Resistance to Ralstonia Solanacearum of sexual hybrids between Solanum commersonii and S. tuberosum

This research was carried out to study the levels of bacterial wilt resistance and genetic diversity of (near) pentaploid sexual hybrids between S. commersonii (2n = 2x = 24, 1EBN) and cultivated S. tuberosum. Following artificial inoculations with Ralstonia solanacearum, wilting degree was estimated on a scale from 0 to 4, and seven genotypes of 26 (27%) displaying a S. commersonii like behavior were identified. Latent bacterial colonizations were detected in roots of symptomless S. commersonii and hybrids, whereas no bacterial populations were detected within stems. This suggests that the movement and/or growth of the bacterium in the aerial part were strongly inhibited. A molecular study with AFLP markers clustered hybrids into nine groups and provided evidence that resistant hybrids were slightly more similar to cultivated S. tuberosum than to the wild parent. This is important in view of the re-establishment of the cultivated genetic background through backcrosses. Hybrids displayed good fertility and are being used for further breeding efforts

Selection of a new Pseudomonas chlororaphis strain for the biological control of Fusarium oxysporum f. sp. radicis-lycopersici

Fluorescent pseudomonads possess several physiological characteristics exploitable for the biological control of phytopathogenic fungi. A group of 11 pseudomonads able to inhibit tomato pathogenic fungi in vitro were identified using the Biolog test and the phylogenetic analysis of recA. Strain M71 of Pseudomonas chlororaphis was selected as a new potential biocontrol agent. This strain drastically reduced Fusarium oxysporum f. sp. radicis-lycopersici pathogenicity on tomato plantlets in seed assays and greenhouse trials. Moreover, the strain produced several important secondary metabolites, including proteases, siderophores and antibiotics. The presence of a region involved in phenazine production and the biosynthesis of N-acyl homoserine lactones were also assessed

Resistance traits and AFLP characterization of diploid primitive tuber-bearing potatoes.

ISSN: 0925-986

Potential distribution of Xylella fastidiosa in Italy: a maximum entropy model

Species distribution models may provide realistic scenarios to explain the influence of bioclimatic variables in the context of emerging plant pathogens. Xylella fastidiosa is a xylem-limited Gram-negative bacterium causing severe diseases in many plant species. We developed a maximum entropy model for X. fastidiosa in Italy. Our objectives were to carry out a preliminary analysis of the species’ potential geographical distribution and determine which eco-geographical variables may favour its presence in other Italian regions besides Apulia. The analysis of single variable contribution showed that precipitation of the driest (40.3%) and wettest (30.4%) months were the main factors influencing model performance. Altitude, precipitation of warmest quarter, mean temperature of coldest quarter, and land cover provided a total contribution of 19.5%. Based on the model predictions, X. fastidiosa has a high probability (> 0.8) of colonizing areas characterized by: i) low altitude (0–150 m a.s.l.); ii) precipitations in the driest month < 10 mm, in the wettest month ranging between 80–110 mm and during the warmest quarter < 60 mm; iii) mean temperature of coldest quarter ≥ 8°C; iv) agricultural areas comprising intensive agriculture, complex cultivation patterns, olive groves, annual crops associated with permanent crops, orchards and vineyards; forest (essentially oak woodland); and Mediterranean shrubland. Species distribution models showed a high probability of X. fastidiosa occurrence in the regions of Apulia, Calabria, Basilicata, Sicily, Sardinia and coastal areas of Campania, Lazio and south Tuscany. Maxent models achieved excellent levels of predictive performance according to area under curve (AUC), true skill statistic (TSS) and minimum difference between training and testing AUC data (AUCdiff). Our study indicated that X. fastidiosa has the potential to overcome the current boundaries of distribution and affect areas of Italy outside Apulia

Fusarium oxysporum f.sp. radicis-lycopersici induces distinct transcriptome reprogramming in resistant and susceptible isogenic tomato lines

