THE EFFECT OF A VERTICILLIUM-DAHLIAE PHYTOTOXIN ON GERMINATION OF POTATO POLLEN

The feasibility of selecting potato tolerance, in the pollen stage, to Verticilliun wilt was evaluated using a phytotoxic Verticillium dahli ae protein-lipopolysaccharide complex which was isolated from culture filtrates of a fungal isolate pathogenic to potato. The toxin, at conc entrations of 10 mg/ml and above, significantly reduced both germinati on and tube growth in vitro of pollen from the disease-susceptible pot ato genotypes, Promesse and Solanum phureja IvP35, but not from the to lerant genotypes, Alpha and WA-85-4-5. Vital staining showed that inhi bition of germination was not due to pollen death. Although toxin-sens itivity of pollen mirrored that of excised potato leaves or cultured r oots, cell suspensions, and plantlets, reduction in gemination occurre d only at toxin concentrations 100-fold higher than that required to c ause damage to vegetative potato tissue. The results suggested that th is bioassay may be useful for selection in pollen before pollination.