The Success of Modern Agriculture

The twentieth century increase in agricultural production comes mainly from:

  • An increased area of cultivation, by putting more land under the plough.
  • Irrigation, often to the grave detriment of aquifers.
  • Mechanisation, such as the use of tractors, and of other machines such as combine harvesters for cereals, pulses, oilseeds, and mustard.
  • Chemicals, such as artificial fertilisers, herbicides, and crop protection chemicals.
  • The contribution made by plant breeders, which comes manly from an increased yield potential that can utilise these new techniques.

There have been some major breeding successes, particularly in the following crops.

2.12.1 Sugar beet

The improvement in both the yield and the sucrose content of fodder beet occurred mostly during the nineteenth century. It was stimulated originally by the Napoleonic wars, when continental Europe was blockaded by Britain, and cane sugar from the West Indies was unavailable. These improvements, which continued during the twentieth century, produced the entirely new crop known as sugar beet. This breeding involved the quantitatively inherited characters of both sucrose content and root yield, and they were improved by recurrent mass selection and transgressive segregation. The sucrose content, for example, was increased from 4% in the original fodder beet to over 20% in modern sugar beet cultivars.

2.12.2 Hybrid maize

In 1918, Donald F. Jones invented the 'double hybrid' method of producing hybrid maize seed. He produced a cross of two single crosses, using a total of four inbred lines. His double hybrid is usually represented as (A x B) x (C x D). It produced a hybrid variety that was uniform, and which yielded 20% more than the best open-pollinated maize. This double hybrid method permitted the production of hybrid maize seed in commercial quantities, and it resulted in one of the most productive advances in the entire history of agriculture in the United States. Within fifteen years of Jones' discovery, double hybrid maize was economically important and, by 1950, virtually all the corn of the corn belt was planted to double hybrids. By 1970, most commercial maize crops throughout the industrial world were double hybrids, and the technique was becoming increasingly important in non-industrial countries.

The double hybrid maize had a secondary effect on plant breeding that was both profound and important. The progeny of a hybrid variety do not possess any hybrid vigour, and they revert to the lower yields of open-pollinated maize. This means that new hybrid seed must be purchased for each new crop. This protects a plant breeder, who produces a new and superior hybrid variety, from unlawful commercial competition. No unauthorised person can produce seed of that hybrid, because only the breeder possesses the original inbred lines that produce the double hybrid.

The production of hybrid corn seed led to a surge of private enterprise in maize breeding in the United States. Many companies, which grew wealthy on the proceeds of hybrid corn seed, re-invested much of this wealth in research. This private enterprise prompted an entirely new idea called 'plant breeders' rights' that is highly relevant to this book (see 11.20).

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 strive to produce a 'best seller', just as an author can strive to write a best selling book.

Plant breeders' rights are not necessary in hybrid varieties of open-pollinated crops, such as maize, cucumbers, water melons, sunflowers, and onions, because the hybrid vigour is lost in the next generation. But they are very necessary in all other crops, where they are as essential to private enterprise in plant breeding, as copyrights are to private enterprise in writing, painting, sculpting, photography, and music.

2.12.3 Soybean

Soybean is very sensitive to day-length and, additionally, the older varieties were both low yielding and unsuitable for mechanical harvesting. Breeding in the United States solved these problems and was so successful that soybean began to rival maize as the most important crop in this country. The crop has been important in the orient for millennia, but it became important on the West only with new breeding, and with new industrial processes. Soybean now has an essentially industrial function, and is grown for processing in factories. It is a crop of major importance in various countries, with Brazil and China being among the largest producers, and it is now the most important grain legume in the world.

2.12.4 Sugarcane

Late in the nineteenth century, it was discovered that sugarcane could be propagated from true seed, and very successful breeding stations were soon operating in about a dozen different countries. Many dramatic improvements in yield and resistance to parasites were obtained and this very successful breeding has even been dubbed 'the first green revolution'. Interestingly, all the breeding involved pedigree breeding techniques, even though no single-gene characters are known in this crop. This anomaly was recognised by the breeders in Hawaii who started a recurrent mass selection program which they called the 'melting pot technique', and which quickly proved to be the most successful cane breeding of all (see 7.20.3).

2.12.5 Dwarf wheats and rices

The development of the dwarf wheats and rices of the 'Green Revolution' was one of the most important agricultural advances of the twentieth century, second only to the development of hybrid maize. It changed some of the most densely populated countries of the world from being grain importers into being grain exporters. These so-called 'miracle' varieties, otherwise known as dwarf varieties, had the character of short straw. This character is genetically controlled by major genes, and it permitted high levels of nitrogenous fertilisation, and considerably improved yields, without risk of lodging. Unfortunately, these improvements were produced by pedigree breeding and, as a consequence, these cultivars have ephemeral resistances to many of their parasites.

They are typical of the "big space, high profile, high cost, few cultivars, short life" characteristics of vertical resistance (see 5.6).

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