8openInternationalItalian coauthor/editorBackground: Fusarium oxysporum f.sp. radicis-lycopersici (FORL) is one of the most destructive necrotrophic pathogens affecting tomato crops, causing considerable field and greenhouse yield losses. Despite such major economic impact, little is known about the molecular mechanisms regulating Fusarium oxysporum f.sp. radicis-lycopersici resistance in tomato. Results: A transcriptomic experiment was carried out in order to investigate the main mechanisms of FORL response in resistant and susceptible isogenic tomato lines. Microarray analysis at 15 DPI (days post inoculum) revealed a distinct gene expression pattern between the two genotypes in the inoculated vs non-inoculated conditions. A model of plant response both for compatible and incompatible reactions was proposed. In particular, in the incompatible interaction an activation of defense genes related to secondary metabolite production and tryptophan metabolism was observed. Moreover, maintenance of the cell osmotic potential after the FORL challenging was mediated by a dehydrationinduced protein. As for the compatible interaction, activation of an oxidative burst mediated by peroxidases and a cytochrome monooxygenase induced cell degeneration and necrosis. Conclusions: Our work allowed comprehensive understanding of the molecular basis of the tomato-FORL interaction. The result obtained emphasizes a different transcriptional reaction between the resistant and the susceptible genotype to the FORL challenge. Our findings could lead to the improvement in disease control strategies.openManzo, D.; Ferriello, F.; Puopolo, G.; Zoina, A.; D’Esposito, D.; Tardella, L.; Ferrarini, A.; Ercolano, M.R.Manzo, D.; Ferriello, F.; Puopolo, G.; Zoina, A.; D’Esposito, D.; Tardella, L.; Ferrarini, A.; Ercolano, M.R

Trasferimento orizzontale del gene nptII da piante transgeniche a batteri fitopatogeni

Molti studi hanno dimostrato che con l’introduzione di piante geneticamente modificate possono verificarsi eventi inattesi a carico dei batteri “plant and soil associated”. Il DNA vegetale, rilasciato durante la degradazione dei tessuti, può persistere e rimanere biologicamente attivo anche per anni suggerendo che nella fitosfera i batteri presenti potrebbero venire a contatto con il DNA di piante GM e acquisire DNA esogeno. In questo studio è stata valutata la possibilità di trasferimento orizzontale del gene nptII, codificante per la neomicina fosfotransferasi II che determina la resistenza all’antibiotico kanamicina, da piante transgeniche a tre importanti specie batteriche patogene per il pomodoro: Pseudomonas syringae pv tomato, Pseudomonas corrugata e Ralstonia solanacearum. I batteri fitopatogeni sono stati modificati geneticamente in modo da contenere un gene della resistenza alla kanamicina non funzionante nptII omologo al gene nptII funzionante presente in linee di pomodoro transgeniche (var. Better Boy). nptII è stato ottenuto digerendo con due diversi enzimi di restrizione (NcoI e Thtt11) il gene nptII, in modo da introdurre una delezione di 317 bp nella parte centrale del gene stesso. I ceppi batterici ricombinanti sono stati sottoposti a esperimenti di trasformazione con DNA e omogenato di pomodoro geneticamente modificato allo scopo di valutare la capacità dei batteri di catturare ed integrare nel proprio genoma il gene nptII mediante ricombinazione omologa. L’integrazione di DNA transgenico di pianta nei batteri determina la riparazione del gene nptII e di conseguenza l’acquisizione della resistenza alla Kanamicina.. Dalle prove di trasformazione, eseguite in condizioni ottimizzate di laboratorio, non sono stati ottenuti trasformanti di R. solanacearum kanamicina resistente e sono stati ottenuti pochissimi trasformanti di P. syringae pv. tomato. P. corrugata è la specie che ha mostrato una frequenza di trasformazione maggiore, è stata quindi scelta questa specie per effettuare una serie di esperimenti al fine di valutare la possibilità di trasferimento genico orizzontale in diverse condizioni sia in vitro che in vivo. Negli esperimenti di trasformazione in vitro P. corrugata è risultata trasformabile da DNA plasmidico, da Dna estratto dalle piante transgeniche e da lisati cellulari batterici contenenti il gene nptII. Nelle prove in vivo, eseguite inoculando il ceppo patogeno direttamente nelle piante transgeniche, nessun ceppo di P. corrugata ricombiante kanamicina resistente è stato isolato dalle piante infettate neanche dopo 5 mesi dall’inoculo. Dai dati di questo lavoro si evince che P. corrugata è una specie sicuramente in grado di mettere in atto meccanismi per catturare ed integrare nel proprio genoma DNA esogeno di varia natura, ma nelle condizioni in vivo che sono state testate non si sono venute a creare le condizioni affinché i batteri potessero sviluppare la necessaria competenza per la trasformazione naturale