Abstract:
Brown rot or bacterial wilt of potato caused by Ralstonia solanacearum, is an economically important
disease. Potato, cv. Nicola, was found to be relatively highly resistant to the infection with
R. solanacearum and showed 15.12% wilt disease index, meantime, cv. Kara showed intermediate
resistance with 37.40% disease index while, cv. Spunta was susceptible and showed 80.33% disease
index. The role of defense-related enzymes in imparting resistance in potato against R. solanacearum
was investigated by quantifying enzymes activity and gene expression of three defenserelated
enzymes, peroxidase, polyphenol oxidase and catalase. Peroxidase showed maximum activity
0.488 min−1∙g−1 early at 12 h after pathogen inoculation in the cv. Nicola, whereas in susceptible
cultivar Spunta showed lower activity of maximum 0.226 min−1∙g−1 later at 48 h after inoculation.
While, the moderately resistant cultivar Kara showed intermediate activity for the peak
and its time. Meanwhile, polyphenol oxidase showed similar trends to that of peroxidase. On the
contrary, catalase showed the highest activity values in the susceptible, cv. Spunta, while, in relatively
highly resistant (cv. Nicola) and the moderately resistant (cv. Kara) showed lower values of
activity and up to 96 h after inoculation. Meanwhile, gene expression of related enzymes the
RT-PCR was used. At zero time, the relatively highly resistant potato cultivar, Nicola, showed the
highest values of gene expression for both Peroxidase (POD) and Poly Phenol Oxidase (PPO).
While, the susceptible potato cultivar, Spunta showed the lowest values. On the contrary, Catalase
(CAT) gene expression was the highest in the susceptible, cv. Spunta, and was the lowest in the
relatively highly resistant, cv. Nicola, while, was of intermediate values in the intermediate resistance,
cv. Kara. Results show that peroxidase and polyphenol oxidase activities can be used as biochemical
markers to reveal the resistance and susceptibility nature of potato cultivars against
bacterial wilt disease of potato caused by R. solanacaerum.
