Evaluation of antagonistic potential of some isolates of bacteria and Trichoderma spp. in the control of Zymoseptoria tritici causal agent of wheat leaf spot
The aim of this study is to develop a bio-control method against Zymoseptoria tritici blotch (STB) which is a leaf disease caused by the fungus Zymoseptoria tritici in wheat. This disease in one the main diseases of wheat in Morocco. 120 isolates of bacteria and 70 isolates of Trichoderma spp. of various ecological and geographical origins, were tested in vitro for their antagonistic potential towards two strains of Zymoseptoria tritici, namely G1-1 which was isolated from soft wheat (Triticum aestivum L.) and A5-1 which was isolated from durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.). Compared to the controls, all the antagonists selected after the in vitro tests (9 bacterial strains and 18 Trichoderma spp. isolates) showed a very high antagonism potential, generating zones of inhibition of the radial growth of Zymoseptoria tritici, which ranged from 34 to 84 % for the bacterial strains and from 40 to 70 % for the Trichoderma spp., after 96 hours of confrontation. To confirm the performance of the selected isolates in vitro, an in vivo assay on inoculated potted plants by the pathogen was conducted using two sensitive wheat varieties to septoria disease; ‘Aguilal’ (soft wheat variety) and ‘Karim’ (durum wheat variety). Spraying of selected antagonists suspensions onto leaf surfaces of wheat plants proved to be effective and significantly reduced the severity of the septoria disease up to 91 % in the preventive treatments. For curative treatments, the intensity of disease was more important. The symptoms were reduced from 7 to 72 % in the case of bacterial treatments and from 19 to 81 % for Trichoderma spp. strains.
Keywords: Zymoseptoria tritici, Trichoderma spp., Bacteria, biological control, wheat.