PEROXIDASE ISOENZYMES IN STRAWBERRY ROOTS INFECTED WITH BINUCLEATE RHIZOCTONIA SPP. AND THEIR IMPLICATION IN DISEASE RESISTANCE

Infection of strawberry plants with binucleate Rhizoctonia spp. result s in an increase in peroxidase activity and the appearance of new isof orms of the enzyme. In healthy and diseased roots of two different str awberry genotypes seven peroxidase isoenzymes were found. In healthy s trawberry cv. Senga Sengana, which was moderately resistant to infecti on, 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 resista nce to binucleate Rhizoctonia may be correlated with peroxidase isoenz yme profile with particular reference to isoform 3, which is only pres ent in infected roots of the moderately resistant cv., Senga Sengana.