Impacts on Nematode Pests - Climate Resilient Agriculture for Ensuring Food Security - page 186

achieving durable, broad-spectrum nematode
resistance (Thomas and Cottage 2006 ). A number
of genes that mediate nematode resistance have
now been or soon will be cloned from a variety of
plant species. Nematode resistance genes are
present in several crop species and are an impor-
tant component of many breeding programs
including those for tomato, potato, soybeans, and
cereals (Trudgill 1991 ). There are essentially
three approaches for engineering resistance:
transgenic expression of natural resistance genes
in heterologous species, targeting and disruption
of the nematode, and feeding site attenuation
(Thomas and Cottage 2006 ).
Using marker-assisted breeding techniques,
Monsanto is introducing root-knot nematode
resistance into elite genetics to develop cotton
varieties that could potentially increase lint yield
by an average of 8-10 % under root-knot nema-
tode infestations.
A new, high-throughput screening method is
being utilized to accelerate the incorporation of
reniform nematode resistance into elite genetics
of cotton. The product could potentially increase
lint yield by an average of 10-15 % under reni-
form nematode infestation conditions.
Pineapple plants transformed with the modi-
fi ed rice cystatin gene (proteinase inhibitor)
have tested positive for transgene expression,
particularly in the root tissue. Cystatin has been
shown to deter reniform nematode feeding and
reduce populations by interfering with their
ability to produce digestive enzymes (Atkinson
et al. 1996 ). The planting of the reniform
nematode-resistant pineapple is assumed to
replace the current use of fumigants and nemati-
cides in Hawaiian pineapple. This reduction
totals to 1.4 million pounds per year in active
ingredient with an associated savings of
$2.1 million in expenditures.
Potato plants were developed that transgeni-
cally expressed a disulfi de-constrained peptide
(nAChRbp) capable of binding to nematode acetyl-
choline receptors and inhibiting chemoreception of
cyst nematodes. The results validate the root tip-
specifi c promoter of the Arabidopsis MDK4-20
gene (Lilley et al. 2010 ) as a means of delivering
effective root protection from Globodera pallida
by the peptide under fi eld conditions.

When susceptible sugar beet genotypes are
co-transformed with Agrobacterium rhizogenes
to introduce the (Hs1.sup.pro-1) resistance gene,
the hairy roots formed exhibit resistance to sugar
beet cyst nematode (Cai et al. 1997 ). It was
reported that the nematode population decreased
by 73 % with experimental resistant varieties
whereas that increased by 35 % with a suscepti-
ble variety (Werner et al. 1995 ). A resistant vari-
ety called Nematop was developed which showed
acceptable performance in nematode-infested
soil (Dewar 2005 ).
For the fi rst time, it has been shown that a Bt
Cry6A protein can confer plant resistance to an
endoparasitic nematode ( Meloidogyne incognita )
and that Cry 6A proteins have the potential to
control plant-parasitic nematodes in transgenic
tomato plants (Xiang-Qian et al. 2007 ).
The Mi gene (true R gene) from tomato con-
ferred resistance against a root-knot nematode
and an aphid in transgenic potato (Rossi et al.
1998 ).
In the transgenic tobacco plants, AtNPR1 high
expression line 19-1 recorded the highest shoot
and root weight, which is about fi vefold higher,
compared to the wild-type plants. The number of
root galls and egg masses developed on the
infected roots of the transgenic plants was signifi -
cantly less (up to 50-60 % less) compared to the
wild-type plants (Bhanu Priya et al. 2011 ).
Tobacco plants were engineered to produce
dsRNA of two essential genes of the parasitic nem-
atode M. incognita . The transgenic tobacco plants
very effectively resisted M. incognita infection,
and their development was severely impaired.
These nematodes were specifi cally defi cient in the
mRNA of targeted genes, indicating that the
dsRNA produced in plants did indeed trigger RNAi
response in the nematode (Yadav et al. 2006 ).

9.9 Conclusions

Research on impact of climate change on soil
nematodes has been limited, with most work con-
centrating on the effects of a single atmospheric
constituent under controlled conditions. A few
recent experiments have also reported the