Endophytic bacterial communities in tomato plants with differential resistance to Ralstonia solanacearum

Abstract

The endophytic bacterial communities in tomato varieties having differing resistance (or susceptibility) to Ralstonia solanacearum were investigated using both cultivation dependent and independent approaches. Both approaches revealed the differences between resistant (Xiahong-1) and susceptible (Baoshi-5) cultivars in terms of diversity and abundance of endophytic bacteria. The amount of the endogenous bacteria in Xiahong-1 at different growth stages was significantly higher than that in Baoshi-5. Furthermore, there were more culturable and antagonistic endophytic bacteria in Xiahong-1 than that in Baoshi-5. Seven endophytic bacterial genetic groups were identified in Xiahong-1 by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) and 16S rDNA sequence, and they were highly similar to Sphingomonas yanoikuya, Pseudomonas pseudoalcaligenes, Serratia marcescens, Bacillus megaterium, Paenibacillus polymyxa, B. pumilus and B. cereus. Four groups were identified in Baoshi-1 which were highly similar to S. yanoikuyae, Pseudomonasfluorescens, Arthrobacter globiformis and Paenibacillus polymyxa. In addition, antagonistic endophytes were identified by 16S rRNA gene analysis, and tested for their abilities to protect tomato plants from infection with R. solanacearum. The relationships between plant resistance and endophytic bacteria diversity are discussed.   Key words: Tomato, Ralstonia solanacearum, resistance, endophytic bacteria, diversity,biological control, 16S rRNA gene.