Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2017
Publication Date: 5/1/2018
Citation: Schlatter, D.C., Burke, I., Paulitz, T.C. 2018. Succession of fungal and oomycete communities in glyphosate-killed wheat roots. Phytopathology. 108:582-594.
Technical Abstract: Dying roots of herbicide-killed weeds or volunteer plants can foster an increase in plant pathogens, such as Rhizoctonia and Pythium spp. and serve as a ‘greenbridge’ for pathogens infecting subsequent crops. To investigate the succession of fungal and oomycete communities after herbicide sprays, we tracked the communities in live wheat roots and killed roots following termination with Roundup (glyphosate) or SelectMax (clethodim). DNA was extracted from washed roots collected prior to herbicide application and at 3 days, 1 week, 2 weeks, and 3 weeks post-application. Fungal and oomycete ITS1 regions were PCR-amplified and sequenced (Illumina MiSeq). Fungal and oomycete communities varied significantly with sampling time and herbicide type. Myrmecridium sp. dominated fungal communities in roots at most time points in live and killed roots, but saprophytic species began to replace this taxon in herbicide-treated roots by three weeks. Pythium volutum and Lagena radicola dominated oomycete communities. P. volutum increased and L. radicola decreased in relative abundance after termination with glyphosate, but remained relatively stable in live roots or those killed with clethodim. Fungal and oomycete richness decreased over time in glyphosate-killed roots, but was relatively stable in other treatments. Oomycete pathogens in wheat roots quickly multiply after herbicide treatments, and saprophytic taxa displace pathogens over time.