Norman Borlaug

Norman Ernest Borlaug (born 25 March 1914) is an American agricultural scientist, humanitarian, Nobel laureate, and the father of the Green Revolution. Borlaug received his Ph.D. in plant pathology and genetics from the University of Minnesota in 1942. He took up an agricultural research position in Mexico, where he developed semi-dwarf high-yield, disease-resistant wheat varieties.

Wheat research in Mexico

The Cooperative Wheat Research Production Program, a joint venture by the Rockefeller Foundation and the Mexican Ministry of Agriculture, involved research in genetics, plant breeding, plant pathology, entomology, agronomy, soil science, and cereal technology. The goal of the project was to boost wheat production in Mexico, which at the time was importing a large portion of its grain. George Harrar, a plant pathologist, recruited and assembled the wheat research team in late 1944. The three other members were Edward Wellhausen, maize breeder, John Niederhauser, potato breeder, and Norman Borlaug, all from the United States.{{mn|science1970|8}} Borlaug would remain with the project for 16 years. During this time, he bred a remarkably successful high-yield, disease-resistant, semi-dwarf wheat.

Related Topics:
Rockefeller Foundation - Genetics - Plant breeding - Entomology - Agronomy - Soil science - Cereal - Edward Wellhausen - John Niederhauser - Wheat

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Borlaug said that his first couple of years in Mexico were difficult. He lacked trained scientists and equipment. Native farmers were hostile toward the wheat program because of serious crop losses from 1939 to 1941 due to stem rust. "It often appeared to me that I had made a dreadful mistake in accepting the position in Mexico," he wrote in the epilogue to his book, Norman Borlaug on World Hunger.{{mn|greengiant|6}} He spent the first 10 years breeding wheat cultivars resistant to disease, including rust. In that time, his group made 6,000 individual crossings of wheat.{{mn|UoMMexico|9}}

Related Topics:
1939 - 1941 - Rust

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Double wheat season

His work had initially been concentrated in the central highlands, in the village of Chapingo near Texcoco, where the problems with rust and poor soil were most prevalent. He realized, however, that he could speed up breeding by taking advantage of the country's two growing seasons. In the summer he would breed wheat in the central highlands as usual, but then immediately take the seeds north to the Yaqui Valley research station near Ciudad Obregón, Sonora. The difference in altitudes and temperatures would allow more crops to be grown each year. His boss, George Harrar, was against this expansion. Besides the extra costs that would be incurred from doubling the work, Borlaug's plan went against a then-held principle of agronomy that has since been disproved. It was believed that seeds needed a rest period after harvesting, in order to store energy for germination before being planted, whereas Borlaug's new plan left no time between harvest and planting. Harrar vetoed his plan, causing Borlaug to resign. Elvin Stakman, who was visiting the project, calmed the situation, talking Borlaug into withdrawing his resignation and Harrar into allowing the double wheat season. As of 1945, wheat would then be bred at locations 700 miles (1000 km) apart, 10 degrees apart in latitude, and 8500 feet (2600 m) apart in altitude. This was called "shuttle breeding".

Related Topics:
Chapingo - Texcoco - Summer - Yaqui Valley - Ciudad Obregón - Sonora

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As an unexpected benefit of the double wheat season, the new breeds didn't have problems with photoperiodism. Normally, wheat varieties can't adapt to new environments, due to the changing periods of sunlight. "As it worked out," Borlaug later recalled, "in the north, we were planting when the days were getting shorter, at low elevation and high temperature. Then we'd take the seed from the best plants south and plant it at high elevation, when days were getting longer and there was lots of rain. Soon we had varieties that fit the whole range of conditions. That wasn't supposed to happen by the books".{{mn|UoMMexico|9}} This meant that the project wouldn't need to start separate breeding programs for each geographic region of the planet.

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Increasing disease resistance through multiline varieties

Because pureline (genotypically identical) plant varieties often only have one or a few major genesfor disease resistance, and plant diseases such as rust are continuously producing new races that can overcome a pureline's resistance, multiline varieties were developed. Multiline varieties are mixtures of several phenotypically-similar purelines which each have different genes for disease resistance. By having similar heights, flowering and maturity dates, seed colors, and agronomic characteristics, they remain compatible with each other, and don't reduce yields when grown together on the field.

Related Topics:
Genotypically - Genes - Disease - Phenotypically

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In 1953, Borlaug extended this technique by suggesting that several purelines with different resistance genes should be developed through backcross methods using one recurrent parent.{{mn|Borlaug1953|10}} Backcrossing involves crossing a hybrid and subsequent generations with a recurrent parent. As a result, the genotype of the backcrossed progeny becomes increasingly similar to that of the recurrent parent. Borlaug's method would allow the various different disease-resistant genes from several donor parents to be transferred into a single recurrent parent. To make sure each line has different resistant genes, each donor parent is used in a separate backcross program. Between five and ten of these lines may then be mixed depending upon the races of pathogen present in the region. As this process is repeated, some lines will become susceptible to the pathogen. These lines can easily be replaced with new resistant lines. As new sources of resistance become available, new lines are developed. In this way, the loss of crops is kept to a minimum, because only one or a few lines become susceptible to a pathogen within a given season, and all other crops are unaffected by the disease. Because the disease would spread more slowly than if the entire population were susceptible, this also reduces the damage to susceptible lines. There is still the possibility that a new race of pathogen will develop to which all lines are susceptible, however.{{mn|tnau|11}}

Related Topics:
1953 - Pathogen

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Dwarfing

To significantly increase yield in nutrient-poor soil, Borlaug needed to use fertilizer. However, the cultivars he was working with had tall, thin stalks. Taller wheat grasses could better compete for sunlight, but tended to collapse under the weight of the extra grain—a trait called lodging—and from the rapid growth spurts induced by nitrogen fertilizer. To prevent this, he bred his wheat to favor shorter, stronger stalks that could better support larger seed heads. In 1953, he acquired a Japanese dwarf variety of wheat called Norin 10 that had been crossed with a high yielding American cultivar called Brevor 14.{{mn|Reitz1970|12}} Dwarfing is an important agronomic quality for wheat; dwarf plants produce thick stems and do not lodge. Norin 10/Brevor is semi-dwarf (one-half to two-thirds the height of standard varieties) and produces more stalks and thus more heads of grain per plant. Also, larger amounts of assimilate were partitioned into the actual grains, further increasing the yield. Borlaug crossbred the semi-dwarf Norin 10/Brevor cultivar with his disease-resistant cultivars to produce wheat varieties that were adapted to tropical and sub-tropical climates.{{mn|Hedden|13}}

Related Topics:
Fertilizer - Nitrogen - Japanese - Norin 10 - Assimilate

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Borlaug's new semi-dwarf, disease-resistant varieties, called Pitic 62 and Penjamo 62, changed the potential yield of wheat dramatically. By 1963, 95% of Mexico's wheat crops used the semi-dwarf varieties developed by Borlaug. That year, the harvest was six times larger than in 1944, the year Borlaug arrived in Mexico. Mexico had become fully self-sufficient in wheat production, and a net exporter of the grain.{{mn|UoMGreenRev|14}} Four other high yield varieties were also released, in 1964: Lerma Rojo 64, Siete Cerros, Sonora 64, and Super X.

Related Topics:
1963 - 1944

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