Development of a Sensitive and Specific Polyclonal Antibody for Serological Detection of Clavibacter michiganensis subsp. sepedonicus

Antibacterial Activity of Dihydroquercetin Separated from Fructus Polygoni orientalis against Clavibacter michiganensis subsp. sepedonicus via Damaging Cell Membrane

The yield and quality of potato can be severely affected by bacterial ring rot, which is caused by Clavibacter michiganensis subsp. sepedonicus (Cms). Recently, using natural compounds to control bacteria has received more attention. In this study, five antibacterial compounds from ethyl acetate (EtOAc) extract of Fructus Polygoni orientalis (FPO) against Cms were isolated and the most active compound was screened. Five active compounds were identified as 3,3'-di-O-methylellagic acid (1), 3,3'-di-O-methylellagic acid-4-O-β-D-glucopyranoside (2), dihydroquercetin (3), protocatechuic acid (4) and quercetin (5). Compound 3 (dihydroquercetin, DHQ) was confirmed as the most active compound. The diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), protective efficiency and curative efficiency of DHQ were 22.50 mm, 0.313 mg/mL, 84.49% and 79.63%, respectively, which exceeded these of thiophanate-methyl (TM) in antibacterial activity assays; this indicated that DHQ had satisfactory antibacterial activities against Cms in vitro and in vivo. Results of cell membrane damage assessments indicated that DHQ could reduce membrane potential (MP), disrupt the cell membrane integrity, and promote the leakage of nucleic acids and proteins. Overall, these findings suggested that DHQ could serve as a promising lead molecular against Cms, which could provide a basis for its further derivatization.

Detection of Potato ring rot Pathogen Clavibacter michiganensis subsp. sepedonicus by Loop-mediated isothermal amplification (LAMP) assay

Clavibacter michiganensis subsp. sepedonicus (CMS) is an important bacterial plant pathogen causing potato ring rot disease. Rapid diagnosis of CMS is crucial because of the economic losses caused by serious harvest losses. Although there are serological tests used in the rapid diagnosis of CMS, they are not widely used because of their low sensitivity. The DNA-based PCR methods, which are highly sensitive, do not have the possibility of on-site diagnosis, especially since they require serious laboratory infrastructure. In recent years, scientists have been working on alternative amplification methods to develop DNA-based point of care (POC) diagnostic methods. Accordingly, the loop-mediated isothermal amplification (LAMP) method, which was developed in the early 2000s, provides an important convenience for DNA-based tests to use in the field. Due to the unique design of primers, more amplification products could be create in a shorter time than conventional amplification methods without needing a temperature cycle, and it can be applied with the aid of a simple heater without requiring a laboratory environment. In this study, efficient LAMP method for the detection of CMS has optimized. For device-independent detection of LAMP products, colorimetric method and LFD has used.

Synergetic effect of non-complementary 5' AT-rich sequences on the development of a multiplex TaqMan real-time PCR for specific and robust detection of Clavibacter michiganensis and C. michiganensis subsp. nebraskensis

Clavibacter is an agriculturally important genus comprising a single species, Clavibacter michiganensis, and multiple subspecies, including, C. michiganensis subsp. nebraskensis which causes Goss's wilt/blight of corn, accounts for high yield losses and is listed among the five most significant diseases of corn in the United States of America. Our research objective was to develop a robust and rapid multiplex TaqMan real-time PCR (qPCR) to detect C. michiganensis in general and C. michiganensis subsp. nebraskensis with enhanced reliability and accuracy by adding non-complementary AT sequences to the 5’ end of the forward and reverse primers. Comparative genomic analyses were performed to identify unique and conserved gene regions for primer and probe design. The unique genomic regions, ABC transporter ATP-binding protein CDS/ABC-transporter permease and MFS transporter were determined for specific detection of C. michiganensis and C. m. subsp. nebraskensis, respectively. The AT-rich sequences at the 5’ position of the primers enhanced the reaction efficiency and sensitivity of rapid qPCR cycling; the reliability, accuracy and high efficiency of the developed assay was confirmed after testing with 59 strains from inclusivity and exclusivity panels–no false positives or false negatives were detected. The assays were also validated through naturally and artificially infected corn plant samples; all samples were detected for C. michiganensis and C. m. subsp. nebraskensis with 100% accuracy. The assay with 5’ AT-rich sequences detected up to 10- and 100-fg of C. michiganensis and C. michiganensis subsp. nebraskensis genome targets, respectively. No adverse effect was observed when sensitivity assays were spiked with host genomic DNA. Addition of 5’ AT-rich sequences enhanced the qPCR reaction efficiency from 0.82 (M = -3.83) and 0.91 (M = -3.54) to 1.04 (with optimum slope value; M = -3.23) for both C. michiganensis and C. michiganensis subsp. nebraskensis, respectively; an increase of 10-fold sensitivity was also obtained with C. michiganensis primer set. The methodology proposed here can be used to optimize reaction efficiency and to harmonize diagnostic protocols which have prodigious applications in routine diagnostics, biosecurity and microbial forensics.