METHOD: Chemical Assay CONDITIONS: Field METHOD NARR: Tubers that had been stored for 3 months were surface sterilized. Pipet tips containing a suspension of the bacteria were pressed to a depth of 10mm and left in place. Aftern, the tubers were sliced vertically through the infection points and the width of decayed tissue measured. Seperate innoculated tubers were sliced vertically to the injection points and tissue surrounding the injection sit to determine the activities of PPO and PO. RESULTS NARR: Parental, fusion hybrid and cultivar material was used. Hexaploid somatic hybrids of brd and tbr cv Russet Burbank showed PPO activity 2 times higher than Russet Burb of the hybrids was also higher in the periderm and medullary tissue. Results also show resistance to bacterial soft rot in the hybrid tubers. Wounding and infection induced an increase in PPO and PO activities in all samples tested,s higher and better stabilized in the hybrids. AUTHOR EXPLANATION: The results showed that the high activity of phenol oxidating enzymes may be one of the factors that affect the periderm resistance to bacterial soft roe overall resistance mechanism. Anaerobic conditions exclude the functioning of PPO and PO.