Use of Monoclonal Antibodies to Monitor the Dissemination ofXanthomonas campestrispv.campestris

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Abstract
Monoclonal antibodies (MCA) were used to detect and differentiate strains of Xanthomonas campestris pv. campestris isolated from cabbage black rot lesions collected from the field. Extracts from leaf lesions were spotted onto a semiselective medium (FS). Four-day-old cultures that appeared to contain Xanthomonas were tested without further purification with four MCA using indirect enzyme-linked immunosorbent assay. The MCA reactivity patterns of four strains of X. c. pv. campestris were stable through four sets of serial transfers onto culture media and serial passages through cabbage. The four strains were introduced to replicate field plots on inoculated transplants, and dissemination of each strain was tracked independently with the MCA. Xanthomonas-like colonies were recovered on FS from 98% of samples (341 of 348) of lesions with definite black rot symptoms; 88% of the 341 presumptive Xanthomonas cultures on FS were identified as one of the four test strains by serotyping cultures directly from the isolation medium. The method also was useful in testing 484 lesions with symptoms that did not resemble those of black rot; the inoculated strains of X. c. pv. campestris were recovered from 21%. Pathogenic and nonpathogenic xanthomonads with MCA patterns unike those of the four introduced strains of X. cv. pv. campestris also were found in the field trials by this method. By monitoring the spread of the four inoculated strains of X. c. pv. campestris with MCA, disease progression and spatial patterns of infections were determined for each strain.