Pectobacterium carotovorum (Pc) causing potato tuber soft rot uses N-acyl-L-homoserine lactones (AHLs) to control the production of virulence factors via quorum sensing (QS). Some bacteria produce enzymes to inactivate the AHL signals of pathogenic bacteria via a phenomenon known as quorum quenching. One hundred bacterial isolates from potato tubers were screened for AHL-degrading activity using biosensor strain Chromobacterium violaceum CV026. Of these isolates, 20 were able to inactivate AHLs from the pathogenic bacteria in vitro. Of the 20 isolates, 6 attenuated tissue maceration of potato tubers by Pc. Suppression of tuber soft rot was observed even when these isolates were applied 24 h after the pathogen was introduced. Their colonization in tubers was approximately 10 3 -10 4 cfu/g tuber, 7 days after inoculation. These isolates were identified as Bacillus sp., Variovorax sp., Variovorax paradoxus and Agrobacterium tumefaciens. Four of these isolates showed putative AHL-lactonase activity and provided the most significant protection against Pc. Therefore, AHL-degrading endophytic bacteria can be utilized as a novel biocontrol agent of potato tuber soft rot in Vietnam.
Southern rice black-streaked dwarf virus (SRBSDV) causes severe epidemical disease on rice with the infected area up to millions of hectares in South China and North and Central of Vietnam. So far, there are no effective, cheap, quick, and practicable methods for diagnosing SRBSDV. The conventional RT-PCR technique is the most popular method for detecting SRBSDV with high accuracy. However, it is hard to apply this method for large-scale SDBSDV diagnosis because of the requirements of expensive reagents and instruments, as well as complex procedures. Meanwhile, SRBSDV diagnostic techniques based on antigen detection have outstanding advantages due to their low cost, easy manipulation, and wide application possibility. Today, there are still no commercially available specific antibodies to SRBSDV. In a previous study, to develop the SRBSDV diagnostic technique by the ELISA technique, a SRBSDV specific antibody was generated by a recombinant P10 envelope protein (66kDa), which has a titer of 1:5,000. In this study, we continued to study the production of SRBSDV specific polyclonal antibodies from small antigen–rich peptides from the SRBSDV P10 envelope protein. The resulting purified antibody can specifically bind to the P10 protein and at the diluted concentration of 1:100,000 it can detect SRBSDV in infected rice samples via the dot-blot technique. Our research results open up new opportunities for proactive antibodies to develop a SRBSDV membrane rapid diagnostic kit.
Coffee is an important crop in Vietnam and it has recently brought a lot of benefit for the country through export. After coffee leaf rust, anthracnose is the second destructive disease for coffee production and is caused primarily by Colletotrichum gloeosporioides. In order to investigate the pathogenicity of C. gloeosporioides on coffee in the North of Vietnam, we carried out isolation of C. gloeosporioides species from different coffee plantations and found that C. gloeosporioides presents in different parts of coffee including leaf, twig, ripe berry and green berry. The pathogenicity of a total of twenty eight C. gloeosporioides isolates was tested on green berry in laboratory. Interestingly, two most pathogenic isolates were originated from green berry. In detail, the rate of green berry infection by C. gloeosporioides isolates varied from 4.44% to 76.67% and the variation of infection rate was also observed clearly among C. gloeosporioides isolates originating from leaf (14.40% to 45.56%), twig (4.44% to 58.89%), ripe berry (22.20% to 61.10%) and green berry (24.40% to 76.67%). Three selected pathogenic isolates representing for C. gloeosporioides isolates originated from twig, ripe berry and green berry were further tested for pathogenicity on hypocotyl seedling in greenhouse. The rate of hypocotyl seedling infection by C. gloeosporioides isolates originated from twig, green berry and ripe berry is 48.89%, 37.78 and 23.33% respectively. Our data suggests that pathogenicity of C. gloeosporioides is variable and specific among isolates, parts of coffee.
Bac thom 7 rice (BT7 rice) is one of the major elite rice cultivars in Vietnam with superior productivity and quality but very susceptible to bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae. The gene OsSWEET14, belonging to the OsSWEET family which encodes sugar transport proteins, is considered to be a susceptible gene involved in the virulence of Xoo. At least three cis-elements (EBE - Effector-binding element), including Tal5, PthXo3 and AvrXa7 on BT7 OsSWEET14 promoter, bind specifically to well-known transcription activator–like effectors (TALEs) of many Asian Xoo bacterium strains. In this study, a T-DNA construct which expressed the protein-RNA complex CRISPR/Cas for editing three EBEs position on the OsSWEET14 promoter was designed. The recombinant binary vector was tested by PCR, restriction enzyme and finally sequencing and then successfully transferred to Bac thom 7 rice through Agrobacterium tumefaciens. 28 of 30 hygromycin-resistant regenerated rice lines that grew and developed normally under nethouse conditions were selected by PCR with specific primers. Among these, twelve transgenic rice lines were identified carrying one copy of the T-DNA construct. The presence of CRISPR/Cas9-induced mutations of the targeted promoter in the transgenic plants were confirmed by T7EI assay. These results provide the basis to determine the role of OsSWEET14 in the susceptibility of Bac thom 7 rice to Xanthomonas oryzae pv. oryzae -caused disease, towards the further goal of generating an improved Bac thom 7 rice variety with broad-spectrum bacterial leaf blight resistance using CRISPR/Cas9 technology.
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