Journal of Plant Pathology & Microbiology

Abstract

Comparison of DAC-ELISA and Tissue Blot Immunoassay for the Detection of Acidovorax avenae subsp. avenae, causal agent of Red Strip of Sugarcane

Syed Zia-Ul-Hussnain, Rauf CA, Haque MI, Shahid Afghan, Tariq Mukhtar, Farah Naz, Kausar Nawaz Shah M and Aamir Shahazad

Direct Antibody Coating Enzyme Linked Immunoassay (DAC-ELISA) and Tissue Blot Immunoassay (TBIA) were compared for detection of Acidovorax avenae subsp. avenae (Aaa) in sugarcane samples surveyed in 2010 and 2011. A total of 27 sugarcane clones contained two samples of symptomatic plants, which were tested simultaneously by both serological tests. The results obtained from DAC-ELISA tests showed that 11 of 27 tested samples of sugarcane clones were infected with Aaa and 16 were bacteria free; whereas, in duplicate samples only 7 samples were positive for Aaa using the TBIA. The TBIA membranes showed dark blue stain colour in the 7 positive and 20 were negative. It was concluded that the DAC-ELISA had false positives in the 4 clones (SPF-238, CP77-400, SPF-213 and GT-11) that were negative using TBIA. Assay time was also minimized in performing TBIA test as equivalence to DAC-ELISA. Related to the test performing time at least 25-30 hours were consumed for the completion of DAC-ELISA assay, while only 6-9 hours was required for TBIA assay with reliable results. Both assays gave Aaa positive for clones HoSG-315, CPSG-437, NSG-49, CPSG-2453, CP-NIA-82-223, CSSG-2402 and US-114. TBIA tests were distinct with clear positive and negative results having minimum diagnostic error. On the other hand quantitative assay of bacteria is a significant feature of DAC-ELISA but low optical density readings above background were inconsistent with the TBIA and were considered false positive results. Amongst the variety of immunological tests available in Pakistan, tissue blot immunoassay (TBIA) is most useful in detecting latent infections in the plant materials.