Characterization of Growth and Sclerotial Production of Sclerotinia minor Isolated from Peanut in Texas. K. E. Woodard, Texas Agricultural Experiment Station, Stephenville 76401. C. E. Simpson, Texas Agricultural Experiment Station, Stephenville 76401. Plant Dis. 77:576-579. Accepted for publication 8 February 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0576.

Five isolates of Sclerotinia minor (Behrens, Charlotte, Dirk, Eppler, and TAES#1) were collected from diseased peanut (Arachis hypogaea) plants obtained from four commercial peanut production areas in Texas. The isolates were grown on potato-dextrose agar (PDA), cornmeal agar (CMA), and Czapek-Dox agar (CDA) in a controlled environment at temperatures ranging from 0 to 36 C in 2-degree increments. The optimum temperature for radial mycelial growth (RMG) of each isolate varied with the growth medium. Optimum RMG occurred at 24–26 C on PDA for the five isolates and at 18–22 C on CMA and CDA. RMG of all isolates on PDA was about double that on CMA or CDA at the optimum temperature and in the mid-temperature range. Optimum sclerotial production on PDA occurred at 20–24 C for all five isolates, with a high of 1,219 sclerotia of Eppler per 9-cm culture plate at 24 C. The maximum sclerotial production on CMA was 68 per 9-cm plate for Eppler at 26 C; the other isolates produced their maximum numbers of sclerotia at 18 or 22 C. The maximum sclerotial production on CDA was 212 per 9-cm plate for Dirk at 20 C; sclerotial production peaked in the 18–20 C range in three of the isolates but at 26 C in the other two isolates. The maximum weight of sclerotia produced on PDA per 9-cm petri dish occurred in isolates grown at 22 C for all isolates except Behrens, which reached its maximum sclerotial weight at 28 C. The maximum weight of sclerotia on CMA occurred at different temperatures in the 18–28 C range for all isolates. For four of the five isolates, the maximum sclerotial weight on CDA occurred in the 6–12 C range. Sclerotia produced on any medium at temperatures of 14–26 C generally had 50–100% myceliogenic germination on water agar at 21 C.