红色荧光蛋白(RFP)标记法揭示烟草野火病菌侵染根系的新途径OA

To clarify the root invasion pathway of the tobacco wildfire pathogen Pseudomonas amygdali pv.tabaci,tobacco seedlings at the two-true-leaf and five-true-leaf stages were inoculated by the root-dip method,and the infection and colonization of the pathogen were observed using confocal laser scanning microscopy.In addition,tobacco seedlings were inoculated by the root-irrigation method,and the number of pathogens in roots,stems,and leaves was isolated and quantified using the dilution plating method.The results showed that 24 h after root-dip inoculation,P.amygdali pv.tabaci accumulated in the root tip elongation zone,root hair zone,and the junction between lateral roots and taproot.Meanwhile,the pathogen could also be observed inside the vascular bundle cells of roots and stems.From one to ten days after inoculation,the bacterial population on the root surface gradually declined,whereas the bacterial population inside root tissues initially increased and then decreased.The bacterial population on the root surface reached a peak of 5.00 × 106 cfu/g on day one after inoculation,while the bacterial population inside root tissues reached a peak of 3.91×106 cfu/g on day five after inoculation.The inoculated pathogen could also be re-isolated from the roots,stems,and leaves of tobacco plants after root-irrigation inoculation.In addition,P.amygdali pv.tabaci was isolated from the roots,stems,and leaves of both asymptomatic and diseased tobacco plants in diseased fields,with bacterial populations ranging from 7.25 × 102 to 5.41 × 105cfu/g.These findings revealed a novel invasion pathway of the tobacco wildfire pathogen,namely root invasion followed by vascular bundle transmission,which eventually leads to leaf necrosis.Confirmation of this invasion pathway provides new insights for the prevention and control of tobacco wildfire disease.