Growth and sporulation in vitro of Cercospora apii, Cercospora arachidicola, Cercospora kikuchii, and other species of Cercospora

Abstract

Cercospora apii Fres., Cercospora arachidicola Hori, and Cercospora kikuchii (Matsumoto & Tomoyasu) Gardn. were single spored, and the resultant colonies were characterized. All isolates of C. arachidicola were morphologically identical, whereas those of C. apii and C. kikuchii were either smooth or had radial folds. Variability in sporulation was also evident. Multiple-point inoculation of culture media in plates with conidia helped to overcome variability in the amount of conidial production. Maximum sporulation was obtained at 4 days with C. apii and C. kikuchii, and from 7 to 10 days with C. arachidicola. Single-point inoculation of a V-8 culture medium in plates from peripheral dark mycelial growth in potato dextrose agar (PDA) culture resulted in increased sporulation by C. kikuchii. Sporulation of C. kikuchii was maintained throughout a 15-month study by selective subculturing; however, conidial production decreased over time. A total of 15 other species of Cercospora sporulated within a week following a V-8 inoculation of culture medium in plates with mycelial agar blocks.