Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/1997
Publication Date: N/A
Technical Abstract: Polymerase chain reaction (PCR) primers, XAF1/XAR1 were selective in detecting XA, the causal agent of leaf scald of sugarcane. The primers produced a ca. 600 bp band for all 19 XA strains tested but not for any of the 9 other pathovars of X. campestris (12 strains) pathogenic to other hosts, and 5 unidentified yellow saprophytes isolated from sugarcane. Detection of XA in suspensions of pure cells and vascular bundle sap and leaf leachates of sugarcane was compared using classical PCR, dot immunobinding assay (DIA), ELISA, and isolation techniques. A 10 min boiling treatment of leaf and stalk extracts eliminated inhibitors that interfered with PCR assays. Also, classical PCR was compared with BIO-PCR (biological amplification before PCR). As few as 360 to 800 colony forming units (CFU) of XA per ml of spiked vascular bundle sap or pure cell suspensions were detected by PCR. DIA and ELISA required 83,000 and 14,000 CFU per ml sample. All techniques detected XA 100% of the symptomatic stalks. XA was detected in latently infected stalks (asymptomatic) by isolation and by both PCR techniques. Since BIO-PCR has the advantage of confirming the putative identity of viable colonies of XA on culture medium, this combined agar medium-PCR technique is recommended.