The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://http://dspace.unitus.it:80 2013-05-20T07:31:55Z 2013-05-20T07:31:55Z Aleandri, Maria Pia http://hdl.handle.net/2067/73 2011-01-25T10:07:41Z 2006-01-30T23:00:00Z

Title: Il processo infettivo di Fusarium Culmorum su plantule di frumento: degradazione delle componenti della parete cellulare, induzione di metaboliti di difesa e varaizione del ph tissutale Authors: Aleandri, Maria Pia Abstract: Fusarium culmorum rappresenta uno dei più pericolosi e diffusi agenti causali del "mal del piede del frumento". Un obiettivo di ricerca è quello di chiarire i meccanismi coinvolti nell'interazione fra tale patogeno e il frumento, in particolare verificare l'azione degli enzimi pectolitici fungini ed i mezzi di difesa attuati dall'ospite, può risultare di rilevante interesse anche per impostare innovative strategie di difesa. F. culmorum è in grado di produrre in vitro sia pectin liasi (PNL) che poligalatturonasi (PG). La PNL totale ha un grande potenziale degradativo sulla parete cellulare dell'ospite con prevalente attività catalitica su pectina ed a pH 8.5. Tale enzima è attivo anche su acido poligalatturonico ed in assenza di ioni Ca2+; dosi incrementali del catione aumentano in modo consistente l'attività catalitica. L'attività PNL e PG sono rappresentate da un complesso isoenzimatico. Nelle prime fasi di crescita il fungo produce in vitro esclusivamente PG, mentre nelle fasi successive viene prodotta in modo preponderante PNL accompagnata da un aumento del pH fino al valore coincidente con quello ottimale per l’attività pectinliasica. Il patogeno è in grado di produrre anche durante la colonizzazione di plantule di frumento un complesso isoenzimatico simile a quello osservato in vitro e di provocare un aumento del pH tissutale, anche se meno evidente di quanto saggiato in vitro. I risultati ottenuti indicano come F. culmorum sia in grado di modulare il pH nell'ambiente di crescita in funzione della dinamica dell'attività pectolitica verso valori congeniali alla attività pectinliasica.; Foot rot caused by Fusarium culmorum represents one of the most serious seed- and soil-borne diseases of wheat worldwide. During an ongoing research focused on the plant-microbe interaction wheat-F.culmorum, pectolytic enzymes produced by this pathogen in a liquid medium containing pectin as sole carbon source and in inoculated wheat seedlings were studied quantitatively and qualitatively. The pathogen was capable to produce in vitro both polygalacturonase (PG) and pectin-lyase (PNL). Total PNL was found to be active also on polygalacturonic acid and in the absence of Ca++; however, increasing doses of this cation consistently augmented the catalytic activity. Total PNL and PG activity was represented by an isoenzymatic complex. During early growing, F. culmorum produced in vitro only PG, whereas during further phases the pathogen produced mainly PNL accompanied by an increase of pH value of medium close to the PNL optimum activity. Moreover, PNL isoenzymes were differentially active at diverse pH values, thus indicating a high degree of flexibility of this enzyme complex. F. culmorum was capable to produce a pectolytic isoenzymatic pattern similar to that observed in vitro also during wheat seedlings colonisation and to enhance tissue pH level, even if less pronounced than that observed in vitro. Results suggest that alkalinisation process may represent a co-factor of F. culmorum pathogenicity. Description: Dottorato di ricerca in Protezione delle piante

2006-01-30T23:00:00Z Aleandri, Maria Pia Reda, Roberto Tagliavento, Vincenzo Magro, Paolo Chilosi, Gabriele http://hdl.handle.net/2067/1808 2011-04-12T09:27:25Z 2009-12-31T23:00:00Z

Title: Effect of Chemical Resistance Inducers on the Control of Monosporascus Root Rot and Vine Decline of Melon Authors: Aleandri, Maria Pia; Reda, Roberto; Tagliavento, Vincenzo; Magro, Paolo; Chilosi, Gabriele Abstract: The effect of the resistance inducers methyl jasmonate (MeJA), acybenzolar-S-methyl (BTH) and dipotassium hydrogenphosphate (K2HPO4) was tested by seed soaking and by foliar application to determine whether these resistance inducers controlled root rot and vine decline of melon caused by Monosporascus cannonballus. Tests were carried out in pots and under field conditions in a two-year trial. Application of MeJA to melon seed significantly reduced symptoms of melon root rot and vine decline in soil artificially inoculated with M. cannonballus, and seeds treated with BTH and K2HPO4 produced plants with a slightly greater resistance to the pathogen. Greenhouse experiments in soil naturally infected with M. cannonballus in 2006 showed that MeJA treatments by seed soaking followed by foliar applications decreased the severity of the disease. In 2007, both MeJA and BTH significantly reduced root rot and vine decline, but K2HPO4 was ineffective. The resistance inducers differentially induced the synthesis of a number of pathogenesis related (PR) protein isoenzymes, markers of induced resistance in the root system. Using MeJA to induce resistance to root rot and vine decline of melon caused by M. cannonballus may provide a practical supplement to an environmentallyfriendly disease management when it is combined with appropriate integrated agronomic practices.

2009-12-31T23:00:00Z