Selection and identification of a tobacco endophytic bacteria strain L1 with inhibitory effect against TMV
The objective of this study is to screen a biocontrol bacterial strain with significant inhibitory effect against TMV (Tobacco mosaic virus). The strains were isolated from leaves of tobacco var. Luyan 1 resistant to TMV. The anti-TMV strain was tested by half-leaf method on hypersensitive plants of N. tabacum var. Samsun and identified by the morphology, physiological and biochemical tests and sequence analysis of 16S rDNA. The effect of the bacterial strain on the virus particle was firstly observed in liquid fermentation and transmission electronic microscope. The results were also verified by SDS-PAGE analysis. Additionally, indoor pot tests were conducted with three treatments. (I) The fermentation liquid was firstly sprayed on NC89 leaves 24 h before inoculating the virus to NC89. (II) Virus was inoculated to NC89 24 h before spraying fermentation liquid. (III) The mixture was inoculated to NC89 after the fermentation liquid with virus juice for 30 min. Six strains with an inhibitory effect against TMV were screened from 53 endophyte strains. The pot test results showed that the antiviral rate of strain L1 was 82.61% and further study was required. Strain L1 was gram-negative and identified as Alcaligenes faecalis. It was observed that Alcaligenes faecalis L1 could disperse TMV particles and disrupt the particles into small fragments. However, strain L1 could not affect the coat protein of TMV based on SDS-PAGE analysis. The pot test results showed that strain L1 could achieve ideal TMV control efficiency with inhibition rate of treatment I, II and III of 34.58%, 21.81% and 82.81%, respectively. The selected strain L1 could be used as an antiviral agent for future study and application.