Tracking The Spread Of Cassava Mosaic Virus

The Sri Lankan cassava mosaic virus threatens 3.5 million hectares of crops in Southeast Asia, highlighting the need for disease-resistant varieties, say researchers.

AsianScientist (Mar. 11, 2019) – An international team of researchers has documented the spread of the Sri Lankan cassava mosaic virus (SLCMV) over a single growing season to inform disease control measures. Their findings are published in PLOS ONE.

In 2015, news that the potentially harvest-devastating Sri Lankan cassava mosaic virus (SLCMV) was spreading in Cambodia raised alarm. Since then, containment measures have not improved due to difficulties in detecting the virus, demonstrating the virus’ potential to become a major threat to the livelihoods of millions of smallholder farming families who grow the cash crop on more than 3.5 million hectares in Southeast Asia, generating over US$4 billion of export revenue.

In the present study, researchers led by Assistant Professor Nami Minato at the International Center for Tropical Agriculture, Colombia, recorded how SLCMV spread over a single growing season to obtain a systematic baseline evaluation of SLCMV in Southeast Asia.

The researchers collected some 6,500 samples from 420 fields in Vietnam and Cambodia during the 2016 sampling period, and discovered 49 SLCMV-infected plants across two provinces in Eastern Cambodia. While this represented only a two percent infection rate, since that time the disease was reported in Vietnam and Thailand, suggesting that SLCMV has taken hold in Southeast Asia.

The team used molecular techniques to detect positive infections, paired with photographs of each individually sampled plant to look for visual disease symptoms. 14 percent of infected plants did not display typical visual symptoms, said the researchers.

Quarantine measures, restrictions on the movement of cut stems—which are sold across the region to plant new fields in a loosely regulated informal market—and eradication measures might still offer a means to control the disease. But because SLCMV is also spread by a species of whitefly (Bemisia tabaci), methods to eliminate or reduce the population of whitefly may also be necessary.

Long-term development of resistant varieties of cassava will likely be needed to control SLCMV, necessitating considerable investment in breeding programs over many years, the researchers added.

“Documenting the outbreak and spread at an early stage is critical for understanding the dynamics of the epidemic, and pre-empting or responding effectively to future ones,” said Mr. Erik Delaquis, a co-author of the study at the International Center for Tropical Agriculture based in Vientiane, Laos.

The article can be found at: Minato et al. (2019) Surveillance for Sri Lankan Cassava Mosaic Virus (SLCMV) in Cambodia and Vietnam One Year After Its Initial Detection in a Single Plantation in 2015.


Source: International Center for Tropical Agriculture.
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