Changes in plant metabolism induced by dioxygenase inhibitors and their effect on the epiphytic microbial community and fire blight (Erwinia amylovora) control

Fire blight, caused by the gram negative bacterium Erwinia amylovora, is one of the most destructive bacterial diseases of Pomaceous plants. Therefore, the development of reliable methods to control this disease is desperately needed. This research investigated the possibility to interfere, by altering plant metabolism, on the interactions occurring between Erwinia amylovora, the host plant and the epiphytic microbial community in order to obtain a more effective control of fire blight. Prohexadione-calcium and trinexapac-ethyl, two dioxygenase inhibitors, were chosen as a chemical tool to influence plant metabolism. These compounds inhibit the 2-oxoglutarate-dependent dioxygenases and, therefore, they greatly influence plant metabolism. Moreover, dioxygenase inhibitors were found to enhance plant resistance to a wide range of pathogens. In particular, dioxygenase inhibitors application seems a promising method to control fire blight. From cited literature, it is assumed that these compounds increase plant defence mainly by a transient alteration of flavonoids metabolism. We tried to demonstrate, that the reduction of susceptibility to disease could be partially due to an indirect influence on the microbial community established on plant surface. The possibility to influence the interactions occurring in the epiphytic microbial community is particularly interesting, in fact, the relationships among different bacterial populations on plant surface is a key factor for a more effective biological control of plant diseases. Furthermore, we evaluated the possibility to combine the application of dioxygenase inhibitors with biological control in order to develop an integrate strategy for control of fire blight. The first step for this study was the isolation of a pathogenic strain of E. amylovora. In addition, we isolated different epiphytic bacteria, which respond to general requirements for biological control agents. Successively, the effect of dioxygenase inhibitors treatment on microbial community was investigated on different plant organs (stigmas, nectaries and leaves). An increase in epiphytic microbial population was found. Further experiments were performed with aim to explain this effect. In particular, changes in sugar content of nectar were observed. These changes, decreasing the osmotic potential of nectar, might allow a more consistent growth of epiphytic bacteria on blossoms. On leaves were found similar differences as well. As far as the interactions between E. amylovora and host plant, they were deeply investigated by advanced microscopical analysis. The influence of dioxygenase inhibitors and SAR inducers application on the infection process and migration of pathogen inside different plant tissues was studied. These microscopical techniques, combined with the use of gpf-labelled E. amylovora, allowed the development of a bioassay method for resistance inducers efficacy screening. The final part of the work demonstrated that the reduction of disease susceptibility observed in plants treated with prohexadione-calcium is mainly due to the accumulation of a novel phytoalexins: luteoforol. This 3-deoxyflavonoid was proven to have a strong antimicrobial activity.

Reconceptualising professional development in early childhood education. A study on teachers' professionalism carried out in Bologna province.

The research undertaken for this doctoral thesis explores the issue of teachers professionalism within pre-school institutions. The issue of early childhood professionalism has become increasingly important in the academic debate over the last decade as it is documented by a growing body of research published on the topic both nationally (Contini & Manini, 2007; Bondioli & Ferrari, 2004) and internationally (Peeters, 2008; Urban & Dalli, 2008; Urban, 2010). The study presented in this thesis aims at investigating teachers’ conceptualisations of professionalism by focusing on their understandings of educational work. The idea standing at the core of this research is that exploring the concept of professionalism from a ground-up perspective could lead to important reflections for a re-conceptualisation of professional development as a space for change directed from within institutions. The study is framed within a broadly sociological concern that inform the data analysis by contextualising the issue of early childhood professionalism in the contemporary socio-political arena. The research involves sixty teachers operating in state, municipal and private pre-school institutions located in Bologna province that took part to focus groups and interviews. The empirical materials, consisting of oral and written statements, are interpreted through phenomenographical analysis that gives account of how features of professionalism vary across the different institutional settings in which they are played out. This thesis, written in English and informed by an European research background, offers a contribution to the furthering of systemic approaches to the investigation of early childhood education professionalism in the context of the national and international academic debate.