Agriculture Reference
In-Depth Information
Donal in somatic hybridization (Brown
et al
.,
1996);
Solanum hougasii
Correll against race
1
and race
2
of
M. chitwoodi
and
M. fallax
(Brown
et al
., 1999);
Solanum stoloniferum
Schltdl. &
Bouché and
Solanum fendleri
Schltdl. & Bouché,
both resistant to
M. fallax
and
M. chitwoodi
(Jans-
sen
et al
., 1997);
Solanum chacoense
Bitter against
M. fallax
and
M. hapla
;
S. tarijense
against
M. hapla
(Draaistra, 2006); and
S. sparsipilum
against
M. fallax
(Abou Bakari
et al
., 2006). However,
the combining of resistance genes from
S. tarijense
and
S. chacoense
does not result in an increase of
resistance against
M. hapla
(Tan
et al
., 2009).
Some clones of
S. chacoense
and
S. tuberosum
have been found to be resistant to Italian popula-
tions of
Meloidogyne arenaria
,
M. hapla
,
M. incog-
nita
, and
M. javanica
(Di Vito
et al
., 2003), opening
the possibility of breeding for resistance to more
tropical species.
Resistances for other nematode species
have been studied less intensively. Several native
S. tuberosum
ssp.
andigena
with resistance have
been identified (ex. Andean landraces Azul, Hua-
ca Lajra, and Tunti Imilla), as well as resistant
wild tuber-bearing
Solanum
species (
Solanum
megistracrolobum
Bitter,
Solanum acaule
Bitter,
and
S. sparsipilum
) against
N. aberrans
(Cahuana
et al
., 1975; Inserra
et al
., 1985; Suarez
et al
.,
2009). However, resistance seems to be depend-
ent on the race and/or population. Other nema-
todes such as
Pratylenchus
spp. or
D. destructor
have presented fewer possibilities with resistance
or tolerant cultivars.
PCN eggs (Clovis and Nolan, 1983), and up to 93%
infection of eggs has been achieved in laboratory
experiments with
Verticillium suchlasporium
Gams & Dackman (Dackman, 1990).
Beauveria
brogniartii
(Sacc.) Petch showed good control in
laboratory and greenhouse experiments against
N. aberrans
on potatoes (Balderrama, 1992).
Transgenic potatoes
Several transgenic clones have been produced,
and they represent a new prospect for nematode
management. One has used the expression of a
proteinase inhibitor against a broad spectrum of
nematodes. Transgenic plants derived from com-
mercial cultivars have been tested against
G. pallida
and
M. incognita
, including localizing expression
using root-specific promoters (Lilley
et al
., 2004).
The combination of natural R genes and cysta-
tin genes in the commercial cultivars Sante and
Maria Haunca produced high levels of resist-
ance to virulent and avirulent populations of
G. pallida
in Sante (Urwin
et al
., 2003). Cystatin-
expressing potato plants do not harm non-target
insect aerial feeders, their natural parasitoid
enemies, or the soil microbial community (Fuller
et al
., 2008). In the future, as more information
about natural plant proteinase inhibitors and
their possible nematode targets increases with
better designs of synthetic proteinase inhibitors,
the efficiency of these techniques may improve
even further.
Another transgenic plant strategy is the ex-
pression
in planta
of double-stranded RNA (dsRNA),
which can interfere with the gene expression of
the targeted nematode gene following its inges-
tion. Transgenic potatoes using this technology
are not yet well developed, but several potential
genes for silencing have been studied in some of
the major PPNs of potato, as well as with model
plants (Lilley
et al
., 2007). Recently, other ap-
proaches using nematode-repellent peptides
have been developed in potato (Lilley
et al
.,
2011), and this interesting technique has also
been implemented using specific expression in
the cells of the root cap with the promoter AtM-
DK4-
20.
Resistance levels of 95% were achieved
against
G. pallida
using these transgenic plants.
The combination of high efficiency in PPN con-
trol combined with specific expression using pro-
moters makes these plants interesting for future
field applications.
New management strategies
Biocontrol agents
Not many biocontrol agents have been devel-
oped for potato. However, as more nematicides
will be withdrawn from the market, new possi-
bilities for these agents to be incorporated are
being considered. Several agents look promising
against some PPNs.
Paecilomyces lilacinus
(Thom) Samson and
Pochonia chlamydosporia
(Goddard) Zare & W. Gams have offered good re-
sults against PCNs (Jacobs
et al
., 2003; Tobin
et al
.,
2008). For these organisms, more research with
different environmental conditions will help to
determine their potential for use as part of an
IPM strategy. Other fungi have been isolated from
