An agglutination test for fast and specific detection of Erwinia psidii

• Published in: Forest pathology = Journal de pathologie forestière = Zeitschrift für Forstpathologie Vol. 49; no. 5
• Main Authors: Montoya‐Estrada, Claudia N., Silva, Patrick F., Costa, Camila R., Oliveira, Leandro L., Guimarães, Lúcio M.S., Badel, Jorge L., Alfenas, Acelino C., Desprez‐Loustau, Marie‐Laure
• Format: Journal Article
• Language: English
• Published: Berlin Wiley Subscription Services, Inc 01-10-2019
• Subjects: Agglutination; Amplification; Antibodies; Antigens; Bacteria; Biochemical tests; Deoxyribonucleic acid; Dieback; DNA; Endophytes; Enzyme-linked immunosorbent assay; Erwinia; Eucalyptus; Pathogens; Phylogeny; Plant tissues; Polyclonal antibodies; polyclonal antibody; Polymerase chain reaction; Primers; Psidium guajava; Strains (organisms); Wilt
• ISSN: 1437-4781; 1439-0329
• DOI: 10.1111/efp.12549

Dieback and wilt, caused by Erwinia psidii (Ep), is one of the most important emergent diseases of Eucalyptus spp. in Brazil. Currently, pathogen detection relies on isolation of bacteria from infected plant tissue and either identification based on morphological, physiological and biochemical tests or DNA amplification using the polymerase chain reaction (PCR), which in many cases is laborious and cumbersome. Considering the need for a simpler and more rapid, yet reliable, method for detecting the pathogen, we obtained a polyclonal antibody (anti‐Ep) and developed an agglutination test for specific detection of E. psidii. The antiserum was produced against the E. psidii strain LPF534 and tested against 101 E. psidii isolates from Eucalyptus spp.; three E. psidii isolates from Psidium guajava; 23 Ralstonia solanacearum and 18 Xanthomonas axonopodis isolates pathogenic to Eucalyptus spp.; and seven endophytic isolates from Eucalyptus spp., three of which are phylogenetically related to the genus Erwinia. Results of direct ELISA indicated that a concentration as low as 3.5 µg/ml of the anti‐Ep antibody was able to detect the E. psidii antigen and that the antibody did not cross‐reacted with other bacteria pathogenic and non‐pathogenic to Eucalyptus spp. In the agglutination test, the anti‐Ep antibody showed positive reaction with all strains of E. psidii tested whereas cross‐reaction with none of the strains that belong to other taxonomic groups was observed. The agglutination test showed a detection limit of 105 colony‐forming units (CFU)/ml, and its specificity was the same as that obtained by PCR amplification using E. psidii‐specific primers. These results demonstrate that the agglutination test developed here is a useful tool for specific, fast and inexpensive detection of E. psidii although only operational on pure bacterial suspensions and not yet directly from infected tissues.