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Magnaporthe oryzae is the causal agent of rice blast disease resulting in yield losses in rice-growing regions worldwide, particularly in Vietnam. Up-regulation of osa-miR7695 was observed in blast resistant rice cultivars in comparison with blast non-resistant rice cultivars. The OsNramp6 gene is a target for osa-miR7695, and considered a factor involved in rice immunity but scant evidence has demonstrated systematic expression profiles of OsNramp6 transcript variants involving M. oryzae susceptibility and resistance of rice plants. In this study, a real-time qPCR (qRT-PCR) approach was used to evaluate the expression levels of eight OsNramp6 transcript variants in various Vietnamese rice cultivars. Results indicated that OsNramp6.1 and OsNramp6.4 transcript variants showed decreased expression levels at 24 hpi in M. oryzae resistant rice cultivars and vice versa in the rice group of M. oryzae resistance, suggesting that both could be used as potential markers for discrimination between blast resistant and non-resistant Vietnamese rice cultivars. Identification of potential microRNAs in rice that contribute to the regulation of OsNramp6 transcripts-mediated facilitation of infection by M. oryzae has still to be confirmed for elucidating their roles in rice immunity against M. oryzae.

We investigated the influence of convenient diets on big-eyed bug Geocoris ochropterus. Development and reproduction of G. ochropterus fed on convenient diets of ant pupae Oecophylla smaragdina and silkworm pupae Bombyx mori were examined using aphids Aphis gossypii as the control diet. Results showed that Geocoris ochropterus nymphs completed development to adults on all diets. Total average development period was 35.1 days fed on ant pupae, 35.9 days fed on silkworm pupae, and 36.0 days fed on aphids. Head width, body length, forewing length, and fresh body weight of adults were not affected by diets, except for females reared on ant pupae that were significantly heavier than those fed on aphids. There was no significant difference in offspring sex ratio. Total number of eggs deposited per female fed on ant pupae was significantly larger than when fed on aphids, while eggs laid by females fed on silkworm pupae were significantly longer than eggs laid by females fed on aphids. Results suggest that ant pupae and silkworm pupae could be effectively used for mass rearing of G. ochropterus.

Magnaporthe oryzae causes rice blast disease, which leads to devastating yield losses in Vietnam and other rice-growing countries. Recent studies indicated that 30% of rice- growing areas are affected by rice blast disease. MicroRNAs (miRNAs) are short non-coding RNAs that are related to plant development and biotic stress tolerance. Osa-miR7695 as one of the common miRNAs, and its target the OsNramp6 gene were evaluated as factors that contribute to the pathogenic activity of different rice cultivars. The expression profile of microRNA osa-miR7695 was evaluated to identify blast resistance or susceptibility in rice cultivars. Results of RT-PCR and real-time qPCR indicated the presence of osa-miR7695 in most Oryzae sativa Indica group cultivars in Vietnam. Upregulation of osa-miR7695 observed in blast resistant rice cultivars at different infection time intervals was higher than in blast non-resistant rice cultivars. Expression of the OsNramp6 gene increased in blast non-resistant cultivars, particularly at 72 h post inoculation. Average ΔCt values of osa-miR7695 in blast resistant rice cultivars were higher by approximately 4-fold than in blast non-resistant rice cultivars. Results suggested osa-miR7695 as a potential biomarker for microRNA based detection of blast resistance and non-resistance in Vietnamese rice cultivars to improve understanding of the biological role of microRNA in rice immunity.

