Relationship of Polygalacturonase Enzyme Activity between Brown Rot Isolates and their Virulence on Potato Cultivars

Abstract

Ralstonia solanacearum, the bacterium that causes bacterial wilt in many plant species, produces a number of extracellular plant cell wall-degrading enzymes that are thought to be virulence factors. Endopolygalacturonase (endo-PG), PehA, and two exo-PGs, pehB and pehC, are among them. R. solanacearum was isolated and identified from sick potato tubers, yielding five isolates (BR1, BR2, BR3, BR4, and BR5). The pathogenicity of the isolates was determined, results revealed that the isolates differed in their virulence. R. solanacearum isolates (BR3, BR2, and BR5) had different levels of virulence on the potato stems of the examined cultivar (strong, moderate, and weak) respectively, so these isolates were chosen to assess potato cultivars for susceptibility to R. solanacearum isolates. R. solanacearum susceptibility differed amongst potato varieties. Spunta cultivar was the most sensitive, whereas Nicola cultivar was the most resistant. Mondial was a fairly sensitive cultivar. The activity of the PG enzyme was measured in the five isolates. BR3, BR2 and BR5 isolates were high, moderate and low activity, respectively. The optimum PG activity was observed at pH 5 and 5.5 and PG activity reached the highest level at 2 and 2.5 from incubation time, the maximum activity of PG was observed at 30 ºC and 40 ºC of incubation temperature, the optimum PG activity was observed with NaCl followed by CaCl2, The optimum NaCl concentrations for PG activity were 0.1 and 0.