Agriculture Reference
In-Depth Information
bradys
(Steiner and Lehew, 1933) Andrássy, 1958,
was reported as a new potential threat to potato
production in West Africa (Coyne and Claudius-Cole,
2009; Coyne
et al
., 2011). In the tropics, several
species are found associated with potato, but the
root-knot nematodes (RKNs) (
Meloidogyne
incognita
(Kofoid and White, 1919) Chitwood and
Meloido-
gyne
javanica
(Treub, 1885) Chitwood, 1949) and
lesion nematodes (
Pratylenchus
brachyurus
(God-
frey, 1929) Filipjev & Schuurmans Stekhoven,
1941, and
Pratylenchus
coffeae
Goodey, 1951) are
particularly important. The shifting of the main
regions for potato production to Asia, Africa, and
Latin America, in line with the growing import-
ance of potato as a staple crop in these regions,
movement of commodities through trade, which
could lead to the introduction of new pests and
diseases, and climate change are all factors that
will determine nematode threats in the future.
This chapter describes the current main nema-
tode parasites of potato and discusses options for
their management. There are many sources of
additional information in the literature, and dis-
tribution maps and host range information can
be accessed at
http://www.cabi.org/dmpd.
southern Peru (Plantard
et al
., 2008). Recently
another species that infects potato,
Globodera
ellingtonae
n. sp. (Handoo
et al
., 2012), was found
in Oregon and Idaho, USA and similar isolates
are reported from Chile and Argentina. The
pathogenicity of this species is currently under
investigation. Given the diversity of these cyst
nematodes in S. America it is likely that further
species will be described in the future.
PCNs have a host range restricted to the
Solanaceae that includes potato, tomato, and au-
bergine, and weeds such as deadly nightshade,
and have highly specialized interactions with
their hosts, requiring the formation of a feeding
site (syncytium). The cyst, which is formed from
the dead body wall of the female, forms a protect-
ive container for the
200-
500 eggs. The sec-
ond-stage juveniles within the eggs can remain
dormant for many years, until stimulated to
hatch by root diffusate from the host. The juven-
iles enter the root near the tip, puncturing the
epidermal cell walls with their stylet, and then
continue through internal cells before becoming
sedentary and establishing a feeding site from a
cortical parenchyma or endodermis cell (Sobczak
and Golinowski, 2011). The syncytium develops
following the partial degradation of cell walls ad-
jacent to the initial cell, creating a multinucleate,
metabolically active sink. They feed from the syn-
cytium, developing into males or females after
the fourth molt, depending on environmental
conditions (Ellenby, 1954; den Ouden, 1960).
The vermiform males leave the roots and fertilize
the rotund females that protrude from the roots,
fertilized eggs develop within the female, the fe-
male dies, and then her tanned cuticle forms the
cyst (
Fig. 10.1
). The cysts facilitate persistence
and dispersal, adhering to tubers, soil, farm ma-
chinery and equipment, and within which the
eggs can remain viable in the soil for many years.
PCNs are estimated to cause yield losses of
up to 10% worldwide (Oerke
et al
., 1994). Des-
pite efforts to prevent their spread, they are now
found in many potato growing regions world-
wide, though major production areas including
China and Brazil have not reported having PCNs.
They are designated as A2 quarantine organ-
isms in Europe and EPPO-region countries, and
measures are taken to prevent their import and
regulate their spread. Heavily infested fields can
show serious plant damage; however, poor growth
in patches is more typical, with yellowing, wilt-
ing, or death of the leaves. Damage can also be
10.1
Plant Parasitic Nematodes
of Potato
Potato cyst nematodes,
Globodera
rostochiensis
,
Globodera pallida
and
Globodera ellingtonae
The yellow and white potato cyst nematodes
(PCNs),
Globodera rostochiensis
(Wollenweber,
1923) Behrens, 1975, and
G. pallida
have coev-
olved with Solanaceae plants in the Andes in South
America, where they are indigenous in this moun-
tainous region with a temperate climate (Stone,
1979, 1985). They were probably introduced
into Europe around 1850 with potato breeding
material (Jones and Jones 1974), from where they
were further dispersed around the world. A patho-
type scheme was devised by Kort
et al
. (1977), and
further pathotypes were described in South Amer-
ica by Canto Saenz and De Scurrah (1977), which
was consistent with the latter being the center of
diversity for the species and only a subset of this
diversity being present in Europe. Molecular char-
acterization of
G. pallida
populations in the An-
dean region has localized the origin of European
populations to the region around Lake Titicaca in
