Infection Process of Burkholderia glumae Before Booting Stage of Rice

Abstract

Burkholderia glumae is a well‐known pathogen for causing bacterial panicle blight of rice. In this study, the infection process of B. glumae in rice plants at different growing stages was tracked by means of real‐time fluorescence quantitative PCR. Burkholderia glumae tended to colonize at the growing point of rice plants, and the biomass of population was 104 to 108 CFU/g. The most intensive colonization was detected in the upmost leaf in the two‐leaf period. However, after the two‐leaf period, the population of pathogens decreased significantly, and they successfully recovered in the booting stage and broke out in panicles. We also illustrated the incubation location of B. glumae by presenting the infection pattern in the seedling and tillering stage of rice. Under fluorescent microscopy, the gfp‐labelled pathogens were first found in the vascular bundle of lateral roots, taproots and injured cells, then they were observed in the root hairs, epidermal cells and main root cap. The pathogens in the vascular bundle laterally dispersed towards the epidermal cells. By spray application of a bacterial suspension, the pathogens landed on the leaf sheaths and leaves, colonized in the epidermal hairs and leaf hairs, or invaded into the cells through the stomas. At the same time, the pathogens from the vascular bundle of the roots spread into the vascular bundle of leaf sheaths and leaves, which caused the leaves to curl and wilt, beginning from the tip.

Infection Process of Burkholderia glumae in Rice Spikelets

“…In our previous study, B. glumae acted as endophytic bacteria in the tillering stage of rice, and the biomass of population was about 10 5 CFU/g (Li et al. ). Obviously, the infection in panicles was rapider than in other tissues.…”

“…The preparation of templates and procedures of real‐time fluorescence quantitative PCR were described in our previous study (Li et al. ). The cycle threshold ( Ct ) value would be shown in an FX96 Real‐Time PCR System (Bio‐Rad, Munich, Germany).…”

“…To detect the bacterial content in different parts of spikelets, stamens and gynoecia were peeled off. The preparation of templates and procedures of real-time fluorescence quantitative PCR were described in our previous study (Li et al 2016). The cycle threshold (Ct) value would be shown in an FX96 Real-Time PCR System (Bio-Rad, Munich, Germany).…”

“…In a previous study, a gfp ‐labelled B. glumae was used to clarify the infection pattern before the booting stage of rice (Li et al. ). In this study, we constructed a gfp ‐labelled system and described the infection pattern in rice spikelets.…”

“…Both metabolically active and starving bacterial cells can be detected by the expression of the GFP marker (Unge and Jansson 2001;Campos-Soriano and Segundo 2009). In a previous study, a gfp-labelled B. glumae was used to clarify the infection pattern before the booting stage of rice (Li et al 2016). In this study, we constructed a gfp-labelled system and described the infection pattern in rice spikelets.…”