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Using naturally occurring endophytic fungi or bacteria associated with wheat as a biological control agent against the cereal cyst nematodes, Heterodera species
Project
Project code: JKI-EP-08-2228
Contract period: 01.01.2013
- 31.12.2017
Purpose of research: Applied research
Keywords: plant protection, wheat, Heterodera spp.
Cereal cyst nematodes (Heterodera spp.) are causing significant losses in wheat, especially in North Africa and West Asia. Recently, fungal hyphae associated with nematodes were found in trial fields of CIMMYT in Turkey. These findings were correlated with strongly reduced nematode cyst numbers. The main aim of the current project is therefore to isolate endophytes of wheat plants of this site, to characterise the isolates using molecular systematic methods and to test their antagonistic effects on the nematodes. Field observations in experimental wheat fields of CIMMYT in Turkey revealed a sharp decline of the final nematode populations in terms of cyst numbers of H. filipjevi in two consecutive years. Microscopic observations of the cyst samples of these final nematode populations frequently revealed the presence of fungal structures, mostly in young gravid females of H. filipjevi. We thus hypothesized that the observed fungi or other microorganisms, like bacteria, might have played an important role in the reduction of the nematode population. Therefore, the present project was conducted to (1) isolate and identify microorganisms that could potentially lead to soil suppressiveness against H. filipjevi in the experimental wheat fields of CIMMYT in Turkey, (2) evaluate the potential biocontrol impacts of the nematode-associated fungal and bacterial isolates, and (3) establish an improved screening system for nematode-parasitic fungi in nematode-suppressive soils. In the first screening considered as ‘general screening’, 100 fungal and 63 bacterial isolates were obtained from the cysts or wheat roots of H. filipjevi. The biocontrol potential of fungal and bacterial isolates was evaluated against the CCN H. filipjevi under controlled conditions in a growth chamber. All fungal isolates were identified using light microscopy and molecular phylogenetic analyses. The most frequently isolated fungi were Fusarium spp., Pochonia chlamydosporia, Acremonium spp. and Paecilomyces spp. Of the fungal isolates tested against nematodes, the ten isolates showing the highest biocontrol potential reduced the final nematode populations by about 35 to a maximum of 50%. These isolates belong to the following species: Pochonia chlamydosporia, Paecilomyces fumosoroseus, Acremonium persicinum, Gliomastix murorum and Fusarium acuminatum, with P. chlamydosporia being the most effective. Of the bacterial isolates evaluated against H. filipjevi, the first ten isolates showing highest biocontrol potential were selected and molecularly identified. Of these, nine isolates were identified as Bacillus spp. and one species belonged to the genus Enterobacter. The antagonistic in vivo screening of bacterial isolates against H. filipjevi reduced the nematode population by a maximum of ca. 30%. In further screenings here coined as ‘focused screening’, nematode eggs that based on microscopic screening seemed to be infected by fungi were examined. More than 50 fungal isolates were obtained from these visually selected infected eggs of field-collected cyst samples. Molecular characterisation of these isolated fungi indicated a wide variety of ascomyceteous species and five so-far undescribed fungal species belonging to the Hypocerales, Helotiales and Pleosporales. These are currently in the process of being described. Metabolite profiling of secondary compounds of selected fungal strains with a high control potential and the undescribed fungal species has been started in collaboration with the Helmholtz Centre for Infection Research (HZI). One compound new for the fungal family Bionectriaceae and one completely new compound belonging to the antihelminthic Cyclooctadepsipeptides have so far been elucidated. In summary, the results showed a high diversity of fungal species that are seemingly specifically associated with CCN and suggest that nematode cysts and eggs constitute a rich source of nematode-parasitic fungi that should further be assessed for their biocontrol potential against CCN.
Section overview
Subjects
- Crop Production
- Crop Protection
Framework programme
Funding programme
Excutive institution
Institute for Epidemiology and Pathogen Diagnostics (JKI-EP)
