Detection: Xanthomonas axonopodis pv. allii.
Matrices: Pure cultures, seeds and infected tissues.
Other information: kit developed and optimized by Qualiplante according to Robène-Soustrade et al. (2010). Under CIRAD license.
The PCR primers used in this Duplex Nested End-Point PCR method are designed to target two sequences showing sequence similarity with bacterial genes encoding the PilW/PilX proteins (PIL marker) and the avrRxv virulence gene (AVR marker).
This method is referred in the Appendix 2 of the PM7/128 (1) Xanthomonas axonopodis pv. allii, European and Mediterranean Plant Protection Organization Bulletin (2016) 46 (3), 429-443.
Validation data of the method are available from a test performance study realized in 2014 by ANSES and CIRAD. The performance characteristics obtained are:
- Analytical sensitivity: 100% of samples were detected as positive at a concentration of 1×103 cfu mL-1. At 1×102 cfu mL-1, 81% samples tested positive.
- Analytical specificity: 100% inclusivity – 89% exclusivity (when considering the taxa). No amplification was obtained for any unrelated phytopathogenic bacteria or for any saprophytic bacteria commonly isolated from onion leaves and seeds. Cross-reactions with a few strains classified in axonopodis genetic subgroup 9.1 or 9.2: X. axonopodis pv. begoniae, X. axonopodis pv. vesicatoria, X. axonopodis pv. citrumelo, X. axonopodis pv. cassavae, X. axonopodis pv. desmodii, X. axonopodis pv. desmodiiganetici, X. axonopodis pv. phyllanthi, X. axonopodis pv. tamarindi and X. axonopodis pv. lespedezae, and also two strains of X. vasicola pv. musacearum. Depending on the pathovar, one or both markers were observed. The probability of finding these pathovars on onion plants or seeds is negligible because the capacity to induce symptoms on onion plants is specific to X. axonopodis pv. allii strains.
- Repeatability: from 1×104 to 1×103 cfu mL-1: 100%. At 1×102 cfu mL-1 accordance: 70%.
- Reproducibility: 100%.
The PCR kit of Qualiplante was tested in the same study and the same results were obtained in terms of specificity, sensitivity and reproducibility.
Included reagents: Direct Master Mix, Nested Master Mix, Negative Control,Positive Control.
Xanthomonas axonopodis pv. allii
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