Saprophytic bacteria, yeasts and filamentous fungi were isolated from
Geraldton waxflower flowers and screened to identify potential antagonism
towards Botrytis cinerea. Isolates from other sources
(e.g. avocado) were also tested. Isolates were initially screened
in vitro for inhibition of
B. cinerea conidial germination, germ tube elongation
and mycelial growth. The most antagonistic bacteria, yeasts and fungi were
selected for further testing on detached waxflower flowers. Conidia of the
pathogen were mixed with conidia or cells of the selected antagonists,
co-inoculated onto waxflower flowers, and the flowers were sealed in glass
jars and incubated at 20˚C. The number of days required for the pathogen
to cause flower abscission was determined. The most antagonistic bacterial
isolate, Pseudomonas sp. 677, significantly reduced
conidial germination and retarded germ tube elongation of
B. cinerea. None of the yeast or fungal isolates tested
was found to significantly reduce conidial germination or retard germ tube
elongation, but several significantly inhibited growth of
B. cinerea. Fusarium sp.,
Epicoccum sp. and Trichoderma spp.
were the most antagonistic of these isolates. Of the isolates tested on
waxflower, Pseudomonas sp. 677 was highly antagonistic
towards B. cinerea and delayed waxflower abscission by
about 3 days. Trichoderma harzianum also significantly
delayed flower abscission. However, as with most of the fungal antagonists
used, inoculation of waxflower flowers with this isolate resulted in unsightly
mycelial growth.
Ethylene- and dark-induced flower abscission in potted Plectranthus: Sensitivity, prevention by 1-MCP, and expression of ethylene biosynthetic genes
