Development of a PCR test for detection of Xanthomonas campestris pv. raphani

Leaf spot of Brassica is an important bacterial seed borne disease caused by X. campestris pv. raphani (Xcr), one of the three pathovars of Xanthomonas campestris species which makes significant economic loss throughout the world. A rapid and reliable detection method will be helpful for early diagnosis of the disease. To do that, we designed Xcr specific sequence-characterized amplified region (SCAR) markers from the Xcr specific genomic fragments, identified by aligning the whole genome sequences of several closely related bacterial pathovars and other bacterial species. Our primer set Xcr_59 produced Xcr specific amplicon of 679 bp in PCR assays. This primer pair was also capable of detecting Xcr strains directly from the artificially infected leaf samples prepared by suspending the diseased leaf area in sterile water without extracting bacterial DNA. This rapid, sensitive and reliable detection technique will be useful for adopting any firsthand plant protection measures against the disease.