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Department of Biology, College of Science, University of Kufa, Hilla, Iraq

ABSTRACT

 Two cotton lines, OK 2.3 and OK 1.2, which have low and high levels, respectively, or resistance to bacterial blight were derived from a cross between a highly susceptible line,  Ac 44, and an immune line, Im 216.  Final bacterial population densities of X anthomonas campestris pv. malvacearum in leaves of Ac 44, OK 2.3, OK 1.2 and 1M 216 were inversely related to host resistance.  Ultrastructural effects of the interactions between X. campestris pv. malvacearum and cotyledons and leaves of OK 2.3 and OK 1.2 were studied.  Fibrillar materials and enveloping films appeared around bacteria in both lines with 4 h after inoculation.  The average numbers of bacterial observed within each envelope increased with time in both lines.  After 48 h, most enveloping films had ruptured in the less resistant line, OK 2.3, and the bacteria had emerged from them.  Most envelopes were ruptured within 72 h in OK 1.2.  The results indicate that the enveloping structures do not prevent bacterial multiplication, but the persistence of envelopes is correlated with host resistance.