PCR-based molecular approaches including RAPD (random amplified polymorphic DNA), ISSR (inter-simple sequence repeat), and SRAP (sequence-related amplified polymorphism) are commonly used to analyze genetic diversity. The aims of this study are to analyze genetic diversity of M. oryzae isolates using PCR-based molecular approaches such as RAPD, ISSR, and SRAP and to develop SCAR marker linked to the pathogenicity of rice blast fungus. Twenty Magnaporthe oryzae isolates were collected mainly from the south of Vietnam and assessed for genetic variation by RAPD, ISSR, and SRAP methods. The comparison of those methods was conducted based on the number of polymorphic bands, percentage of polymorphism, PIC values, and phylogenetic analysis. Then, sequenced characterized amplified region (SCAR) markers were developed based on specific bands linked to fungal pathogenicity of rice blast fungus, M. oryzae. The results indicated that SRAP markers yielded the greatest number of polymorphic bands (174) and occupied 51.7% with polymorphism information content (PIC) value of 0.66. Additionally, the SRAP approach showed stability and high productivity compared with RAPD and ISSR. The SCAR marker developed from the SRAP method identified the presence of the avirulence AVR-pita1 gene involving fungal pathogenicity that can break down blast resistance in rice cultivars. The consistency of SCAR marker obtained in this study showed its efficiency in rapid in-field detection of fungal pathogenicity. SCAR marker developed from SRAP technique provides a useful tool for improving the efficiency of blast disease management in rice fields.

Sugarcane white leaf disease (SWLD) and grassy shoot disease (SGSD) are caused by phytoplasma transmission between plants through insect vectors and infected cane setts, resulting in severe reduction of global yield and quality. Vietnam has large areas of sugarcane cultivation, and huge losses are caused by SWLD and SGSD, which impact on the sugar industry and local farmers. The current situation is summarized, and strategies to control white leaf and grassy shoot phytoplasma-associated sugarcane diseases in Vietnam are presented.

Parasitoids are important biological control of crop pests. In Vietnam, Cotesia vestalis is a native wasp species that has demonstrated its applicability as a natural insect pest enemy. Many adult parasitoids require food resources such as nectar and pollen to optimize their life cycles. Potential effects of yellow cosmos (Cosmos sulphureus), shrub verbena flower (Lantana camara), common zinnia (Zinnia elegans), and coriander flower (Coriandrum sativum L.) on the longevity and parasitism of C. vestalis were investigated. Results showed that nutrition resources from yellow cosmos (C. sulphureus) and shrub verbena flower (Lantana camara) significantly increased the longevity of C. vestalis in comparison with water (P < 0.001). Kaplan-Meier estimates of survival functions of female Cotesia vestalis exposed to different food sources indicated a significant difference in the treatments (P < 0.01). Male and female wasps feeding on Cosmos sulphureus, Lantana camara, and Coriandrum sativum survived significantly longer than wasps fed on water or Zinnia elegans. Parasitism efficiency of C. vestalis was tested on diamondback moth Plutella xylostella (L.) larvae for different food resources. Cosmos sulphureus, Lantana camara, Coriandrum sativum treatments gave the different mean number of emergence parasitoids per day compared to water treatment. Results implied that food resources from flowers benefitted the longevity of C. vestalis.

Parasitoids are important biological control of crop pests. In Vietnam, Cotesia vestalis is a native wasp species that has demonstrated its applicability as a natural insect pest enemy. Many adult parasitoids require food resources such as nectar and pollen to optimize their life cycles. Potential effects of yellow cosmos (Cosmos sulphureus), shrub verbena flower (Lantana camara), common zinnia (Zinnia elegans), and coriander flower (Coriandrum sativum L.) on the longevity and parasitism of C. vestalis were investigated. Results showed that nutrition resources from yellow cosmos (C. sulphureus) and shrub verbena flower (Lantana camara) significantly increased the longevity of C. vestalis in comparison with water (P < 0.001). Kaplan-Meier estimates of survival functions of female Cotesia vestalis exposed to different food sources indicated a significant difference in the treatments (P < 0.01). Male and female wasps feeding on Cosmos sulphureus, Lantana camara, and Coriandrum sativum survived significantly longer than wasps fed on water or Zinnia elegans. Parasitism efficiency of C. vestalis was tested on diamondback moth Plutella xylostella (L.) larvae for different food resources. Cosmos sulphureus, Lantana camara, Coriandrum sativum treatments gave the different mean number of emergence parasitoids per day compared to water treatment. Results implied that food resources from flowers benefitted the longevity of C. vestalis.

Quantitative RT–PCR and overexpression studies of two Dicer-like proteins, MoDcl1 and MoDcl2, in Magnaporthe oryzae indicated that the functional diversification of the MoDcl1 and MoDcl2 proteins in RNA-mediated gene silencing pathways was likely to have arisen from both transcriptional control and protein specialization.