Screening Trifoliate Hybrid Citrus Rootstocks for Resistance to Phytophthora parasitica by in Vitro Inoculation

in HortScience
Author: Kim D. Bowman1
View More View Less
  • 1 USDA, ARS, USHRL, 2120 Camden Rd., Orlando, FL 32803

Phytophthora parasitica Dast. causes several root and trunk diseases of citrus, including damping-off, root rot, foot rot, and gummosis. Phytophthora resistance is needed in Citrus rootstocks and is available in Poncirus trifoliata (L.) Raf. and some hybrids between Citrus and P. trifoliata. Field or greenhouse tests of rootstocks require large amounts of space and time. To provide a preliminary indication of rootstock resistance to P. parasitica, nucellar seedlings of P. trifoliata selections, and Citrus × P. trifoliata hybrids were tested for response to P. parasitica by in vitro inoculation. Seeds of individual selections were germinated in sterile culture and 3-week-old shoots were excised and inoculated with a cultured isolate of Phytophthora. After 1 week of incubation, response to the disease organism was measured by length of stem discoloration. Progression of Phytophthora in the stem also was measured by plating sequential 5-mm segments of the shoot and determining presence or absence of Phytophthora in individual segments. Stem discoloration length corresponded with location of Phytophthora in the stem. Relative resistance, as measured by this technique, approximated field resistance for several common rootstock cultivars. Resistant, intermediate, and susceptible selections were found in populations of Citrus × P. trifoliata rootstock hybrids using in vitro inoculation.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 51 15 3
PDF Downloads 96 50 4