Agriculture Reference
In-Depth Information
10
Plant Parasitic Nematodes
of Potato
Juan E. Palomares-Rius,
1,
2
* Claudio M.G. Oliveira
3
and Vivian C. Blok
2
1
Institute for Sustainable Agriculture (IAS), Spanish National Research Council
(CSIC), Córdoba, Spain;
2
Cell and Molecular Sciences, James Hutton Institute,
Invergowrie, UK;
3
Instituto Biológico, Campinas, Brazil
The Phylum Nematoda is highly diverse in terms
of species richness and is one of the most abun-
dant metazoan groups on Earth (Hugot
et al
.,
2001). Nematodes are essentially aquatic organ-
isms, the majority of which are microscopic in
size (0.3-3.0 mm), found in habitats ranging
from oceans to the microscopic film of water sur-
rounding soil particles (De Ley, 2000). Based on
their different feeding habits, terrestrial nema-
todes can be divided into functional (trophic)
groups (Yeates
et al
., 1993). The plant parasitic
nematode (PPN) group is regarded as one of the
most important due to the direct damage they
cause to crops, the indirect damage resulting from
subsequent fungal and bacterial infection, and for
some species the transmission of plant viruses.
Other non-parasitic, free-living nematode species
are also of great economic importance in agricul-
tural systems due to their involvement in nutrient
cycling and maintaining soil health.
Global annual crop losses from PPNs due to
reduced yield and quality, and additional man-
agement costs, have been estimated at approxi-
mately 12% (Chitwood, 2003), corresponding
to monetary losses to world agriculture of ap-
proximately US$100 billion. The lack of specific
diagnostic symptoms resulting from PPN infest-
ations, difficulties in effective sampling (PPNs
typically have patchy distributions within the
field and can be highly dispersed within the soil
profile), the occurrence of PPNs as mixtures of
species, and their microscopic size with limited
morphological features for species identification
makes determining economic damage from spe-
cific PPNs difficult. Lack of nematological ex-
pertise and resources can also be a significant
constraint in assessing the impact of nematode
problems. Eradication of PPNs, once established,
is costly and hard to achieve due to their distri-
bution within the soil matrix, the persistence of
some species in dormant stages, and the incom-
plete effectiveness of control methods such as
nematicides. Effective measures to prevent new
introductions are therefore paramount.
Aboveground symptoms are generally non-
specific and may involve stunted plant growth,
yellowing, wilting, and occasionally plant death.
Infestations can also occur with no aboveground
symptoms, but yields are reduced and/or tuber
quality is affected. The PPNs that are regarded
globally as most important in potato production
are
Globodera
spp.,
Meloidogyne
spp.,
Naccobus
aberrans
(Thorne, 1935) Thorne & Allen,
Praty-
lenchus
spp. and
Trichodorus
spp. (Nicol
et al
.,
2011). Regionally, particular species predomin-
ate, reflecting agronomic practices, climatic con-
ditions, and historical distributions/introductions.
For example,
Globodera pallida
(Stone, 1973) Behrens,
1975, was recognized in 2006 for the first time in
Idaho, USA (Skantar
et al
., 2007), and
Scutellonema
