Biocontrol projects
In the past few years, the production of cereals, particularly wheat, and of oilseed rape has boosted in several countries in Europe with the consequence of closer crop rotation systems. Concomitantly, we have seen a significant change in the soil tillage systems towards minimum or no tillage resulting in a reduced incorporation of plant residues in the soil after harvest. As plant residues play a crucial role in the life cycle of many fungal pathogens the actual agricultural practice has given rise to the occurrence of several notorious diseases. Plant debris represent the substrate for formation of fruiting bodies like perithecia, pseudothecia and asexual pycnidia, or sclerotia. Fruiting bodies release ascospores or conidia which infect the developing crop plants. In most cases yield losses resulting from plant diseases can be mitigated by the use of fungicides. However, these fungicides only protect the plant from being attacked by ascospores and conidia, but do not reduce the causal inoculum residing on crop debris in the field. In the 1990s Microsphaeropsis ochracea, a coleomycete (Fig. 1) has been isolated from dead apple leaves in Canada. This fungus showed an antagonistic potential against Venturia inaequalis the causal agent of apple scab. By spraying conidia of Microsphaeropsis ochracea in the apple orchards a quite effective reduction of the ascospore production by Venturia inaequalis was achieved (Carisse & Bernier, 2002). Further, it was shown that Microsphaeropsis ochracea may reduce the sclerotia germination of Botrytis squamosa and Rhizoctonia solani (Carisse et al. 2001; Carisse et al. 2006). In addition, Microsphaeropsis ochracea showed an antagonistic effect against Gibberella zeae, the fusarium head blight fungus of cereals (Bujold et al. 2001). Based on these encouraging results we currently investigate whether Microsphaeropsis ochracea could serve as a broad-spectrum biological control agent against important straw-borne fungal pathogens in wheat (Mycosphaerella graminicola, Pyrenophora tritici-repentis, Fusarium spp.), and in oilseed rape (Leptosphaeria maculans, Verticillium longisporum). We are running field and greenhouse experiments with the following primary objectives: - Characterisation of the antagonistic potential of Microsphaeropsis ochracea against straw-borne pathogens in different soil depths - Impact of environmental factors and different application rates of the antagonist on the antagonistic action - Microscopic and biochemical investigations on the interaction of Microsphaeropsis ochracea with the fruiting bodies or resting structures of the pathogens involved Preliminary results have demonstrated a broad efficacy of M. ochracea against conidia of species such as Pyrenophora teres, Bipolaris sorokiniana, Leptosphaeria maculans and Verticillium longisporum (Fig. 2). Inhibition rates for conidial germination in vitro were above 95% after co-cultivation for 7 to 14 days. Similarly the formation of microsclerotia by V. longisporum was inhibited. The antagonistic efficacy of M. ochracea in unsterile conditions awaits further investigation. This study is funded by the German Ministry of Agriculture and Consumer Protection and conducted in collaboration with the Prophyta company in Malchow/Poel (www.prophyta.com). Investigators: Stefanie Nehrlich, Nana Bitsadze, Martin Stadler Supervisor: Prof. Andreas von TiedemannBiological degradation of straw-borne fungal pathogens of cereals and oilseed rape by the fungal antagonist Microsphaeropsis ochracea
Selected publications