New Bacterial Disease of Lobelia erinus Cultivar Richardii Caused by Xanthomonas campestris. G. Poschenrieder, Bayerische Landesanstalt für Bodenkultur und Pflanzenbau, Voettingerstr, 38, D-8050 Freising. E. Lohweg, W. W. P. Gerlach, and J. D. Janse. Staatliche Versuchsanstalt für Gartenbau Weihenstephan, Institut für Botanik und Pflanzenschutz, D-8050 Freising 12, West Germany; and Plantenziektenkundige Dienst, Geertjesweg 15, NL-6700 HC Wageningen, Netherlands. Plant Dis. 74:252. Accepted for publication 5 December 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0252C.
A leaf blight and dieback of Lobelia erinus L. 'Richardii' was noticed
in 1988 in a commercial nursery near Munich, West Germany (1).
The disease later appeared in other glasshouse units io Germany and
in 1989 was found in a greenhouse in the Netherlands containing
plants obtained from Great Britain. Losses within individual houses
ranged from 3O to 100%. Symptoms began as a water-soaking, followed
by chlorosis of leaf bases and adjacent areas on the stems. These
areas became necrotic, leading to death of acropetal portions of the
stem. Watcr-sosking and chlorosis initiated at leaf tips were followed
by necrosis that developed interveinally. Occasionally, droplets of
bacterial ooze were seen. Gradually the plants died, especially those
that were watered overhead. Isolations from diseased tissue as well
as symptomlrss plantd conistently yielded only a yellow bacterium.
Based on results of standard physiological and biochemical tests, as
well as fatty acid analysis, the baclerium was identified as a new
pathovar of Xanthomonas campestris (Pammel) Dowson. Spray
inoculations of the: causal bacterium (1 X 108 cfu/ml) onto healthy
seedlings reproduced the symptoms secn on naturally infected plants.
The suspect pathogen was reisolated from tbe inoculated plants, which
died within 4 wk. The bacterium was pathogenic to artificially
inoculated L fulgens L. 'Queen Victoria' plants. but tbe only symptom
was severe stunting. This is the first report of a disease in Lobelia
causcd by a pathovar of X. campestris.