The influence of Trichoderma species on Leptosphaeria maculans and L. biglobosa growth on agar media and in oilseed rape plants
Abstract: The ascomycetous fungi Leptosphaeria maculans and L. biglobosa cause stem canker of crucifers – one of the most damaging diseases of oilseed rape in Poland and worldwide. The pathogens are responsible for major yield losses, which can be economically significant especially in the areas of intensive rapeseed cultivation in Europe, Australia and Canada. The pathogens are observed every year, with a higher proportion of L. maculans in West Europe and predominance of L. biglobosa in Central and East Europe. The disease is controlled with chemical sprays applied mostly in autumn. At many locations and years one autumn spray is insufficient to fully control the disease. Recently, great efforts are undertaken to study the possibility of biological control using antagonistic and hyperparasitic fungal species. It is postulated to use their potential to combat plant pathogens and use these organisms in integrated pest management technologies to reduce the amount of pesticides introduced to environment.The aim of this work was to examine possibilities of biological control of L. maculans and L. biglobosa using hyperparasites from the genus Trichoderma obtained from oilseed rape and yellow lupine plants as well as from soil. Tested isolates belonged to T. atroviride, T. hamatum, T. harzianum, T. koningii and T. longibrachiatum. The experiments were performed under laboratory conditions using dual cultures as well as under glasshouse conditions using oilseed rape plants.Trichoderma isolates caused significant decrease of growth rate, especially of L. biglobosa. On the other hand L. maculans showed antibiosis activity and caused decreased growth rate of T. longibrachiatum. The species of Trichoderma differed in their hyperparasitic effects towards Leptosphaeria spp. The highest decrease of Leptosphaeria spp. growth rate was caused by T. atroviride. Covering of cotyledons with Trichoderma spores was proved to serve as protective treatment against Leptosphaeria species. The influence of isolates from oilseed rape was significantly greater than the one originating from lupine.