Plant breeding started with sedentary agriculture and particularly the domestication of the first agricultural plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially early human farmers simply selected food plants with particular desirable characteristics, and used these as a seed source for subsequent generations, resulting in an accumulation of characteristics over time. In time however experiments began with deliberate hybridization, the science and understanding of which was greatly enhanced centuries later by the work of Gregor Mendel. Mendel's work ultimately led to the new science of genetics. Modern plant breeding is applied genetics, but its scientific basis is broader, covering molecular biology, cytology, systematics, physiology, pathology, entomology, chemistry, and statistics (biometrics). It has also developed its own technology.
Plant breeding efforts may be divided into different historical landmarks:
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Plant breeding in certain situations may lead to the domestication of wild plants. Domestication of plants is an artificial selection process conducted by humans to produce plants that have more desirable traits than wild plants, and which renders them dependent on artificial (usually enhanced) environments for their continued existence. The practice is estimated to date back 9,000-11,000 years. Many crops in present day cultivation are the result of domestication in ancient times, about 5,000 years ago in the Old World and 3,000 years ago in the New World. In the Neolithic period, domestication took a minimum of 1,000 years and a maximum of 7,000 years. Today, all of our principal food crops come from domesticated varieties. Almost all the domesticated plants used today for food and agriculture were domesticated in the centers of origin. In these centers there is still a great diversity of closely related wild plants, so-called crop wild relatives, that can also be used for improving modern cultivars by plant breeding.
A plant whose origin or selection is due primarily to intentional human activity is called a cultigen, and a cultivated crop species that has evolved from wild populations due to selective pressures from traditional farmers is called a landrace. Landraces, which can be the result of natural forces or domestication, are plants (or animals) that are ideally suited to a particular region or environment. An example are the landraces of rice, Oryza sativa subspecies indica, which was developed in South Asia, and Oryza sativa subspecies japonica, which was developed in China.
For more on the mechanisms of domestication, see Hybrid (biology).
There were some experiments before Mendel on hybridization and selection. Some seed companies such as Gartons Agricultural Plant Breeders in England were also established based on success on these methods. Another part discovery of North America by Columbus in 1492 triggered unprecedented transfer of plant resources, first from old world to the new world, or the New World to the old. This increased variability in total genetic resources.
Gregor Mendel's Mendel's experiments with plant hybridization led to his establishing laws of inheritance. Once this work became well known, it formed the basis of the new science of genetics, which stimulated research by many plant scientists dedicated to improving crop production through plant breeding.
During the 20th century there was remarkable improvement in three economically important crops that made the food deficit world into a food surplus world. This is called the green revolution. The first, development of hybrid maize, the second development of high yielding and input responsive “semi-dwarf wheat” (CIMMYT breeder N.E. Borlaug received Nobel prize for peace in 1970), the third is high yielding “short statured rice” cultivars.[1] Similarly, remarkable improvements were achieved in other crops like sorghum and alfalfa.
Totipotency shown by plants gave rise to tissue culture techniques such as somatic hybridization, doubled haploid production, clonal propagation, and in-vitro selection. Intensive research in molecular genetics has led to development of recombinant DNA technology (popularly called Genetic Engineering). Advancement in Biotechnological techniques has opened many possibilities for breeding crops. Thus mendelian genetics allowed plant breeders to perform some genetic transformation in few crops, molecular genetics provides key not only the manipulation of the internal structure but also their “crafting” according to plan.