Plant Breeding: Its Contribution to Durable Disease Control
Disease-resistant plant varieties are one of the two main pillars of crop protection, along with pesticides. Current developments in European Union legislation on the marketing and use of pesticides will increase the importance of plant breeding in disease control, but it is most unlikely that varietal resistance will ever make pesticides obsolete. Plant breeding has been one of the most revolutionary technologies of the last century, both increasing and stabilising food production despite the often unpredictable challenges posed by the natural world, including pests and diseases. The Green Revolution, which has secured the livelihoods of many millions of people in developing countries, began in the 1940s when Norman Borlaug and colleagues at CIMMYT, the International Maize and Wheat Improvement Centre in Mexico, introduced the Sr2 gene for resistance to stem rust (Puccinia graminis) into wheat varieties. In most crops, a new variety starts life as a seed from a cross between two parental varieties. Large breeding programmes make many such crosses and produce very many progeny lines each year, tens or even hundreds of thousands of progeny in an important crop such as wheat. These lines are grown in a series of field trials, with breeders selecting lines from one year?s trials to sow the following year, gradually whittling down their number over successive years. Different traits are tested each year. Those that are easy and cheap to score are generally scored in early generations when there are many lines in a breeder?s nursery, while more demanding traits may be scored in later generations. Powdery mildew resistance, for example, is often selected early because it is easy to recognise and can be scored accurately in small plots. Breeding is not a quick process; for winter cereals, it takes around seven years from making the initial cross to submitting an elite selection to two further years of official trials for the National List of approved varieties. In the UK, levy boards run further trials of some crops, including cereals, oilseed rape and pulses, to produce Recommended Lists of the best varieties for farmers and end-users. The final trial is in the marketplace: of the millions of lines produced by breeders each year, a very small fraction become commercially successful varieties and are grown on a significant area.
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Document Type: Research Article
Publication date: 2011-06-01
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