A TRANSCRIPTOMIC APPROACH TO UNDERSTAND INDUCED RESISTANCE TO BACTERIAL CANKER OF STONE FRUITS ELICITED THROUGH TREATMENTS WITH COPPER GLUCOHUMATES.

Bacterial canker of stone fruits, caused by Xanthomonas arboricola pv. pruni, is a recurrent disease in Italian peach and plum orchards. Several field and glasshouse trials on peach and plum were done, with the aim to effectively control the disease by using some novel molecules, such as glucohumates. The most remarkable results were obtained with copper glucohumates (with a reduction of the disease by ca. 80%). Results are very promising and suggest the possibility to implement effective control strategies, where copper compounds and novel molecules are both used in commercial orchards. In order to study and understand the effect of the biomolecules used, untreated and glucohumate-treated peach plants were subject to further molecular analyses in order identify possible genes/sequences involved in the induction of disease resistance. A transcriptomic approach was developed for detecting the transcripts present in plant tissues, after elicitation of an induced protection state. Total RNA was extracted, retro-transcribed and c-DNA-AFLP was done to identify different sequence fingerprints in the protected plant tissue. Discrimination of newly expressed sequences was performed with DHPLC, and comparison of transcripts was done on the complete peach genome database in order to identify the genes or sequences involved in the elicitation of induced resistance. Preliminary data showed, in treated plants, the presence of nine putative genes like a putative senescence protein, already described as being involved in the induced resistance to fire blight in other Rosaceae. Thus, copper glucohumates might be considered possible candidates for the elicitation of resistance to bacterial diseases

AN INSIGHT IN SOME POPULATION FEATURES OF XANTHOMONAS ARBORICOLA pv. JUGLANDIS

Xanthomonas arboricola pv. juglandis (Xaj) is the causal agent of bacterial blight of walnut, an emerging disease, which has the potential to severely affect walnut orchards. An Italian strain collection of Xaj, obtained during the past 3 years from affected orchards in Romagna, was first assayed with conventional PCR with XajF/XajR primer pair developed to confirm strain identity. The population structure of the collection of Xaj isolates, confirms the presence of different genetic groups identified by rep-PCR (using Italian collection are currently being analysed by MLSA (multi locus sequence analysis), using 7 primers for 7 different housekeeping genes, with the purpose to better characterise the Italian isolates for phylotyping. The study of copper resistance on a wide collection of over 150 Xaj strains frequently showed high resistance (up to 500 ppm Cu++): two strains have been further studied confirming the presence of chromosomal genes copA and copB involved in the general copABCD copper resistance structure, as described for Pseudomonas syringae. Sequencing and comparing with other Xanthomonads were done. The elucidation of Xaj population structure may help to deeper investigate some additional aspects of the molecular epidemiology of the disease, thus allowing a better control strategy in the field. the REP, BOX and ERIC primers) and by multilocus sequence typing (MLST) and multilocus variable number analysis of tandem repeat (MLVA). Xaj and Xaj-like bacterial isolates from th

Shaping Mediterranean landscapes:The cultural impact of anthropogenic fires in Tyrrhenian southern Tuscany during the Iron and Middle Ages (800–450 BC / AD 650–1300)

Charcoal analysis, applied in sediment facies analysis of the Pecora river palaeochannel (Tyrrhenian southern Tuscany, Italy), detected the occurrence of past fire events in two different fluvial landforms at 800–450 BC and again at AD 650–1300. Taking place in a central Mediterranean district adequately studied through palaeoenvironmental and archaeological research, the investigation determined land changes, time phases and socio-economic driving forces involved in dynamic processes of fire. The fire sequences had purely anthropogenic origins and were linked to forest opening and reduction by local communities. Introduced by the Etruscans, fires dated to 800–450 BC involved mainly the forest cover on the hilly slopes, ensuring agricultural exploitation. From AD 650, fires contributed to Medieval upstream reclamation and vegetation clearing of flat swamplands. From AD 850 to 1050, the use of fire spread over a wider area in the river valley, increasing arable lands. Between AD 1150 and 1300, fires belonged to a regional forest clearance phase. Medieval fire episodes had a paramount importance in shaping and determining the character of the Tuscan Mediterranean landscape. From AD 850, Medieval fire clearing influenced regional vegetation history contributing to the decline of the dominant deciduous Quercus woodland. Open habitats became the new form of a clearly detectable agricultural landscape from AD 950. The use of fire clearing and the resulting landscape changes in the Pecora river valley depended on the political strategies adopted by Medieval authorities and marked, in fact, the progression of a cultural landscape still characterizing central Tyrrhenian Italy

