced by the potato cyst nematode Globodera rostochiensis in the roots of potato.

Figure 4

Targeting of the nucleus and nucleolus of a Nicotiana benthamiana cell by a Globodera pallida effector of unknown function fused to green fluorescent protein. The nuclei are labelled with a monomeric red fluorescent protein (mRFP)–histone fusion (Martin et al., 2009). Autofluorescence from chloroplasts is shown in blue.

Figure 5

Patches of stunted wheat plants infected with root lesion nematodes Pratylenchus spp. [Photograph courtesy of Sarah Collins, Department of Agriculture and Food, Government of Western Australia (DAFWA)].

Figure 6

Uptake of fluorescein isothiocyanate (FITC) (green) in a solution of double‐stranded RNA (dsRNA) by Pratylenchus (Tan et al., 2013).

Figure 7

Acid fuschin‐stained Radopholus similis in roots of Medicago sativa.

Figure 8

Narcissus bulb with accumulation of Ditylenchus dipsaci fourth‐stage juveniles as dry eelworm wool, and an inset showing a transmission electron microscope image of the eelworm wool with coiled, clumped individuals. (Photographs courtesy of Roland N. Perry, Rothamsted Research, Harpenden, UK; Perry and Moens, 2011b.)

Figure 9

Damage to pine trees caused by Bursaphelenchus xylophilus. (Photograph courtesy of Takuya Aikawa, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan.)

Figure 10

Diagram summarizing the life cycle of the pine wilt nematode Bursaphelenchus xylophilus.

Figure 11

Acid fuschin‐stained adult females of Rotylenchulus reniformis, showing the characteristic body shape for which the species is named.

Figure 12

Parasitism of Xiphinema index in roots of Vitis spp. (A) Typical root symptoms showing swellings of root tips in comparison with an uninfected root. (B) Multinucleate cells induced by X. index in Vitis rootstock Paulsen 1103 (V. berlandieri × V. rupestris). (Photographs courtesy of Dr P. Castillo and Dr N. Volvas, Institute for Sustainable Agriculture‐CSIC, Córdoba, Spain, and Istituto per la Protezione delle Piante, Bari, Italy.)

Figure 13

Nacobbus aberrans s.l. on tomato, illustrating the origin of the common name of this nematode (the false root‐knot nematode). Although the symptoms of N. aberrans infection resemble those of root‐knot nematodes, biotrophic parasitism has evolved independently in Nacobbus. (Photograph courtesy of Carmen Triviño, INIAP, Ecuador.)

Figure 14

Symptoms of Aphelenchoides besseyi on rice. (Photograph courtesy of Donald Groth, Louisiana State University AgCenter, Bugwood.org.)