Whole Plant Wound Inoculation for Consistent Reproduction of Black Rot of Crucifers

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Abstract
Several widely used inoculation techniques were compared for their ability to reproduce black rot of crucifers caused by Xanthomonas campestris pv. campestris. The comparisons showed that different bacteria not normally pathogenic to crucifers can cause necrosis or maceration of turnip [Brassica campestris] and cauliflower [B. oleracea] leaves if the bacteria were infiltrated into detached leaves or inoculated into stems of 3-day-old seedlings. When inoculated similarly in leaves and 3-day-old seedlings, X. c. campestris also caused symptoms atypical of black rot that were visually indistinguishable from those caused by the other bacteria. In most instances black rot did not develop and was delayed in onset when it did. On the other hand, X. c. campestris was able to cause black rot quickly and at virtually all inoculation sites when inoculations were made at the hydathodes or wounds of intact plants. By this technique, Agrobacterium tumefaciens, Arthrobacter luteus, clavibacter michiganense subsp. michiganense, Erwinia carotovora subsp. carotovora, E. herbicola, E. stewartii, E. amylovora, Escherichia coli, Pseudomonas fluorescens, P. putida, P. viridiflava, Serratia marcescens, X. c. zinniae, X. c. begonia, X. c. malvacearum, X. c. oryzae, X. c. transluscens, X. c. vesicatoria, and X. c. vitians failed to cause black rot.