Orenstein, J., Gilat Regional Experiment Station, Agricultural Research Organization, Mobile Post Negev 2, 85280, Israel, Center for Plant Breeding Research (CPO), Wageningen, 6700 AA, Netherlands
Nachmias, A., Gilat Regional Experiment Station, Agricultural Research Organization, Mobile Post Negev 2, 85280, Israel, Center for Plant Breeding Research (CPO), Wageningen, 6700 AA, Netherlands

The feasibility of selecting potato tolerance, in the pollen stage, to Verticillium wilt was evaluated using a phytotoxic Verticillium dahliae protein-lipo-polysaccharide complex which was isolated from culture filtrates of a fungal isolate pathogenic to potato. The toxin, at concentrations of 10 mg/ml and above, significantly reduced both germination and tube growth in vitro of pollen from the disease-susceptible potato genotypes, Promesse and Solanum phureja IvP35, but not from the tolerant genotypes, Alpha and WA–85–4–5. Vital staining showed that inhibition of germination was not due to pollen death. Although toxin-sensitivity of pollen mirrored that of excised potato leaves or cultured roots, cell suspensions, and plantlets, reduction in germination occurred only at toxin concentrations 100-fold higher than that required to cause damage to vegetative potato tissue. The results suggested that this bioassay may be useful for selection in pollen before pollination. © 1994 Taylor & Francis Group, LLC.