Taking the Scientists to the Rust

Cally Arthur
Thursday, October 27, 2016

Saha Bir Rai doesn't see stem rust in his fields in Bhutan. “We have wheat varieties but we don’t understand levels or types of rust,” said the senior plant protection officer in the Division of Pest Surveillance at Bhutan’s National Plant Protection Center.

In early October, the Kenya Agriculture and Livestock Research Organization (KALRO) changed all that for young wheat scientists like Bir Rai who have not experienced stem rust in the field.

Armed with the information he has gained from breeders and pathologists in the 8th annual course, “Standardization of stem rust note taking and evaluation of germplasm with emphasis on emerging threats of yellow rust and leaf rust,” Bir Rai can expand his wheat phenotyping activities in Bhutan.

Senior plant protection officer Saha Bir RaiBir Rai and the other 22 participants now have the knowledge to conduct a rust survey and score national varieties against a common set of parameters. They have learned that disease assessment classifies plants into groups/lines: lines exhibiting early susceptibility that are “rust suckers,” lines with resistance protected by major genes, and lines that are “slow rusting” or protected by minor genes.

The course took place 2-12 October 2016 at KALRO’s Njoro Station, in Nakuru, Kenya, coordinated by Sridhar Bhavani, CIMMYT wheat scientist and international phenotyping coordinator at KALRO, Njoro. This year’s 10-day program was paid for by the Delivering Genetic Gain in Wheat (DGGW) project. As in years’ past, it combined classroom discussions and field exercises on standardization and evaluation of germplasm against stem rust to train pathologists and breeders in the area of rust research.

Classroom topics ranged from population genetics and molecular markers to pathogen nomenclature, rust types and surveillance techniques. Other lectures focused on the life cycle of stem rust fungus, pathogen-host interaction, and how to conduct greenhouse and field phenotyping evaluations.

Trainers included international wheat rust experts such as Robert McIntosh, Dave Hodson, Ruth Wanyera, Godwin Macharia, Maricelis Acevedo, and others.

After several days of classroom learning, trainees went to the field with instructions from Ravi Singh, CIMMYT plant breeder: “Select the plant you want to become a variety in your country.” Trainees faced thousands of rows of F4 and F5 populations. The selected plants will undergo further trials and selection at the CIMMYT stations in Obregon and Toluca, Mexico, before being tested in international and national trials.

Another oft-repeated message during training was the “747” or “airplane” effect. Participants learned that the white biohazard suits they wore in the field in Njoro are not complete protection from transferring the pathogen back home. The fungus moves on people — not just on shoes that are disinfected at the airport — but on soiled trousers in suitcases. When a scientist or visitor walks in a farm infected with cereal rust, he picks up the spores on his trousers and can become the unwitting vector for the disease to travel around the world and back to his or her home wheat fields.

Neighboring Ethiopians in attendance

Five participants in the workshop were from nearby Ethiopia. They are very familiar with stem rust and already score wheat in their home research centers but came to Njoro to sharpen their knowledge about the fungus and evaluate Ethiopian wheat lines that are in field trials at the KALRO Station. They are evaluating lines for traits that include grain quality and vigor, but especially how the lines respond to rust pressure.  

Zerihun Tadesse, national wheat breeding coordinator at the Ethiopian Institute for Agricultural Research (EIAR), in Kulumsa, was in the field during much of the program. He was selecting and scoring 490 observation nurseries from three locations in Ethiopia that originated from CIMMYT lines, more than 220 advanced lines from preliminary variety and national trials, and 15 recently released varieties.

“It’s those lines with good disease resistance and best overall performance in Ethiopian environments that will continue in the breeding pipeline headed for farmers’ fields,” he said. Tadesse noted that although he came to Njoro for selection and scoring, he really liked attending lectures to stay current on the research.

The international community of wheat rust researchers at Njoro is just that: scientists committed to sharing their knowledge. A critical message throughout the workshop was the importance of scientists from national programs participating in pathogen surveys and sharing their data globally. 

Robert McIntosh, the internationally renowned wheat pathologist who is a fount of knowledge on the subject, told the trainees, “Durable is a set of genes that passes the test of time — not time spent in the germbank — the test of time in farmers’ fields.”

The tireless and effective educator also said, “To understand the pathogen you can take the scientist to the rust, or the rust to the scientist.”

At the CIMMYT training at Njoro, the scientists came to the rust.