Detection of Ralstonia solanacearum race 4 in field samples using a combination of serological and molecular assays. M. L. PARET (1), R. Kubota (1), D. M. Jenkins (1), A. M. Alvarez (1)
(1) University of Hawaii at Manoa
Phytopathology 98:S120

Abstract: Ralstonia solanacearum race 4 (Rs) causes bacterial wilt of edible ginger (Zingiber officinale). Serological and DNA-based assays were evaluated for detecting low populations of Rs in soil and effluent water. Rs strain A4515 was poured over soils containing wounded and non-wounded gingers. Survival of Rs in effluent water and/or soil samples was analysed for 150–180 days after inoculation (DAI) by viable plate counts, ELISA, PCR and LAMP. Soil and effluent water samples also were analyzed by an Immunostrip assay and results were compared with viable plate counts. Recovery of viable Rs was 2 log units higher from soil samples than from effluent water collected from the same pot. ELISA using Ps1, an anti-EPS mAb, showed consistent positive results for effluent water with Rs populations above log 4.0 cfu/mL. An immunostrip assay based on Ps1a, a similar antibody, gave positive results for effluent water when culturing showed Rs populations of log 1 cfu/mL. Likewise, immunostrip results were positive in soil samples containing log 2 cfu/g. Both PCR and LAMP detected Rs in effluent water with populations above log 3 cfu/mL. Rs-EPS was detectable in effluent water till 130 DAI (log 1 cfu/mL) by immunostrips while ELISA, PCR and LAMP assays in effluent water samples detected Rs for only 50 DAI. The immunostrip assay is highly sensitive and can be effectively used in combination with other assays for assessing Rs in field samples.