Population features of Xanthomonas arboricola pv. pruni from Prunus spp. orchards in northern Italy

Bacterial leaf/fruit spot and canker of stone fruits, caused by Xanthomonas arboricola pv. pruni, is a recurrent disease in Italy. A set of 23 strains has been isolated in peach and plum orchards in an intensively stone fruit cultivated area located in north-eastern Italy. They were all identified as X. arboricola pv. pruni by means of phytopathological and serological features: hypersensitive reaction on bean pods, pathogenicity test on immature peach or plum fruitlets, identification by immunofluorescence assay and conventional PCR. Phylogenetic analysis based on sequencing of the gyrB housekeeping gene of the isolates showed that they formed a unique clade, well characterised and separated from other xanthomonads. An insight into the genetic population features was attempted by rep-PCR analysis, using the ERIC, REP and BOX primers. The combined rep-PCR fingerprints showed a slight intra-pathovar variation within our isolates, which grouped in five close clusters. Copper resistance has been assessed in vitro for our whole X. arboricola pv. pruni collection, highlighting that two isolates show a level of resistance in vitro up to 200 ppm of copper. Nonetheless, the copLAB gene cluster, present in many other species of Xanthomonads, was not detected in any isolate, confirming the presence of a still unknown mechanism of copper detoxification in our Xanthomonads arboricola pv. pruni tolerant/resistant strains

Genetic variations among Xanthomonas arboricola pv. pruni populations from peach orchards in Romagna

The genetic variability among populations of Xanthomonas arboricola pv. pruni, the causal agent of the bacterial canker of stone fruits, was studied. Results highlighted the uniformity of most bacterial populations isolated in different geographical areas and in different years. This implies the possibility to efficiently control the pathogen by using a suitable antagonist

Elicitation of resistance to bacterial canker of stone fruits by humic and fulvic acids (glucohumates): a cDNA-AFLP-dHPLC approach

Bacterial leaf/fruit spot and canker of stone fruits, caused by Xanthomonas arboricola pv. pruni is a challenging disease in Italian orchards. In recent years, novel molecules such as biostimulants or/and resistance-inducers have been developed and used to implement an effective Integrated Pest Management. An extensive study in vitro, in glasshouse and in a peach orchard was carried out to verify the efficacy of commercial glucohumates to control bacterial spot/canker outbreaks and to understand their mode of action. A transcriptomic approach was implemented to study the complex transcriptional changes that these biomolecules may possibly elicit in the plant-pathogen interaction. The cDNA-AFLP analysis of differential gene expression in treated plant tissue was made. Discrimination of differentially expressed sequences was made with denaturing High Performance Liquid Chromatography (dHPLC), and functional annotation of such transcripts was assigned based on similarity search on public genome databases. The results highlighted the activity of glucohumates in controlling Xanthomonas arboricola pv. pruni both in vitro and in vivo. Beneficial effects of humic substances towards this pathogen were confirmed by a significant disease reduction (up to 78%) in the commercial orchard. On the other hand, cDNA-AFLPdHPLC analysis allowed the collection of fourteen up-regulated transcript-derived fragments belonging to peach genes and putatively involved in the defence response. In particular, the activation of these genes within 24 h after treatment supposedly triggered the early-induced resistance, notoriously involved in maintaining a protection state in plants against biotic stresses

Use of a bacterial antagonist for the biological control of bacterial leaf/fruit spot of stone fruits.

The possibility of bio-controlling the bacterial canker of stone fruit is highlighted. The use of bacterial antagonists to control the pathogen Xanthomonas arboricola pv. pruni proved to be very efficient

Flora delle Balze di Verghereto, Monte Fumaiolo e Ripa della Moia

Viene presentata la flora vascolare di questo sito della Rete Natura 2000, esteso per circa 25 km2 nel sud-est dell’Emilia-Romagna, alla testa delle valli del Tevere, del Savio e del Marecchia. Il sito è stato da lungo tempo oggetto di numerosi studi botanici; l’elenco qui proposto è basato su flore e segnalazioni floristiche databili fra l’inizio del 1800 e i giorni nostri. Sono stati registrati 688 taxa specifici e sottospecifici, appartenenti a 99 famiglie. Si conferma la rilevante ricchezza biologica dell’area, seconda per importanza, a livello regionale, solo al Parco Nazionale delle Foreste Casentinesi