COLONIZATION OF ROOTS OF STRAWBERRY CULTIVARS WITH DIFFERENT LEVELS OF SUSCEPTIBILITY TO PHYTOPHTHORA-FRAGARIAE

Roots of strawberry cultivars Tennessee Beauty (susceptible), Surecrop (partially resistant), and Climax (highly resistant) were examined microscopically at 2, 4, 6, 8, and 10 days after inoculation with Phytophthora fragariae race Pf-2. Cultivar Climax had no infection hyphae or reproductive organs of P. fragariae at any time period or distance from the root tip. Cultivar Surecrop roots were colonized at a slower rate and had fewer reproductive organs than had Tennessee Beauty. The lack of sporangial production (secondary inoculum) on Surecrop substantiates previous findings of few or no sporangia produced on Surecrop roots 14 days after inoculation with P. fragariae race Pf-2. Restriction or reduction in sporangial production may be a component of partial resistance to P. fragariae.