Environmental Influences on the Establishment of Puccinia recondita Infection Structures. M. G. Eversmeyer, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Department of Plant Pathology, Kansas State University, Manhattan 66506. C. L. Kramer, and Z. M. Hassan. Professor, Division of Biology, and Former Graduate Student, Division of Biology, Kansas State University, Manhattan 66506. Plant Dis. 72:409-412. Accepted for publication 14 December 1987. 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, 1988. DOI: 10.1094/PD-72-0409.

Optimum temperature for completion of the infection process (as measured by the development of infection structures: appressoria, substomatal vesicles, and infection hyphae with at least one haustorium) by urediniospores of Puccinia recondita was 16 C. At 16 C, 39% of the urediniospores germinated within approximately 1 hr after inoculation, 35% of the germinated spores formed appressoria in approximately 3 hr, 50% of the appressoria formed substomatal vesicles within approximately 8 hr, and 50% of the substomatal vesicles formed infection hyphae with at least one haustorium in approximately 12 hr. Infection structures developed much slower at temperatures above or below 16 C. The minimum length of dew period for trace infection (one uredinium per leaf) was 3 hr at 16 C and 4 hr at temperatures above or below 16 C. Penetration and infection (development of substomatal vesicles and infection hyphae with haustoria) increased with increasing dew period. Light intensity provided by 40W cool-white VHO fluorescent lights reduced spore germination during the first 3 hr of incubation on both water agar and leaf surfaces but failed to inhibit germination completely. As a result, rate of development of infection structures was slower in the light than in the dark.

Keyword(s): modeling, wheat, wheat leaf rust.