A Rhizosphere-Derived Consortium of Bacillus subtilis and Trichoderma harzianum Suppresses Common Scab of Potato and Increases Yield

The ability of a rhizosphere-derived microbial product (composed of a consortium of a strain of Bacillus subtilis and a strain of Trichoderma harzianum) to suppress common scab disease in potato caused by Streptomyces spp. was examined over a two-year period. Relative to the condition in which 0 kg·ha(−1) of the designated microbial product was applied (control), the disease index decreased by 30.6%–46.1%, and yield increased by 23.0%–32.2% in treatments in which 225 or 300 kg·ha(−1) of the microbial product was administered, respectively. The bacterial communities present in the rhizosphere were assessed at an early stage of tuber formation, a time at which tubers are susceptible to common scab. Potato plants in which soils were treated with 225 or 300 kg·ha(−1) of the microbial product harbored rhizospheric microbiota with lower α-diversity and an increased relative abundance of taxa representing the beneficial bacteria. In summary, a select microbial product composed of a consortium of Bacillus subtilis and Trichoderma harzianum effectively suppressed common scab disease and increased tuber yield by establishing a high relative abundance of beneficial bacteria in the rhizosphere.