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The search for novel antimicrobial agents to be used for plant protection has prompted us to design analogues incorporating non-natural amino acids. Herein, we designed and synthesized cyclic peptidotriazoles derived from the lead antimicrobial cyclic peptide c(Lys-Lys-Leu3-Lys-Lys5-Phe-Lys-Lys-Leu-Gln) (BPC194). In particular, Leu3 and Lys5 were replaced by a triazolyl alanine, a triazolyl norleucine or a triazolyl lysine. These peptides were screened for their antibacterial activity against Xanthomonas axonopodis pv. vesicatoria, Erwinia amylovora and Pseudomonas syringae pv. syringae, for their hemolysis and for their phytotoxicity. Results showed that the type of triazolyl amino acid and the substituent present at the triazole influenced the antibacterial and hemolytic activities. Moreover, the position of this residue was also crucial for the hemolysis. The lead compounds BPC548 and BPC550 exhibited high antibacterial activity (MIC of 3.1 to 25 μM), low hemolysis (19 and 26% at 375 μM, respectively) and low phytotoxicity. Therefore, these analogues could be used as new leads for the development of effective agents to control pathogenic bacteria responsible for plant diseases of economic importance This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) [grant numbers AGL2009-13255-C02-02/AGR and AGL2012-39880-C02-02]

S. V. was recipient of a predoctoral fellowship from the Generalitat de Catalunya. This work was supported by the Spanish Ministerio de Economia y Competitividad (MINECO) (grant numbers AGL2009-13255-C02-02/AGR and AGL2012-39880-C02-02)

S. V. is a recipient of a predoctoral fellowship from the Generalitat de Catalunya. This work was supported by grants from the Spanish Ministerio de Economia y Competitividad (MINECO) (AGL2009-13255-C02-02/AGR and AGL2012-39880-C02-02)

Cyclic peptidotriazoles derived from the antimicrobial cyclic peptide c(Lys-Lys-Leu-Lys-Lys-Phe-Lys-Lys-Leu-Gln) (BPC194) were prepared by incorporating a triazolyl amino acid at the 3-position. The synthesis was accomplished on solid-phase and involved as the key step a copper-catalyzed cycloaddition reaction between a resin-bound alkyne or a resin-bound azide and a range of azides or alkynes in solution, respectively. This methodology was also applied to the synthesis of a conjugated peptide containing a cyclic and a linear peptidyl sequence linked through a triazolyl ring. Cyclic peptidotriazoles were obtained in excellent purities starting either from an alkynyl or an azido peptidyl resin. These compounds were screened in vitro for their growth inhibition of bacterial phytopathogens and for their cytotoxic effects on eukaryotic cells. Peptide sequences with high antibacterial activity and low hemolysis were identified, constituting good candidates for the design of new antimicrobial agents.

The effect of strains EPS291 and EPS817 of Pseudomonas fluorescens to improve plant growth and nutrition as well as to reduce root-knot nematode in roots was investigated in micropropagated banana. Plantlets, cultured under commercial nursery conditions, were treated twice with bacteria after transplanting from in vitro conditions. Bacterial application was performed by drenching bacterial suspension containing approximately 10 8 CFU (colony-forming units) g -1 of substrate. Both strains significantly increased aerial fresh weight, plant length and leaf area, while the effect on other growth parameters depended on the strain. N content was also significantly increased after both bacteria treatments. A second experiment was performed to determine the potential biocontrol effect against the root-knot nematode Meloidogyne javanica. Following the same experimental conditions, Meloidogyne inoculum containing 10 500 nematodes was applied 15 days after the second bacteria treatment. At the end of the experiment, 135 days later, nematode reproduction in roots of bacterised bananas was significantly reduced. In both experiments, the inoculated bacteria colonised the root system and population levels in root, 5.5 months after transplanting were 6.8 x 10 3 to 1.6 x 10 4 CFU g -1 fresh weight of root. The potential use of this technology to improve hardening stages in banana plant production in commercial nurseries is discussed.

highest counts recorded for fruits and sprouts respectively. The highest incidence level of coliforms was found in ready-to-eat vegetables, with up to 65.7% of samples containing from 5 to 9 log10CFU g −1 . Yeasts and moulds showed their highest incidence level between 5 and 6 log10 CFU g −1 , with an overall range from < 2t o 9l og10 CFU g −1 . Salmonella spp., Listeria spp. and L. monocytogenes were detected in 0.67, 2.7 and 0.9% respectively of the total samples examined. CONCLUSION: The samples analysed can be gathered into two main groups, one showing low microbial counts (fruits) and a second group (raw whole leaves and roots and packed ready-to-eat vegetables) with higher microbial contamination. Although incidence levels of pathogenic bacteria reported here are in the lower range of those reported elsewhere, positive detections highlight the importance of good hygienic measures throughout the whole food chain.  2007 Society of Chemical Industry