Production and transformation of conidia of Venturia inaequalis

High yields of conidia of Venturia inaequalis were produced from either mycelial fragments or conidia on cellophane-covered surfaces of agar media incubated under continuous near-ultraviolet light. Optimal conditions required a cellophane-covered surface of potato-dextrose agar in combination with light and incubation for 1 wk. The procedure represents a convenient techique for the mass-production of clonal and sterile V. inaequalis conidia. Conidia were biolistically transformed to hygromycin B resistance with a plasmid (pOHT) containing a bacterial phosphotransferase gene spliced between regulatory elements from Aspergillus nidulans. Southern hybridization analysis showed that the plasmid was incorporated into heterologous regions of the genome. Hygromycin B-resistant transformants were mitotically stable during nonselective propagation. The heterologous gene conferring hygromycin B resistance was expressed during early stages of conidia germination and during vegetative growth of mycelium