Development of excised shoot and root assays for in vitro evaluation of Banksia species for response to Phytophthora species.

Abstract

Excised shoot and root assays were evaluated for routine screening for Phytophthora resistance or tolerance in a Banksia breeding programme. An excised root assay provided useful information on the response of 15 Banksia species to Phytophthora cinnamomi and P. citricola. Roots were excised from 9- to 12-month-old plants, inoculated with plugs of mycelium, and sampled to establish the extent of colonization. Species susceptibility, expressed as the extent of root colonization at day 8, gave good agreement with previously published results obtained for plants inoculated in a shadehouse containment facility. This assay also showed differences in susceptibility among individual plants of B. baxteri and B. coccinea. An excised shoot assay was considered unsuitable for routine screening because lesion development in 16 species was found to be inconsistent when performed over 3 years. Preliminary evaluation of an assay using micropropagated shoots is reported.