Cassava mosaic disease and its management in Southeast Asia.

KEY MESSAGE: Status of the current outbreak of cassava mosaic disease (CMD) in Southeast Asia was reviewed. Healthy cassava seed production and dissemination systems have been established in Vietnam and Cambodia, along with integrated disease and pest management systems, to combat the outbreak. Cassava (Manihot esculenta Crantz) is one of the most important edible crops in tropical and subtropical regions. Recently, invasive insect pests and diseases have resulted in serious losses to cassava in Southeast Asia. In this review we discuss the current outbreak of cassava mosaic disease (CMD) caused by the Sri Lankan cassava mosaic virus (SLCMV) in Southeast Asia, and summarize similarities between SLCMV and other cassava mosaic begomoviruses. A SATREPS (Science and Technology Research Partnership for Sustainable Development) project "Development and dissemination of sustainable production systems based on invasive pest management of cassava in Vietnam, Cambodia and Thailand", was launched in 2016, which has been funded by The Japan International Cooperation Agency (JICA) and The Japan Science and Technology Agency (JST), Japan. The objectives of SATREPS were to establish healthy seed production and dissemination systems for cassava in south Vietnam and Cambodia, and to develop management systems for plant diseases and insect pests of cassava. To achieve these goals, model systems of healthy seed production in Vietnam and Cambodia have been developed incorporating CMD-resistant planting materials through international networks with The International Center for Tropical Agriculture (CIAT) and The International Institute of Tropical Agriculture (IITA).

Field transcriptome analysis reveals a molecular mechanism for cassava-flowering in a mountainous environment in Southeast Asia.

KEY MESSAGE: The field survey in this article showed in 'KU50', a popular variety and late-branching type of cassava in Southeast Asia, that flowering rarely occurs in normal-field conditions in Southeast Asia but is strongly induced in the dry season in the mountainous region. Flowering time is correlated with the expression patterns of MeFT1 and homologs of Arabidopsis GI, PHYA, and NF-Ys. Cassava (Manihot esculenta Crantz) is a tropical crop that is propagated vegetatively rather than sexually by seed. Flowering rarely occurs in the erect-type variety grown in Southeast Asia, but it is known that cassava produces flowers every year in mountainous regions. Data pertaining to the effect of environmental factors on flowering time and gene expression in cassava, however, is limited. The aim of the present study was to determine the kinds of environmental conditions that regulate flowering time in cassava and the underlying molecular mechanisms. The flowering status of KU50, a popular variety in Southeast Asia and late-branching type of cassava, was monitored in six fields in Vietnam and Cambodia. At non-flowering and flowering field locations in North Vietnam, the two FLOWERING LOCUS T (FT)-like genes, MeFT1 and MeFT2, were characterized by qPCR, and the pattern of expression of flowering-related genes and genes responsive to environmental signals were analyzed by using RNA sequencing data from time-series samples. Results indicate that cassava flowering was induced in the dry season in the mountain region, and that flowering time was correlated with the expression of MeFT1, and homologs of Arabidopsis GI, PHYA, and NF-Ys. Based upon these data, we hypothesize that floral induction in cassava is triggered by some conditions present in the mountain regions during the dry season.

Occurrence of antibiotic residues and antibiotic-resistant bacteria in effluents of pharmaceutical manufacturers and other sources around Hanoi, Vietnam.

Pharmaceutical manufacturers in Vietnam are producing a wide variety of antibiotics for human and veterinary use. Consequently, the water discharged from those facilities can contain residues of antibiotics, which could have adverse impact on the environment. However, studies on the occurrence of antibiotics in the wastewater from pharmaceutical manufacturers in Vietnam are almost non-existent. In this study, water samples were collected at around the outlets of four pharmaceutical manufacturing plants as well as from a hospital and an aquaculture farm around Hanoi in 2016 and 2017. Fifteen antibiotics from four major classes (ß-lactam, quinolones, macrolides, sulfonamides) were monitored, using a validated LC-MS/MS method, based on their number of registrations at the Ministry of Health. Ten antibiotics, ampicillin, cefuroxime, cefotaxime, clarithromycin, azithromycin, sulfamethoxazole, trimethoprim, ofloxacin, norfloxacin, and ciprofloxacin were detected in the samples at different concentrations. Notably, sulfonamides and quinolones were occasionally detected at very high concentration, such as sulfamethoxazole (252 µg/L), trimethoprim (107 µg/L), ofloxacin (85 µg/L), and ciprofloxacin (41 µg/L). In this study, concentrations of antibiotic residues in effluent of pharmaceutical plants were higher than those from other sources. The antibiotic-resistance tests indicated the widespread resistance to common antibiotics like quinolone and sulfonamides in the collected samples. This finding suggests that wastewater from pharmaceutical manufacturers could be an important source of antibiotics and antibiotic-resistant bacteria in the aquatic environment of Vietnam.