Cassava, Manihot esculenta Crantz, is the third-largest source of food carbohydrates, after rice and maize, in the tropics. On the Indian subcontinent, production of cassava can be severely affected by the cassava mosaic disease (CMD) caused by two Begomovirus species (Geminiviridae), Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV). In Southeast Asia, however, CMD was not known until May 2015, when the first CMD outbreak was observed in Cambodia, and the causal agent was identified as SLCMV (Wang et al. 2016). Here, we report the first outbreak of CMD in Vietnam. In May 2017, cassava plants showing typical CMD symptoms, including chlorotic mosaic, leaf distortion, and stunted growth, were observed in the field in Tay Ninh, Vietnam. Two symptomatic and two non-symptomatic cassava leaves as well as two whiteflies on symptomatic leaves were collected from each of four independent farmer's fields. Three whiteflies were also collected from an adjacent field with no symptomatic pl...

The fall armyworm, Spodoptera frugiperda, is an important agricultural pest native to tropical and subtropical regions of the Western Hemisphere, and has invaded Africa and further spread into most countries of Asia within two years. Here, we analyzed the genetic variation of invaded populations by comparing the nucleotide sequences of two genes: the nuclear Z-chromosome linked gene triose phosphate isomerase (Tpi) and the mitochondrial gene cytochrome oxidase subunit I (COI) of 27 specimens collected in Africa (DR Congo, Tanzania, Uganda, and Zimbabwe) and Asia (Bangladesh, Korea, Nepal, and Vietnam). The results revealed that 25 specimens were from a heterogeneous hybrid (Tpi-corn strain and COI-rice strain; Tpi-C/COI-R) of the corn strain male and rice strain female, but two specimens were from a homogenous corn strain (Tpi-corn strain and COI-corn strain; Tpi-C/COI-C). The further analysis of the fourth exon and the fourth intron sequences of the Tpi gene identified at least four subgroups of the corn strain. These four genetic subgroups were identified in Africa and Asia, suggesting no significant genetic change due to the rapid migration within two years. Our study provides essential information for understanding the genetic diversity of fall armyworm in new habitats.

Summary: Here we report that rRNA and mRNA are specifically degraded in oat (Avena sativa L.) cells during apoptotic cell death induced by victorin, a host‐selective toxin produced by Cochliobolus victoriae. Northern analysis indicated that rRNA species from the cytosol, mitochondria and chloroplasts were all degraded via specific degradation intermediates during victorin‐induced apoptotic cell death but, in contrast, they were randomly digested in necrotic cell death induced by 30 mm CuSO₄ and heat shock. This indicates that specific rRNA cleavage could be controlled by an intrinsic program. We also observed specific cleavage of mRNA of housekeeping genes such as actin and ubiquitin during victorin‐induced cell death. Interestingly, no victorin‐induced mRNA degradation was detected with stress‐responding genes such as PR‐1, PR‐10 and GPx throughout the experimental period. The RNA degradation mostly, but not always, occurred in parallel with DNA laddering, but pharmacological studies indicated that these processes are regulated by different signaling pathways with some overlapping upstream signals.

The nested-PCR technique was applied to detect and identify phytoplasmas associated with major crops in Vietnam including sugarcane, cassava and longan. Phylogenetic analysis confirmed that phytoplasmas associated with the sugarcane grassy shoot and white leaf diseases belong to the rice yellow dwarf group (16SrXI). In cassava showing witches’ broom symptoms a mixed infection of phytoplasmas related to ‘Candidatus Phytoplasma asteris’ (group 16SrI) and ‘Ca. P. aurantifolia’ (group 16SrII) was detected. In samples showing longan witches’ broom disease three phytoplasmas including ‘Ca. P. aurantifolia’ (group 16SrII), elm yellows (group 16SrV) and “stolbur” (group 16SrXII) were identified.

Background: Fusarium root rot disease in Indian mulberry (Morinda officinalisHow.) (FRRBK), caused byFusarium proliferatum(FP), is widespread and responsible for serious economic losses in Viet Nam. The efficacy of a new bio-product named MICROTECH-1(NL) is compared with other commercial products for suppression of FP under in vitro, pot, nursery as well as in the field conditions.Results: In in vitro antagonistic assay, MICROTECH-1(NL) significantly inhibited the mycelial growth of FP (72.38%). Under pot conditions, the efficacy of all the bio-products was significantly higher when applied prior to pathogen inoculation. The disease severity of treatments with double application of MICROTECH-1(NL) (applied both in the nursery and in the pot soil) was only 15.56%, significantly lower than control (80%). Thus, the application of MICROTECH-1(NL) significantly reduced the incidence of FP and markedly increased the number of plant beneficial bacteria and actinobacteria in rhizoplane ofM. officinaliscompared to untreated control. In the field conditions, double application of MICROTECH-1(NL) (both in the nursery and in the field soils) significantly decreased disease severity in comparison to single application in nursery or field.Conclusion: The most effective treatment was double application of MICROTECH-1(NL), which significantly reduced the disease severity and FP population in roots ofM. officinalisand increased the population of plant beneficial microbes.

Root rot is the most serious disease affecting Indian mulberry in Viet Nam. The objective of the present study was to confirm the identities and pathogenicity of species of Fusarium isolated from the roots of Indian mulberry. Based on pathogenicity assays, F. proliferatum was shown to be the pathogenic agent. The identity of F. proliferatum was confirmed by PCR and phylogenetic analyses based on the sequences of the ITS region and the TEF1-α gene. Of four semi-solid media (CA, PDA, CDA and YMA) tested, PDA was the most suitable medium for the growth of F. proliferatum. The optimal temperature range for the growth of F. proliferatum was 20–30 °C with a maximum at growth rate at 25 °C. The optimum pH for growth ranged from pH5.0–6.0 with maximum growth at 5.5. This is the first report of F. proliferatum causing root rot of Indian mulberry in Viet Nam.