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Borlaug’s Methods

 

Introduction

Borlaug's Methods

Benefits of Borlaug's Wheat

Criticism of Borlaug's Wheat

References

 

 

    permission pending from Kansas State University (KSU, 2004)

 

 

 

Norman Borlaug developed his wheat strain using conventional plant breeding methods, which rely on plants’ natural  

 reproductive systems.  Wheat reproduces sexually by setting seed through self-pollination.  Conventional wheat breeding involves controlled pollinations made between two superior parent plant types.  The resulting seeds are cultivated, and the individuals in this second generation possessing the best combinations of the most desirable traits are selected for another round of controlled crosses.  This process is repeated with sebsequent generations until all progenies (lines) are genotypically and phenotypically uniform.  Once uniformity is achieved, the best lines are sown in multirow plots and compared with the best commercially available varieties for grain yield, agronomic type, disease and insect resistance, and milling and baking quality.  Trials are repeated for several years at different locations to determine the variety’s ability to react with different environments.  If a new variety significantly outperforms existing commercial strains over several years, it is eligible for commercial release (Borlaug, 1983).

 

Norman Borlaug’s initial intent in Mexico was to produce a high yield wheat variety that was also resistant to stem rust, a fungus then plaguing Latin American agriculture.  Faced with Mexico’s urgent need for a resistant wheat variety, Borlaug decided to take an unusual approach: he selected two ecological areas that would permit growth and selection of two generations of progeny each year.  With two breeding cycles every 12 months, Borlaug could develop a new variety in four years instead of the conventional eight.  The two ares Borlaug chose were separated by 10° of latitude and 2600 meters in altitude (Borlaug, 1983).  Only varieties that thrived in both environments were selected for the next rounds of controlled crosses.  This strategy resulted in high yield, rust resistant hybrids that were insensitive to climactic variations like temperature and day length.

 

Unfortunately for Borlaug, his new variety produced more grain than could be supported by tall stems; the plants “lodged,” becoming top-heavy and falling over.  Borlaug hunted for a strain with shorter, stouter stalks and finally found some dwarf varieties from Japan.  However, this Japanese wheat “produced unusable grain, was often sterile, and was so susceptible to disease that the year’s first crop was wholly lost to rust” (Mann, 1997).  Borlaug spent years crossing his resistant strain and the Japanese strain, a winter wheat variety called Norin 10, and finally released two semidwarf spring wheat varieties, Pitic 62 and Penjamo 62, in 1962; in 1964 he released four more varieties called Sonora 64, Lerma Rojo 64, Super X, and Siete Cerros (Borlaug, 1983).  These semidwarf varieties possessed a 100 percent yield advantage over the best previously available commercial varieties because they partitioned more of the total dry matter production to grain instead of height.

 

It took Borlaug nearly twenty years, but he was able to produce rust resistant, semidwarf wheat that yielded well not only in Mexico, but in environments from Canada to Argentina.  The development of these broadly adapted spring wheat varieties would have a “tremendous impact on wheat production” worldwide (Borlaug, 1983).

 


           

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Last modified 11 February 2004