Genetic Modificaion of Domesticated Plants and Animals

Prof. C Kameswara Rao
Foundation for Biotechnology Awareness and Education, Bangalore, India
www.fbae.org; krao@vsnl.com, http://fbae.blogs.com/

Domestication is the art, science and technology of taming wild species of plants and animals to suit human needs, and to rear them wherever desired.   Domestication is at the root of classical agriculture and animal husbandry and was achieved through a long painstaking process.   All products of agriculture and animal husbandry we have today are the result of genetic modification of domesticated species, addressing both quality and quantity.  

The key difference between the genetic modification of wild plants and animals on one hand and of cultivated plants and animals on the other is that, wild plants evolve under the influence of natural Selection and the domesticated varieties develop under the influence of human or artificial selection.    Since many wild habitats have been interfered by man, today there is an extraneous influence on many wild species as well.   

All species of plants and animals, whether wild or domesticated, are dynamic undergoing natural changes in their gene pool, the complete set of unique alleles that would be found in every living member of that species or population.    Natural selection operates upon the naturally occurring genetic variation.  Till about a century ago, natural genetic variation was the only source of variation for crop and animal improvement by farmers and agricultural scientists.  

With rapid and ingenious technological advancements in biology and sciences related to agriculture, scientists have devised methods to experimentally induce genetic variation to create new varieties of plants and animals choosing useful traits.   Induction of gene mutation, altering chromosome number and structure, hybridization and exploitation of hybrid vigour or heterosis, have all played a crucial role in the efforts at genetic modification in classical agriculture and animal husbandry.   Nevertheless, natural genetic variation continued to be an important component of their options.  

For several reasons, the classical approach to genetic modification, based on natural and/or artificial genetic variation, was an extremely difficult process. 

a)      No matter however much advanced, the technology was imprecise.   Most of the time it was
          shooting in the dark with no control on the outcome.   
b)      Thousands of varieties had to be carefully screened to pick up one with the desired trait.  
c)      There is no control or guarantee that the gene for the chosen trait would express truly generation
          after generation. 
d)      Most mutations, natural or induced, were deleterious.  Only the scientists who worked with them
          know how many different kinds monstrosities mutation breeding has thrown up. 
e)      Like mutation breeding, altering the chromosome number or structure also produced a very
          large number of varieties among which only a few were useful.
f)        Polyploids that contained more doses of the same genes did not always mean multiplied
          advantages.
g)      The hybrids contained a lot more genes than necessary, and their function and interaction with
          other genes were unpredictable, as also is the case with mutants and polyploids.   
h)      The progeny of both natural and experimental hybrids were sterile.   This was no problem with
          vegetatively propagated crops like potato, sugarcane or grapevine, but a serious handicap with
          crops like wheat, corn, or rice, where the fruit or the seed is the economic product.

The process of human selection from this sea of variation was a tremendous and very time consuming task requiring a keen mind and eye and persistence, with no assurance of success at the end of the road, after decades of hard work.

Surmounting enormous difficulties, classical agricultural scientists and farmers have done a marvelous job in producing a couple of hundred thousand varieties of crops and animals.

There are now over 1,00,000 varieties of rice, 70,000 varieties of wheat, 15,000 varieties of beans and 12,000 varieties of potato, besides several thousand varieties of other crops.   The high yielding IR 64, one of the very popular varieties of rice, is the result of extensive hybridization involving over 160 parents in its lineage.     Repeated hybridization, with wild relatives of wheat that are resistant to the devastating wheat rust disease, produced cultivated wheat varieties resistant to the disease.  A hybrid of cultivated sugarcane (Saccharum officinarum)and its wild relative Saccharum spontaneum is resistant to the serious red rot disease.  Durum wheat, used to make pasta, is man made.   Triticale, a hybrid between wheat and rye (belonging to two different genera, Triticum and Secale)) that took 100 years to succeed, can withstand the severe winter temperatures.   Inducing mutation by irradiation, Golden Promise, a commercialized variety of barley, was produced fifty years ago.
Several thousand new varieties of garden plants, such as roses, were produced.   Such amazing feats as the production of several forms of the hybrid orchid Brassolaeliocattleya, spanning three different orchid genera, were also performed.

Similarly, classical animal husbandry produced hundreds of new breeds of farm animals, milch cattle, improved meat sources, pig, horse, dog, cat, poultry, pet birds and several others.