Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 64

The term “breeder” is a modern‐day reference to professionals who knowingly manipulate the nature of plants to improve their appearance and performance in predetermined ways. These professionals operate with formal knowledge from the discipline of plant biology and allied disciplines. They are preceded by people who unknowingly and indirectly manipulated the nature of plants to their advantage. This category of “breeders” (to use the term very loosely), or “farmer‐breeders,” continues to impact world crop production today. Of course, the image of the farmer today is variable from one part of the world to another. In developing countries, many farmers still produce crops with primitive technologies, while high‐tech defines the farmer of today in technologically advanced countries.

The age‐old practice is for farmers to save seed from the current year's crop to plant the next season's crop. In doing so, farmers depend on their instincts, intuition, experience, and keen observation to save seed from selected plants for planting the next crop. Performance and appeal are two key factors in the decision making process. For example, seeds from a plant without blemish among a plot of others with disease symptoms would be saved because it obviously had “something” that makes it ward off diseases. This may be described as primitive or rudimentary “breeding” for disease resistance. Similarly, farmers may save seed on the basis of other agronomic features of their preference, such as seed or fruit size, seed or fruit color, plant stature, and maturity, and in the process manipulate plant genetics without knowing it. I call this “unconscious breeding.”

Over time, farmers create varieties of crops that are adapted to their cultural environments, the sole technique being the art of discrimination among variability, or selection as it is called in modern crop improvement. These creations are called farmer‐selected varieties and sometimes landraces. The practice prevails in areas of subsistence agriculture, which represent many parts of the developing world. These varieties are highly adapted to local regions and can be depended upon by farmers who produce their crops with limited resources. Farmer‐selected seed continues to sustain agricultural production in these parts of the world while the commercial seed supply system is being developed.

Farmer‐selected varieties or landraces are an important source of breeding material for modern breeders. This primitive or exotic germplasm is heterogeneous and is useful for initiating some plant breeding programs.