NORWICH, ENGLAND — Genetic analyses show that a destructive wheat blast fungus that travelled from South America to South East Asia is now established in Zambia under rain-fed conditions, according to a new report from The Sainsbury Laboratory.
Wheat blast, Magnaporthe oryzae, is a fungus with devastating implications for wheat crop. It was originally detected in Brazilian wheat fields in 1985 and quickly spread over most of the South American continent. In 2016, the first wheat blast pandemic beyond South America hit Bangladesh and officials had to destroy more than 15,000 hectares of crops to try and contain this virulent pathogen. Less than two years later, Zambian farmers were struck by the first wheat blast pandemic in Africa. Until now, there has been no confirmation if the same pathogen strain had spread to all three continents or if these pandemics were caused by endemic pathogens spreading from other grass species to wheat.
To answer this question, Prof. Sophien Kamoun and his team at The Sainsbury Laboratory in Norwich collaborated with Dr. Batiseba Tembo (Zambia Agriculture Research Institute), Prof. Tofazzal Islam (Institute of Biotechnology and Genetic Engineering in Bangladesh) and colleagues from The Graduate School of Agricultural Science in Japan, the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, the Laboratory of Evolutionary Biology in Switzerland and the Department of Entomology and Plant Pathology in Tennessee (US). Together, they analyzed samples of pandemic wheat blast from the three continents.
Molecular analyses showed that precisely the same set of 84 genetic markers were present in samples from Bangladesh, Zambia and Bolivia, linking the countries through a single pandemic clone. All the samples from Zambia collected from 2018 to 2020 were the same clone indicating that there was probably only one introduction. This was also the case for the Bangladeshi samples from 2016 to 2020, implying it’s unlikely that there were further introductions after the first one in 2016. The clone match found in Bolivia was sampled in 2012 and probably originated from other South American populations. This will later be confirmed using whole genome sequencing.
Open science and international collaborations were at the core of the successful tracing and identification of wheat blast clones from all over the world.
By creating the website Open Wheat Blast (go.nature.com/bkczwf), the rapid sharing of data was facilitated between researchers, which proved crucial for tracking wheat blast pathogens.
These findings rule out that the Zambian wheat blast pandemic was caused by a host jump from other African grass pathogens to wheat. The authors of the report, describing these new findings, conclude that the pathogen that caused the wheat blast pandemics in Bangladesh has spread to Zambia. There is also an indication that this same Zambian population has successfully established at different sites within the country.
Knowing that this pandemic clone is genetically similar to those in South America and Bangladesh means that Zambian farmers can benefit from using similar wheat blast management strategies that have proven successful over the years.
“At least we can now understand that it is not something that entirely originated from Zambia,” Tembo said. “Indeed, the knowledge gained from South America and Bangladesh can be confidently applied to Zambia to mitigate this worrisome disease.”
“The information generated is very important and has significant impact in developing and implementing wheat blast management strategies,” said Pawan Singh, head of wheat pathology at CIMMYT.