Abstract:
Leaf responses of a susceptible potato cultivar (S. tuberosum cv. Valor) were compared to those of a tolerant potato cultivar (S. tuberosum cv. BP1) following challenge by Pectobacterium carotovorum subsp. brasiliense 1692 (Pcb 1692). Leaves of the susceptible cultivar showed excessive maceration and water soaking symptoms as well as increased proliferation of the bacteria. In leaves of the tolerant cultivar, bacteria appeared to be restricted to the point of inoculation,subsequently; there was very little multiplication of bacterial cells. Furthermore we demonstrated that disease is associated with the extensive spread of cell death in S. tuberosum cv. Valor while in S. tuberosum cv. BP1 cell death was observed to be associated with lack of disease development. Another response associated with challenge by Pcb 1692 in the susceptible and tolerant potato cultivar leaf tissue was the oxidative burst. Generally, the accumulation of hydrogen peroxide and superoxide in leaf-tissue appeared to correlate with tolerance levels.
