Innovative techniques in wheat breeding are necessary to meet the increasing population demand and overcome environmental challenges, said Ravi Singh at the 2012 American Association for the Advancement of Science (AAAS) meeting, Feb. 16-20, in Vancouver.
Singh, Cornell plant breeding and genetics adjunct professor and distinguished wheat breeder at the International Center for Maize and Wheat Improvement (CIMMYT), in Mexico, said that enhanced breeding techniques such as shuttle breeding are helping create new durably disease resistant varieties of wheat that will increase yields to better meet global demand.
Speaking as a panelist in the "Emerging Risks in the Global Food System," a session organized by William E. Fry, Cornell professor of plant pathology, Singh noted that wheat yields need to increase one ton/hectare by 2020 to keep pace with the growing population. Rising global temperatures and new, virulent diseases will decimate yields even further. These pressures are especially felt in developing countries where wheat provides 20% of the daily protein intake for the average person, said Singh.
Wheat diseases, like Ug99, exert particular pressures on wheat in developing countries. Ug99, a stem rust first discovered in Uganda in 1998, attacks and destroys entire fields of wheat, overcoming the genetic resistance that protects a vast majority of the world's wheat. The fungus spreads via wind currents and accidental human transmission. It has broken out of eastern Africa and is poised at the edge of the breadbaskets of Pakistan and India.
Norman Borlaug, Nobel Prize laureate and father of the Green Revolution, recognized the threat and convened a meeting of the world's leading wheat researchers in 2005. Out of that meeting, the Durable Rust Resistance in Wheat (DRRW) project, administered by Cornell's College of Agriculture and Life Science and funded by the Bill and Melinda Gates Foundation and the UK Department of International Development, was created to organize and mobilize research to create new wheat varieties that are both resistant to Ug99 and provide increased yields. Singh collaborates with scientists in national programs around the world to breed new varieties of wheat that meet the threat.
Singh extends a method initiated by Borlaug, shuttle breeding, to identify and breed promising varieties of wheat more quickly. The process starts by planting seed in CIMMYT test fields in the irrigated Yaqui Valley, in Obregon, Mexico, and selected materials are then brought to test fields in Toluca, over 1000 miles to the southeast, outside Mexico City at high altitude and high rainfall There the plants are subjected to different soil types, temperatures, environmental and disease pressures. Because the growing seasons occur at different times of year Singh can subject his samples to two growing seasons in one calendar year, cutting the breeding time in half.
The selected plants in breeding populations are then grown at screening nurseries in Njoro, Kenya, administered by the Kenya Agricultural Research Institute, for two generations under high Ug99 pressure and then brought back to Mexico. Selection in last breeding generations and testing for grain yield performance, tolerance to heat and drought stresses, bread quality, resistance to various diseases are then conducted in Mexico. . The end result is varieties well-suited to varied environments that offer good yield and strong disease resistance. More than 20 Ug99-resistant varieties have been released or are in advanced trials in eight countries, including India and Pakistan.
"We have made great strides in identifying new varieties that will provide durable resistance to stem rusts and increase yields," said Singh, "but there is still much work to be done because of the importance of wheat and the ever-changing pressures it faces globally."