2 Index ABSTRACT ............................................................................................................................. 4 INTRODUCTION ......................................................................................................... 5 Prunus persica L. Batsch ........................................................................................... 5 Taxonomy and biology ......................................................................................... 5 GF 677 rootstock .................................................................................................. 5 The transport of water in plant ............................................................................. 6 Climate change ........................................................................................................... 7 The reuse of wastewater in agriculture ...................................................................... 9 The irrigation water .............................................................................................. 9 Wastewater cleaning treatment............................................................................. 9 Wastewater in agriculture ................................................................................... 12 The problem of bacterial contamination .................................................................. 16 Biology of enteropathogenic bacteria ................................................................. 16 The sources of contamination ............................................................................. 17 Overview of outbreaks associated with fresh products ...................................... 18 Internalization of pathogenic enterobacteria in plants ............................................. 19 Interactions between human enteropathogens and cultivated plants .................. 19 Colonization of the plant's surface ..................................................................... 19 The mechanisms of internalization ..................................................................... 20 Interaction between enterobacteria and the tree crops ....................................... 21 OBJECTIVE OF THE STUDY ................................................................................... 23 MATERIALS AND METHODS ................................................................................. 24 Tests carried out in the field ..................................................................................... 24 Experimental set up ............................................................................................ 24 Water chemical analysies ................................................................................... 25 Allometry measurements .................................................................................... 25 Water relations.................................................................................................... 25 Microbiological analyses .................................................................................... 26 Tests carried out in a controlled environment .......................................................... 28 3 Biological material and environmental condition .............................................. 28 Experiment 1 – Preliminary evaluation of inoculum influence on internalization of avirulent strain DH5 α-gpf ..................................................................................................... 29 Experiment 2 - Systemic colonization of the host plant upon E. coli inoculation 30 RESULTS .................................................................................................................... 31 Tests carried out in the field ..................................................................................... 31 Vegetative growth .............................................................................................. 32 Water relations (Stem water potentials) ............................................................. 34 Microbiological analysis .................................................................................... 36 Tests carried out in a controlled environment .......................................................... 37 Test E. coli in cut plants ..................................................................................... 38 Test E. coli in rooted plants ................................................................................ 39 Test E.coli survival after 35 days ....................................................................... 41 Discussion ................................................................................................................ 41 CONCLUSIONS .......................................................................................................... 45 REFERENCES ............................................................................................................ 46 RINGRAZIAMENTI ................................................................................................... 58