Agriculture Reference
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and Bt toxins in transgenic crops can be used to fight insect resistance. US based
company Monsanto with India's Maharastra Hybrid Seeds Company (Mahyco) has
recently developed a Bt eggplant (  Solanum melongena ) by incorporating a crystal
gene (Cry1Ac) from B. thuringiensis (Krattiger 2010 ; Cotter 2011 ).
DiseaseResistance
Diseases caused by bacteria, fungi, viruses and nematodes are responsible for dam-
aging the crop plants, i.e phytopathogens have been threatening human life through
the loss of crop production. For example the production of potato has been threat-
ened by several fungal diseases and microbial pathogens resulting in 20 % yield
loss (Walter et al. 2011 ). Even though in potato the Botrytis cinerea is not the main
disease, it may cause other serious diseases like Fusarium solani and Phytophthora
infestans . But the transgenic approaches have used the genes encoding pathogenesis
related (PR) proteins that confer the resistance to fungal pathogens (Hoshikawa
et al. 2012 ; Gao et al. 2000 ) (Table 3.1 ). These PR proteins have antimicrobial
properties against many fungal and bacterial pathogens. Transgenic approaches pro-
vide a powerful tool for the development of disease resistant crops (Melchers and
Stuiver 2000 ; Rommens and Kishor 2000 ; Ellis et al. 2000 ). One approach involves
the viral gene expression that interferes with the completion of life cycle of viruses.
Powell-Abel et al. 1986 discovered that the coat proteins for TMV (tobacco mosaic
virus) expressed in host plant interfered with the replication and plants expressing
the TMV coat protein gene were resistant to TMV infection. This approach is now
widely used to protect the crops from a large number of viruses (Mundembe et al.
2009 ). In 1992, china was the first country to commercialize these virus resistant
transgenic crops (Brookes and Barfoot 2012 ; James 1997 ). After this virus-resis-
tant tomato, squash and watermelon plants were also produced (Meeusen 1996 ).
In oilseed rape, overexpression of tomato chitinase gene with a strong promoter
gene has resulted increased resistance fungal attack in plants (i.e pathogens such as
Cylindrosporium concentricum and Phoma lingam) (Grison et al. 1996 ). Anand
et al. ( 2003 ) reported that wheat plants co-expressing a chitinase and β-1, 3-glu-
canase genes obtained to Fusarium graminearum . And under the green house and
field conditions, transgenic potato plants expressing alfalfa antifungal peptide (al-
fAEP) showed strong defense activity against fungal pathogen, Verticillium dahliae
(Gao et al. 2000 ). Thionins (PR proteins) are toxic to phytopathogens by attacking
the cell membrane to increase their permeability and cause the death of the fungal
cell due to leakage of proteins, nucleotides and other components (Chan et al. 2005 ;
Hoshikawa et al. 2012 ). For example, overexpressed gamma-thionin gene from
wasabi (  Eutrema wasabi ) in transgenic rice enhanced resistance to rice blast disease
caused by Magnaporthe grisea (Kanzaki et al. 2002 ). Even in transgenic potato
plants, potato thionin (snaking-1) gene expressed enhanced resistance to Rhizocto-
nia solani and Erwinia cartovora (Almasia et al. 2008 ). The wasabi thionin gene in
transgenic potato plants had antifungal activity against gray mold (  Botrytis cinerea )
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