Agriculture Reference
In-Depth Information
( 2010 ) incorporated an imidazolinone resistance (IR) XA17 gene into some maize
lines that confers resistance to imazaquin and nicosulfuron herbicides. These IR-
maize lines showed resistance to the Striga hermonthica weed and the yield loss
was minimized to a considerable level. The expression of bar gene responsible for
resistance to herbicides in sweet potato was demonstrated by Zang et al. ( 2009 ).
Approaches that have been used to generate herbicide-tolerant crops are: (1)
Decrease the sensitivity of the plants to the herbicide by modifying the sensitivity of
the target enzyme and (2) engineer a herbicide detoxifying pathway in to the plant
(Simoens and Van Montagu 1995 ). For instance glyphosate and acifluoren tolerance
is included in first approach. Transgenic plants tolerant to the herbicide acifluorfen,
which inhibits chlorophyll biosynthesis, have been produced through overexpres-
sion of the target enzyme involved in chlorophyll biosynthesis (Lermontova and
Grimm 2000 ; Ahmad et al. 2012 ). Second approach includes the resistance to glu-
fosinate and bromoxynil. To enhance the metabolism of these herbicides various
genes were introduced and the active compound is converted to products are non-
toxic to the crop (Haumann 1997 ; Ahmad et al. 2012 ). Now the critics of herbicide
resistant crops fear the over use of herbicides and the development of herbicide
resistant weeds. But the herbicide resistant weeds can be controlled by rotating the
crops with different transgenic modes of action. Various environmentally friendly
herbicides and their corresponding resistant genes are available that makes crop
rotation practices possible.
AbioticStress
Abiotic stress (Salinity, drought, temperature, UV Radiations etc.) has been found
to have negative impact on the crop production. The crop loss due to these abiotic
stresses is responsible for the enormous economic loss worldwide (Ahmad et al.
2008 , 2010 , 2012 ).
Conventional breeding techniques have been used to improve the crop produc-
tion but much success has not been achieved in generating stress tolerant plants.
Plant biologists have developed transgenic technology to generate stress tolerant
plants and to improve the crop production. Modification of the biochemical path-
ways through the transgenic approach and overexpression of the stress tolerant
genes have great success in achieving the target of generating stress tolerant plants.
For further information see Table 3.2 .
Conclusions and Future Perspectives
Plant tissue culture has emerged as an inescapable tool with possibilities for comple-
menting the conventional methods in plant breeding and crop improvement. These
techniques have proved successful and are now being used globally for the ex-situ
conservation of the plants including crop plants. Plant cell/tissue culture is a rapidly
Search WWH ::




Custom Search