Alliance Bioversity-CIAT Developing Nation Recipients
Head of Plant Pathology Unit, Plant Protection Center
(PPC), Department of Agriculture, Laos
Le Thi Hang, Researcher,
Research Institute of Vietnam (PPRI),
Technician, Plant Protection Center (PPC),
Department of Agriculture, Laos
First Report of Cassava Mosaic Disease and Sri Lankan Cassava Mosaic Virus in Laos
K. Chittarath1 ; J. Jimenez 2 ; P. Vongphachanh1 , A. M. Leiva2 ; S. Sengsay1 , D. Lopez- Alvarez2,3, T. Bounvilayvong1 , D. Lourido2 , V. Vorlachith1 , W.J. Cuellar2
1Minisitry of Agriculture and Forestry, Department of Agriculture, Plant Protection Center
2Virology Laboratory, Crops for Nutrition and Health, International Center for Tropical Agriculture
Cassava (Manihot esculenta Crantz) has been traditionally grown as a subsistence crop in Laos, but in recent years its cultivation has expanded and is becoming a ‘cash crop’. Cassava Mosaic Disease (CMD) is an important disease affecting cassava in the world. CMD is caused by several species of bipartite begomoviruses and is disseminated by infected stakes or vectored by the whitefly Bemisia tabaci. Sri Lankan cassava mosaic virus (SLCMV) is the virus species causing CMD in Southeast Asia (SEA) and several isolates from Cambodia, Vietnam, Thailand and south China have been characterized. During field surveys on July, 2020, along the border with Cambodia, in Attapeu and Champasack provinces we identified CMD symptoms in Kong District. From 8 fields, samples were collected from every third plant in an X pattern and photographs from each sampled plant were taken. Virus detection was done by PCR using specific primers targeting the AV1 and the BV1 gene. For one field in Kong district, 18.3% of the samples resulted PCR positive to SLCMV (DNA-A and DNA-B) but only 6.7% showed symptoms of CMD. We did not detect CMD symptoms nor SLCMV in any of the other seven fields surveyed. Sequence analysis show that all SLCMV isolates from SEA form a separate group and among them, a subgroup can be distinguishing which contain virus isolates that present a larger version of the rep gene. With this protocol, field surveillance continued, allowing us for the rapid detection and management of CMD in other provinces in Laos.
Keywords: Cassava Mosaic Disease; Southeast Asia; geminivirus; field surveillance.
Occurrence and distribution of Cassava Mosaic Disease (CMD) in Vietnam and its management
Le Thi Hang, Nguyen Van Liem, Trinh Xuan Hoat, Nguyen Manh Hung, Ngo Quang Huy, Le Quang Man, Mai Van Quan, Jonathan C. Newby, Wilmer J. Cuellar
Cassava (Manihot esculenta Crantz) is the third most important carbohydrate food crop in the tropics, after rice and maize. In Vietnam, cassava is also ranked third in terms of production area where the starchy root is proceeded into animal feed, bioethanol, and native and modified starch products that support a billion-dollar export industry. The productivity and economic competitiveness of Vietnam’s cassava sector is being threatened by the emergence and rapid spread of cassava diseases and insect pests, such as pink mealybug (Phenacoccus manihoti Matile-Ferrero), Cassava mosaic disease (CMD) and Cassava witches’ broom disease (CWBD) that are affecting cassava growing areas in Vietnam. CMD has emerged as one of the most serious threats to cassava production in Vietnam since 2016. Recent systematic field surveys throughout Vietnam showed the quick spread and serious damage of CMD from South to North. Some key molecular characteristics of Sri Lankan cassava mosaic virus (SLCMV), the causal agent of CMD in Vietnam, were analyzed which provided essential information for better understanding the spread of the disease and facilitate the prediction of CMD epidemics. Current experiments of pesticide treatments to cassava cuttings (planting material, Genus Begomovirus), showed good results for vector control. In addition, a protein-based diagnostic technology is currently carried out for rapid, handy, inexpensive, and accurate, and large-scale detection of SLCMV for effective management of CMD in Vietnam.
Evaluating LAMP-based field diagnostics for the management of cassava mosaic disease in Lao PDR
Pinkham Vongphachanh et al.
Cassava (Manihot esculenta, Crantz) is one of the most important staple food crops in Lao PDR after rice and Cassava mosaic disease (CMD) is a serious emerging threat to this crop. CMD can be caused by several species of begomoviruses but in Southeast Asia (SEA) Sri Lankan cassava mosaic virus (SLCMV) is the only virus species causing CMD in (SEA) reported so far.. Early detection of pathogen requires rapid detection protocols to confirm the disease symptoms observed, here we evaluated a new device which is portable and produce results in 1 hours. All leaf samples were first analyzed by PCR using primers specific for SLCMV and then by using the CMD field detection droid. The samples were taken from plants in field of Vientiane capital showing suspicious symptoms of CMD and include samples showing no symptoms The samples were macerated leaf tissue in extraction buffer and then extracted using dipsticks., The nucleic acids were then eluted directly into LAMP reaction mix and incubated into the Droid (8 samples for each time). The result returned in 60 min for accurate of identification all these samples with symptoms gave positive with the droid. The results confirm for the first time the occurrence of CMD and SLCMV in Vientiane, and the droid proved useful in the field. Currently we are evaluating its application in determining the quarantine state of the planting material before import within the country.
Keyword: Cassava (Manihot esculenta, Crantz), begomoviruses , Cassava mosaic disease, Sri Lankan cassava mosaic virus (SLCMV), Diagnostic droid