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observations GkI Shull's experiments in 1907 gave an ilnpstus for plant breeding that
resulted III an exponential Increase in brcedlng programs, which w~s in turn expanded to
countless nlembers of cultivable variet~es. Socio-eco~lomic Importance of these progranla
gave birth to thousands of varieties initially In cereals and later in otl~rr dol~~esticated
crops. However, breeding is a highly t~~r~c consuming process and labor intensive as the
crossing means polll~lat~ng every plant mailually. Crops wit11 lo~lg duration life cycles pose
variety oT problcms in co~~ve~ltio~lal breeding. Another I~~liltat~o~l 01' the cunventio~i:~l
breed~ng lies in the susu;~l ~ncompatib~lity of the cultivated varieties with their wild
relatives, where the ancestral wild varieties were proven to tie the reservoirs of several
agronomically important traits. Tools of modern biotechtlology have come to the rescue for
some of the difficult constraints to crop improvelncnt by understand~ng their molecul;ir
basis and providing ren~edles at the n~olec~~lar level itself. ldc~lt~ficalio~l of physical basis
of life and niolzcul.ir cl~;iractcri~atlo~~ of i~ll~critn~~ce pattenls ~nads brecd~ng a more
syste~llatic and mcani~~gfui science of crop improvement. Stat~stical appropriat~on ot
polymorphisms ttlllcrlri'd with the help of techn~qucs l~lte Southern blott~ng and
polymerase chn111 reaction (PCII) gavc birth to a new faculty of'rnode1i1 agriculture that is,
marker assistcd selection (MAS). This was not only uscful ill identificat~on of quantitat~ve
tra~t loc~ (QTLs) but also uscful III isolation of gencs for a specific trait. ldentificat~on and
isolation of agronomically important gencs fro111 different prokejotes and eukaryotes
ignited a desperate wisl~ ill sc~entists to ~ntroducr: Illem into plants and observe tiieir effect
In the new env~ronnie~lt. Tile existing bacterial transformation systems (Mandel and Higa,
1970) gave some logistic support to this idea ofplant transgenes~s by recombination events
in the genetic material. Discovery of the ab~l~ly of a crown gall induc~ng soil bacterium,
.4grobacfrriton f~rr~~ejiiciert~ to introduce the genetic material Into the plants (Drummond,
1979), in late 70s revolutionized the genetic transfurn~ation research. Agrobacteriurn