Improved Methods for Inducing Sporulation of Pyrenochaeta lycopersici. D. M. McGrath, Graduate Research Assistant, Department of Plant Pathology, University of California, Davis 95616. R. N. Campbell, Professor, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 67:1245-1248. Accepted for publication 18 May 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1245.

Factors affecting sporulation of Pyrenochaeta lycopersici obtained from tomato roots in 1980 and 1981 were studied. V-8 juice agar medium (V8A) was superior to 18 other media. Sporulation was enhanced by short incubation (3–4 days) of recent isolates on water agar before transfer to V8A, whereas isolation from diseased tomato roots directly onto V8A gave nonsporulating colonies. The optimum pH for sporulation was about 5.5. Light was required; fluorescent cool-white lamps were as effective as fluorescent BLB black light lamps, and constant exposure was superior to 12- or 8-hr photoperiods. The optimum temperature range for sporulation was 20–24 C. Isolates maintained for 2 yr on V8A by conidial transfer remained sporogenic and pathogenic. Conidia may be useful for testing resistance of seedlings.