Wheat's amazing short story
GroundCover™ Issue: 126 | Author: Dr Gio Braidotti
Having recently been a participant in the consortium that launched an international initiative to raise wheat yield potential by up to 50 per cent, the International Maize and Wheat Improvement Center (CIMMYT) looks back at the dwarfing genes that changed wheat growing forever
About 98 per cent of Australia’s wheatbelt is sown to varieties derived from the genebank and breeding programs of the International Maize and Wheat Improvement Center (CIMMYT). It has been estimated that CIMMYT germplasm directly adds an estimated $30 million a year to Australian farms. This germplasm is characterised by the Australian crop’s semi-dwarf stature.
On its 50th anniversary in 2016, CIMMYT commemorated the productivity revolution that was leveraged from the use of dwarfing genes, and also looked to the future and the genetic traits needed to drive the next step-change in yields.
CIMMYT has produced a history that traces the origin of short wheat varieties to Korea in about the third or fourth century. From East Asia, villagers began selecting for this short stature (plants that were expressing the dwarfing gene) to breed varieties with higher yield potential, resistance to lodging and the ability to produce more tillers than traditional varieties.
In 1935, Japanese scientist Gonjoro Inazuka crossed a semi-dwarf Japanese wheat landrace with two American varieties, resulting in a further improved variety known as Norin 10.
The term Norin is an acronym for the Japanese Agricultural Experiment Station spelled out using Latin letters. Norin 10 contains dwarfing genes Rht-B1b and Rht-D1b that reduced wheat height from 150 centimetres to 60 and 110cm.
Norin 10 began to attract international attention following a visit by S.D. Salmon, a wheat breeder from the US Department of Agriculture (USDA), to Marioka Agriculture Research Station on Honshu.
Salmon took some Norin 10 samples back to the US where in the late 1940s, Orville Vogel at Washington State University used them to help produce high-yielding, semi-dwarf, winter wheat varieties. The first was called Gaines.
Lines derived from Norin 10 eventually ended up in the hands of Dr Norman Borlaug in Mexico. This international exchange of germplasm is now credited by CIMMYT with saving hundreds of millions of people from starvation through its contribution to the Green Revolution.
Dr Borlaug and his team were focusing their efforts on tackling the problem of lodging and rust resistance. After unsuccessfully screening the entire USDA World Wheat Germplasm Collection for shorter and stronger varieties, Borlaug wrote to Vogel and requested seed containing the Norin 10 dwarfing genes. He struck it lucky: Norin 10 provided both short stature and rust resistance.
In 1953, Borlaug began crossing Vogel’s semi-dwarf, winter wheat varieties with Mexican varieties. The first attempt at incorporating the Vogel genes into Mexican varieties failed. But after a series of crosses and re-crosses, the result was a new type of spring wheat – short, stiff-strawed varieties that tillered profusely, produced more grain per head and were less likely to lodge.
The semi-dwarf Mexican wheat progeny was distributed nationally and within seven years average wheat yields in Mexico had doubled. By 1962, 10 years after Vogel first supplied Norin 10 progeny to Dr Borlaug, two high-yielding, semi-dwarf varieties, Pitic 62 and Penjamo 62, were released for commercial production. These wheat varieties led to a flow of other high-yielding wheat varieties.
At this time, South Asia was facing mass starvation and extreme food insecurity. To meet this challenge, scientists and governments in the region began assessing the value of Mexican semi-dwarf wheat varieties. Trials in India and Pakistan were convincing, producing high yields, but only after agronomy practices were changed. Importantly, the semi-dwarf varieties were resistant to local rust strains.
Grasping the potential, M.S. Swaminathan, a wheat cytogeneticist and adviser to the Indian Minister of Agriculture, invited Dr Borlaug to visit India. Borlaug immediately accepted.
The two wheat varieties that led to the Green Revolution in India, Pakistan and other countries are Sonora 64 and Lerma Rojo 64. Subsequently, the Mexican spring wheat Siete Cerros 66 was grown on more than seven million hectares at its peak. However, the most widely grown variety during this period was the very early-maturing variety Sonalika, which is still grown in India today.
The Green Revolution produced wheat yield improvements in India and Pakistan unlike anything seen before. Fifty years on, CIMMYT faces new challenges and is committed to achieving another quantum leap in wheat productivity. The International Wheat Yield Partnership (IWYP) is exploiting the best wheat research worldwide to increase wheat yield potential by up to 50 per cent.
The first round of funding through IWYP was announced in 2015, with five of the eight approved research projects drawing on Australian research capability and three projects headed by Australian researchers: Barry Pogson (Australian National University), Richard Trethowan (University of Sydney) and Stuart Roy (University of Adelaide).
The IWYP envisages a wheat plant with increased biomass and an optimised plant and root architecture that captures more sunlight and uses it more efficiently to produce more and larger grain. This amounts to a new kind of wheat plant with transformative levels of yield and productivity for adaptation to local environments.
The GRDC is contributing more than $10 million over three years to fund the Australian streams of the IWYP projects.
- International Maize and Wheat Improvement Center
- International Wheat Yield Partnership
- Australian researchers named in global plan to double wheat yield – GRDC video
Region Overseas, South