Evaluation of transgenic rolABC citrange Troyer for growth habit and root-associated bacteria

With the aim of modifying growth habit, rolABC genes isolated from Agrobacterium rhizogenes were introduced into Troyer citrange determining reduction of plant height and of internodal length. In this work 23 transgenic and 5 wild-type self-rooted clones were checked for some aspect of root growth and of interaction with soil microbial community. Transgenic clones showed a higher incidence of hairy root as compared to control plants. To check the effect of transgenic clones on rhizosphere microbial community, soil adhering to the roots was sampled to detect number of colonies of root-associated bacteria and of fluorescent pseudomonads. Furthermore an innovative technique named Amplified Ribosomal DNA Restriction Analysis (ARDRA) was applied to reveal changes in ammonia oxidising bacteria through the analysis of DNA extracts from the soil. Consistent results were obtained for transgenic and wild-type plants with very few differences in the number of colonies and in the ARDRA profile. One of the transgenic clones was further propagated in order to investigate some enzymatic analysis. Interestingly, transgenic plants showed a higher content of phenolic compounds and higher activity of phenylalanine ammonia–lyase (PAL) and of peroxidase (PO) that suggest possible differences in behavior in response to stress.