Peroxidase isoenzymes in strawberry roots infected with binucleate Rhizoctonia spp. and their implication in disease resistance

Infection of strawberry plants with binucleate Rhizoctonia spp. results in an increase in peroxidase activity and the appearance of new isoforms of the enzyme. In healthy and diseased roots of two different strawberry genotypes seven peroxidase isoenzymes were found. In healthy strawberry cv. Senga Sengana, which was moderately resistant to infection, four isoenzymes (1, 2, 5, and 6) were found. Moreover the activity of these isoenzymes was increased and three new isoenzymes (3, 4, and 7) were found in infected roots. In the strawberry hybrid 3/2/86/88/R, which is very susceptible to infection, only isoenzyme 2 was present in the roots of healthy plants. Following infection, the activity of isoenzyme 2 was increased and five new isoenzymes (1, 4, 5, 6, and 7) were detectable. The results obtained indicate that strawberry resistance to binucleate Rhizoctonia may be correlated with peroxidase isoenzyme profile with particular reference to isoform 3, which is only present in infected roots of the moderately resistant cv., Senga Sengana.