From Norin 10 to the Green Revolution
Norin 10 began to attract international attention after a visit by Salmon SD, a renowned wheat breeder in the U.S. Department of Agriculture (USDA), to Morioka Agriculture Research Station in Honshu (Borojevic and Borojevic 2005). Salmon took some samples of the Norin 10 variety back to the United States, which were sent on to a joint Washington State University (WSU) /USDA project at Pullman, Washington (Reitz and Salmon 1968). At WSU in 1949, Dr. Vogel began to use these semi-dwarf varieties extensively and a series of crosses were made, including Norin 10 × Baart and Norin 10 × Brevor.
As previously mentioned, Vogel supplied the Norin 10 × Baart and Norin 10 × Brevor crosses to Dr. Borlaug and the Mexico wheat breeding program. In 1952 and 1953, the Mexican wheat program focused its efforts on tackling the problem of lodging (Borlaug 1981). With varieties such as Chapingo 52, Lerma Rojo 53 and Yaqui 50, the heavy application of nitrogen fertilizer led to severe lodging and yield loss.
After unsuccessfully screening the entire USDA World Wheat Germplasm collection to find shorter and strong varieties, Borlaug wrote to Vogel and requested seed containing the Norin 10 dwarfing genes.
Borlaug detailed in 1981 that the first attempt at incorporating the Vogel genes into the Mexican varieties failed. He attributes this lack of success to the fact that the F3 plants produced from Dr. Vogel's seed were used as female parents and as a result were highly susceptible to rust.
The second attempt was successful and a new type of wheat with higher yield was evident in the F1 and F2 progeny from those crosses. So much so, that from 1957 nearly all of the Mexican wheat breeding efforts focused on the Norin 10 × Brevor derivatives.
Not only was dwarfness of stature introduced into the crosses from the Norin 10 derivities, but also a number of other genes had been introduced, which increased the number of fertile florets per spikelet, the number of spikelets per head and the number of tillers per plant. (Norman Borlaug 1981)
At first, Borlaug encountered a number of problems with progeny from the cross Norin 10 × Brevor × Mexican varieties:
1. High degree of male sterility leading to promiscuous outcrossing
2. Poor grain that was shriveled, soft and with low gluten content
3. Susceptibility to stem and leaf rust.
The new and innovative shuttle breeding program, introduced by Borlaug, between El Batán, located at an altitude of 2,249 m in the Central Mexican highlands, and Ciudad Obregón located in the irrigated desert in the Northern Sonora Valley, meant that two generations per year could be grown to speed up selection against the above mentioned problems. The exposure of the breeding materials to contrasting locations and diverse environmental constraints also allowed Borlaug and his team to select for a broader range of disease resistances (Ortiz-Garcia et al. 2006).
By 1962, 10 years after Vogel first supplied seed of the Norin 10 Japanese semidwarf progeny to Borlaug, two high-yielding semi-dwarf Norin 10 derivatives, Pitic 62 and Penjamo 62, were released for commercial production (Reynolds and Borlaug 2006). As Fig. 2.2 indicates, these wheat varieties then led to a flow of other high-yielding wheat varieties, including Siete Cerros 66, which at its peak was grown on over 7 million hectares in the developing world (Reynolds and Borlaug 2006).