Tiered Temperature System for Producing and Storing Conidia of Peronosclerospora sorghi. Jeweus Craig, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843. Plant Dis. 71:356-358. Accepted for publication 22 October 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/PD-71-0356.

A system was devised for producing and preserving conidia of Peronosclerospora sorghi for use as inoculum. The procedure used natural forces to transfer mature conidia produced on diseased sorghum leaves to water agar chilled to temperatures that inhibited conidial germination. Conidia produced by production-storage intervals (time interval between incubation of diseased leaves and collection of conidia from agar surface) of 16 and 24 hr and agar temperatures of 3 and 5 C germinated after collection at frequencies ranging from 81 to 92% with no significant differences between storage intervals or temperatures. Germination of conidia produced by a 32-hr production-storage interval was less, ranging from 41 to 57%. Conidial inoculum produced by a 24-hr production-storage interval induced a 99% incidence of downy mildew in susceptible corn seedlings. The system permits greater flexibility in the timing of inoculum production and inoculation than older methods.