The objective of this study was to identify the pathogen and biological control of pole rot on flue-cured tobacco, which causes damage losses during the yellowing stage of leaf curing in several counties of Dali Bai Autonomous Prefecture of Yunnan Province, China.

Infected tissues were used for isolating the causal agent classified by combining results from the morphology and multiple gene sequence analysis. Antagonistic activities of bacteria against the pathogen were also evaluated in vitro and in vivo.

Two fungi obtained from infected poles and leaves were grouped into the Rhizopus genus based on morphological characteristics. Furthermore, all isolates shared high internal transcribed spacer region (ITS) sequence similarity with R. arrhizus subspecies arrhizus CBS 112.07(T). Similar results were also obtained from multiple sequence alignment and phylogenetic analyses using the ITS, actin (ACT), translation elongation factor 1-α (TEF), and the largest subunit of RNA polymerase II (RPB1) of all isolates. Above all, the pathogen causing pole rot of flue-cured tobacco in Dali is R. arrhizus. Besides, five antagonistic bacteria, including WY11, WYZ, 05-1205, 4-4 and Z002, had robust inhibition activities against the hyphal growth of R. arrhizus in vitro. Among these bacteria, Z002 and 05-1205 were selected for biological control efficiency tests in the barn and showed strong evidence to support them as potential biological agents with relative control efficiency of 96 % and 81 %, respectively.

It was concluded that the causal agent of tobacco pole rot during flue-curing in Dali Bai Autonomous Prefecture of Yunnan is R. arrhizus. Two antagonists showed robust inhibition activities against R. arrhizus in vitro and in vivo, which provide promising agents for controlling tobacco pole rot with high efficiency and low toxic measures.