Effect of soil-matric potential and phylloplanes of rotation-crops on the survival of a bioluminescent Xanthomonas campestris pv. campestris

The survival of the bacterial pathogen, Xanthomonas campestris pv. campestris (Xcc), was studied in plant debris-infested soil with different matric potentials (0, -10, -30, -50, -100, -200, and -900 kPa), and on the phylloplane of crops used for rotation with cabbage. Populations of cellulolytic and proteolytic microorganisms were studied in relation to soil matric potential and Xcc. The survival of Xcc was negatively correlated (r = -0.710; P = 0.06) with soil matric potential and with the abundance of cellulolytic microorganisms (P = 0.05). In saturated soil, Xcc survived for only 19-28 days, while at -900 kPa there was no significant change in the bacterial population within this period. Survival of Xcc on the phylloplane of cabbage (Brassica oleracea var. capitata) (host) was similar to that on mustard and lettuce (48 days), whereas the pathogen was detected for only 9 days on rice. It appears that high matric potentials reduced populations of Xcc in soil, whereas epiphytic survival of this pathogen depended on the plant species.