Inoculation and tracking of beneficial microbes reveal they can establish in field-grown potato roots and decrease blemish diseases

In a three-year field study, we inoculated two potato varieties with a selection of four beneficial microbial strains (i.e. Rhizophagus irregularis MUCL41833, Trichoderma asperelloides A, Pseudomonas brassicacearum 3Re2-7 and Paraburkholderia phytofirmans PsJN), alone or in combination. Plants were grown under rainfed or irrigated conditions, and potato yield and development of several diseases were evaluated. The microbial inoculants were traced in the root system at different stages of crop development via molecular markers. Whatever the water supply, the inoculants had no effect on yield. Conversely, some of the inoculants were able to lower the incidence and/or severity of several blemish diseases, namely common scab-associated symptoms (CSAS) and silver scurf/black dot-associated symptoms (SSAS). Microbial consortia were more efficient in decreasing symptoms compared to single strain inoculations. The best control was obtained with the combination of R. irregularis and P. brassicacearum, which reduced the incidence of CSAS by 22% and severity of SSAS by 21%. Root tracking revealed that P. brassicacearum and P. phytofirmans PsJN were able to establish in the root system of the potato, while only P. brassicacearum was detected from emergence until flowering of the plants.