Posts Tagged ‘stem rust’

Deadly strain of wheat stem rust disease surfaces in Europe

Scientists have shown that the first appearance of wheat stem rust disease in the U.K. in nearly 60 years, which occurred in 2013, was caused by the same virulent fungal strain responsible for recent wheat stem rust outbreaks in Ethiopia, Denmark, Germany, and Sweden.

Wheat stem rust was reported by the Greeks and Romans, and the latter sacrificed to the gods to avoid disease outbreaks on their wheat crops. Photo: CIMMYT/Petr Kosina

Wheat stem rust was reported by the Greeks and Romans, and the latter sacrificed
to the gods to avoid disease outbreaks on their wheat crops.
Photo: CIMMYT/Petr Kosina

As reported today in Communications Biology, an international team of researchers led by the John Innes Centre, U.K., found that 80 percent of U.K. wheat varieties are susceptible to the deadly stem rust strain. The group also confirmed for the first time in many decades that the stem rust fungus was growing on barberry bush, the pathogen’s alternate host, in the UK.

“This signals the rising threat of stem rust disease for wheat and barley production in Europe,” said Dave Hodson, senior scientist at the International Maize and Wheat Improvement Center (CIMMYT) and co-author on the study.

A scourge of wheat since biblical times, stem rust caused major losses to North American wheat crops in the early 20th century. Stem rust disease was controlled for decades through the use of resistant wheat varieties bred in the 1950s by scientist Norman Borlaug and his colleagues. Widespread adoption of those varieties sparked the Green Revolution of the 1960s and 70s.

In 1999 a new, highly-virulent strain of the stem rust fungus emerged in eastern Africa. Spores of that strain and variants have spread rapidly and are threatening or overcoming the genetic resistance of many currently sown wheat varieties. Scientists worldwide joined forces in the early 2000s to develop new, resistant varieties and to monitor and control outbreaks of stem rust and yellow rust, as part of collaborations such as the Borlaug Global Rust Initiative led by Cornell University.

Barberry is a shrub found throughout the temperate and subtropical regions. Photo: CIMMYT archives

Barberry is a shrub found throughout
the temperate and subtropical regions.
Photo: John Innes Centre

The Communications Biology study shows that 2013 U.K. stem rust strain is related to TKTTF, a fungal race first detected in Turkey that spread across the Middle East and recently into Europe. It was the dominant race in the 2013 stem rust outbreak in Germany and infected 10,000 hectares of wheat in Ethiopia’s breadbasket the same year.

Because disease organisms mutate quickly to overcome crop resistance controlled by single genes, researchers are rushing to identify new resistance genes and to incorporate multiple genes into high-yielding varieties, according to Ravi Singh, CIMMYT wheat scientist who participated in the reported study.

“The greatest hope for achieving durable resistance to rust diseases is to make wheat’s resistance genetically complex, combining several genes and resistance mechanisms,” Singh explained.

Barberry, which serves as a spawning ground for the stem rust fungus, was largely eradicated from the U.K. and U.S. last century, greatly reducing the spread and genetic diversification of rust disease races. Now barberry is being grown again in the U.K. over the last decade, according to Diane G.O. Saunders, John Innes Centre scientist and co-author of the study.

“The late Nobel laureate Norman Borlaug said that the greatest ally of the pathogen is our short memory,” Saunders stated. “We recommend continued, intensive resistance breeding. We would also welcome work with conservationists of endangered, barberry-dependent insect species to ensure that planting of common barberry occurs away from arable land, thus safeguarding European cereals from a large-scale re-emergence of wheat stem rust.”

Click here to read the John Innes Centre media release about the Communications Biology report and view the report.

Breakthrough in the battle against Ug99

Melania Figuroa and Peter Dodds
Thursday, January 25, 2018 (Posted on the Borlaug Global Rust Initiative web page)

Wheat stem rust at important flag leaf stage. Photo by Robert Park

A significant breakthrough in combatting wheat stem rust disease caused by the fungus Puccinia graminis f. sp. tritici was recently achieved through the combined work of an international collaborative team, showing the power of cooperative research approaches.

The emergence of the Ug99 race of stem rust in Africa and the Middle East together with the appearance of new strains in Europe catalyzed a major effort to identify new sources of stem rust resistance and breed these genes into wheat lines. However, the continued emergence of stem rust variants that overcome new resistance genes, now demands an increased focus on pathogen evolution and virulence mechanisms.

Numerous stem rust resistance (Sr) genes are known and in recent years several of these have been cloned and used to develop so-called ‘perfect’ markers to allow more rapid and accurate breeding. These genes typically encode immune receptors that recognize specific protein components of the fungal pathogen to trigger resistance. However, the molecules recognized by these Sr genes have been unknown until now, hampering our understanding of how new strains of P. graminis f. sp. tritici evolve to escape plant recognition.

New insight into this evolution came from the identification of the protein, AvrSr50, which is recognized by the wheat Sr50 resistance gene, by  an international collaboration led by Dr. Peter Dodds (CSIRO Food and Agriculture and University of Minnesota Adjunct Professor) and Professor Robert Park (University of Sydney and Director of theAustralian Cereal Rust Control Program) and involving teams in the UK and the US.

Click here to read the full article.

Kenya wheat breeders win the 2015 BGRI Gene Stewardship Award

By Julie Mollins/CIMMYT

NAIROBI, Kenya (October 8, 2015)- Plant pathologist Ruth Wanyera and wheat breeders Godwin Macharia and Peter Njau of the Kenya Agriculture and Livestock Research Organization (KALRO) received the 2015 Gene Stewardship Award at the Borlaug Global Rust Initiative Workshop (BGRI) in Sydney, Australia.

“The KALRO team has done an outstanding job – their work has had significant global impact by accelerating the capacity of developing countries to protect themselves against this swift-moving and devastating disease,” said Sridhar Bhavani, a wheat breeder who leads the International Maize and Wheat Improvement Center (CIMMYT) stem-rust screening nurseries in East Africa and nominated the team for the award.