Temperature Dependent Germination and Host Penetration of the Entomophthoralean Fungus Zoophthora Radicans on the Leafhopper Empoasca Kraemeri

Document Type

Article

Journal/Book Title/Conference

Mycological Research

Volume

96

Issue

1

Publication Date

1-1-1992

First Page

38

Last Page

48

Abstract

Zoophthora radicans primary and secondary ovoid conidia inoculated onto Empoasca kraemeri fifth-instar nymphs germinated in three alternative modes, forming either germ-tubes, capilliconidiophores or replicative conidiophores. Production of germ-tubes was positively correlated, and production of capilliconidiophores inversely correlated, to temperatures over 5–32°C. Significant numbers of replicative conidiophores were produced only at 25–30°. The temperatures inducing the fastest rates of germination as capilliconidiophores, germ-tubes, and replicative conidiophores were 16·5, 22, and 26°, successively. Germ-tube formation was the most rapid mode of germination, occurring in ca 0·7 h at 22°; germination as capilliconidiophores or replicative conidiophores required 1·9 and 3·2 h, respectively, under optimal temperature conditions. Total germination (all modes combined) was optimum at 22°. High-temperature inhibition of germination was evident at 28° and severe at 30°; however, most germ-tubes produced at these temperatures were able to complete the processes of appressorium formation and penetration of the host cuticle. At 32°, only 6% of conidia germinated and no appressoria were produced. AT 10, 20, and 25°, 40, 20, and 4%, of all penetrations, successively, originated from capilliconidia produced by the ovoid conidia. The optimum temperature for infection (23°) was found to be similar to the optimum for vegetative germination (22°). The median time from inoculation to infection of the leafhoppers at 23° was 5.6 h. At temperatures near the upper threshold, lack of germination of the inoculum was the most important factor limiting host infection.

This document is currently not available here.

Share

COinS