Agriculture Reference
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has been reported for rice (Christou et al. 1991 ), maize (Gordon-Kamm et al. 1990 ),
wheat (Weeks et al. 1993 ), oat (Somers et al. 1992 ), rye (Castillo et al. 1994 ), barley
(Harwood et al. 1995 ; Hagio et al. 1995 ; Kihara et al. 1998 ; Shim and Kasha 2003 ).
Using isolated microspore as explants, the first homozygous transgenic Indica rice
was reported by Datta et al. ( 1990 ).
Plant genetic engineering also holds the promise of circumventing the problems
faced in wide hybridization programs, especially when sources of resistance are not
available in taxonomically related species (Davey et al. 2010 ). Increasing research
efforts through genetic engineering for abiotic stress tolerance in crops, are being
employed (Holmberg and Bülow 1998 ; Umezawa et al. 2006 ). Certain genes are
expressed at elevated levels when a plant encounters stress (Bray 1993 ). A cis-
acting dehydration responsive element (DRE), identified in Arabidopsis thaliana ,
is involved in ABA-independent gene expression under drought, low temperature,
and high salt stress conditions in many dehydration responsive genes (Nordin et al.
1991 ; Yamaguchi-Shinozaki and Shinozaki 2007 ; Iwasaki et al. 1997 ). It is gener-
ally agreed that in order to meet future challenges in food production, multi-disci-
plinary, multi-faceted approaches are needed. Solutions to the problem of how the
developing world will meet its future food needs, are broader than producing more
food, although the successes of the 'Green Revolution' demonstrate the importance
of technology in generating the growth in food output in the past. Despite these
successes, the world still faces continuing vulnerability to food shortages. It seems
likely that conventional crop breeding, as well as emerging technologies based on
molecular biology, genetic engineering and natural resource management, will con-
tinue to improve productivity in the coming decades (Huang et al. 2002 ). The use
of genetic engineering technology could lead to simpler and more effective gene-
based approaches for improving crop tolerance. Transcription factors have been
shown to produce multiple phenotypic alterations, many of which are involved in
stress responses.
2.2.7   Major Abiotic Stress Factors under Androgenesis and Combined  
with Genetic Engineering Research
The main targets for genetic engineering include modification of plants to enhance
their tolerance to biotic stresses (herbicides used to control weeds and to confer
resistance to insects, bacteria, fungi, and viruses). Baisakh et al. ( 2001 ) obtained
homozygous transgenics in about a year from the start of transformation till the con-
firmation of the anther-derived line versus a minimum of 20-24 months required
in the usual course of generation advancement. Very recently, Roy et al. ( 2011 )
reported that employing transgenic technology, functional validation of various tar-
get genes involve in diverse processes, such as signaling, transcription, ion homeo-
stasis, antioxidant defense etc. to enhance abiotic stress tolerance crop plants. To
date, different abiotic stresses to crop improvement are shown in Table 9.1 . Crop
improvement in some cereals using androgenesis and genetic transformation meth-
ods is shown in Table 9.2 .
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