American plant breeders first tackled the problem of breeding seed-propagated crops that are open-pollinated. Self-pollinated crops, such as wheat, rice, and beans, can be genetically manipulated into pure lines which breed true. But open-pollinated crops cannot be treated in this way, because the process of self-pollination produces 'inbreeding depression' in which the vigour and yield are severely reduced. Charles Darwin first observed this phenomenon in plants, in England, in 1876.

Darwin also observed the converse of inbreeding depression, which is called 'hybrid vigour' or heterosis. If two strongly inbred, and severely depressed, maize lines are crossed, the progeny exhibits hybrid vigour, and it yields about twenty percent more than the best open-pollinated maize crop. Such a progeny is called a 'hybrid variety' and the crop is known as 'hybrid corn' or 'hybrid maize'. A brief history of this development was given at 2.12.2 and need not be repeated here.

The production of hybrid corn seed led to a surge of private enterprise in maize breeding in the United States. Most companies, which grew wealthy on the proceeds of hybrid corn seed, reinvested much of this wealth in research designed to produce even better hybrids. This private enterprise prompted an entirely new idea called plant breeders' rights that was first translated into legislation in the United States in the 1930s.

Many countries now have legislation designed to protect a new crop variety, in the same way that an author's copyright protects his writing. A registered crop variety can then earn royalties, just as a book earns royalties. And a plant breeder can hope to produce a 'best seller', just as an author can hope to write a best selling book. Try to imagine the condition of world literature if there were no author's copyrights. That condition is approximately the state of modern plant breeding.

Plant breeders' rights are not necessary in hybrid varieties of open-pollinated crops. These include the open-pollinated cereals such as maize, sorghum, and millets, as well as many members of the cucumber, beet, cruciferous, and onion families. But they are very necessary in all other crops, where they are as necessary to private enterprise in plant breeding, as copyrights are to private enterprise in writing, painting, sculpting, photography, and music.

Until now, plant breeders' rights have failed to stimulate private plant breeding. But this is only because of the widespread conviction that plant breeding must be conducted by highly trained scientists working in very large and expensive institutes. With the realisation that breeding crops for horizontal resistance is both easy and rewarding, private plant breeding should escalate and, finally, the plant breeder's rights legislation will be justified.

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