We isolated bacteria and fungi from composted chicken, sheep, cow and horse manure and screened each isolate for their ability to suppress P. cinnamomi in dual-culture in vitro assays. Of the 180 isolates, including 31 actinomycetes, 64 fungi, 44 fluorescent pseudomonads and 41 endospore-forming bacteria, 45 isolates significantly inhibited the growth of P. cinnamomi on plates. The inhibitory microbes included 24 fungi (including Trichoderma sp., Gliocladium penicillioides and Fusarium sp.), 0 actinomycetes (all Streptomyces sp.), 7 fluorescent pseudomonads (Pseudomonas sp.) and 4 endospore-forming bacteria (Bacillus sp.). The most common mode of action observed was antibiosis, although mycoparasitism, indicated by parallel hyphal growth, hyphal coiling, appressorium formation and direct penetration, was also observed with one isolate of Trichoderma. These results help to explain the role of microbes in the suppression and biological control of P. cinnamomi by composted manures.
Full Text