Activity of essential oils and bacterial isolates to control bacterial strains causal agents of hazelnut decline in Sardinia In order to control the damage caused by Pseudomonas syringae pv. coryli (Psc), P. s. pv. syringae (Pss) and Xanthomonas arboricola pv. corylina (Xac), causal agents respectively of “twig dieback”, “twig and branch wilting” and “bacterial blight” of hazelnut in Sardinia, nine essential oils extracted from plants of Artemisia arborescens, Bupleurum fructicosum, Foeniculum vulgare, Lavandula stoechas, Mentha pulegium, Myrtus communis, Rosmarinus officinalis, Salvia desoleana and Thymus capitatus grown in Sardinia, and five bacterial antagonistic isolated from thymus plants (DPPSS T1, DPPSS T2, DPPSS T3, DPPSS T4 and DPPSS T5) were tested. Antagonistic isolates were positive for Gram reaction and endospore formation, negative for oxidase; Biolog system identified our isolates as Bacillus amyloliquefaciens. In a preliminary trial essential oils and antagonistic bacteria were screened in vitro by the diffusion agar method for antibacterial activity against four pathovars of Pss, two of Psc and two of Xac. In order to determine the minimum inhibitory concentration, the more efficacious ones (Fennel, Mint, Myrtle, Rosemary and Thyme) were tested in nutrient broth. For Fennel, Mint and Myrtle oils the minimum inhibitory concentration was 600 ppm, for Thyme was 400 ppm, while, for Rosemary oil, the minimum inhibithory concentration was above 800 ppm. Among the antagonistic bacteria, DPPSS T 2 and DPPSS T 3 were the most efficacious. Fennel, Mint, Myrtle and Thyme essential oils were tested for toxicity on hazelnut and tomato plants and lemon fruits. Fennel essential oil was more toxic than Mint on hazelnut leaves; while Thyme essential oil was toxic on tomato plants only. Antagonistic bacteria DPPSS T 2 and DPPSS T 3 were not able to elicit the hypersensitivity reaction on tobacco leaves and were not pathogenic on hazelnut and tomato plants and lemon fruits. The effectiveness of essential oils and antagonistic bacteria to control bacterial pathogens (Pss, Psc and Xac) were evaluated on hazelnut and tomato plants and for Pss strains also on lemon fruits experimentally infected. The results (observations and isolations on suitable media) showed that essential oils and antagonistic bacteria were able to prevent infections when plants and fruits were treated before inoculation.
Al fine di contenere i danni causati da Pseudomonas syringae pv. coryli (Psc), P. s. pv. syringae (Pss) e Xanthomonas arboricola pv. corylina (Xac), agenti rispettivamente della “moria dei rametti”, dell’“avvizzimento dei rametti e delle branche” e del “bacterial blight” su nocciolo in Sardegna, sono stati saggiati nove oli essenziali (Artemisia arborescens, Bupleurum fructicosum, Foeniculum vulgare, Lavandula stoechas, Mentha pulegium, Myrtus communis, Rosmarinus officinalis, Salvia desoleana e Thymus capitatus) estratti da piante coltivate in Sardegna e cinque ceppi antagonisti isolati da piante di timo (DPPSS T1, DPPSS T2, DPPSS T3, DPPSS T4 e DPPSS T5). Gli antagonisti erano Gram positivi, formavano endospore, negativi all’ossidasi e in base ai profili nutrizionali ottenuti con il sistema Biolog sono stati ascritti a Bacillus amyloliquefaciens. Preliminarmente in vitro è stata determinata, con il metodo della diffusione in agar, l’attività antibatterica di oli essenziali e antagonisti nei confronti di quattro ceppi di Pss, due di Psc e due di Xac. Per gli oli più efficaci (Finocchio, Menta, Mirto, Rosmarino e Timo), è stata determinata, in brodo nutritivo, la concentrazione minima inibitoria. Essa era di 600 ppm per gli oli di Finocchio, Menta e Mirto; di 400 ppm per l’olio di Timo; per il Rosmarino era superiore a 800 ppm. Fra i ceppi antagonisti, l’efficacia maggiore è stata mostrata dagli isolati DPPSS T2, DPPSS T3. I quattro oli essenziali più efficaci (Finocchio, Menta, Mirto e Timo) sono stati saggiati per la fitotossicità su piantine di nocciolo, pomodoro e frutti di limone. Su foglie di nocciolo sono risultati fitotossici l’olio essenziale di Finocchio ed in minor misura quello di Menta; quello di Timo è risultato fitotossico sulle piantine di pomodoro. Gli antagonisti DPPSS T2 e DPPSS T3 saggiati per la reazione di ipersensibilità su tabacco e la patogenicità su piantine di nocciolo, pomodoro e frutti di limone sono risultati negativi. La capacità di controllo di oli e antagonisti degli otto ceppi batterici (Pss, Psc e Xac) è stata valutata in infezioni sperimentali su piantine di nocciolo allevate in vaso e, per i ceppi di Pss, anche su frutti di limone. I risultati (osservazioni e isolamenti su mezzi idonei) hanno indicato che oli e antagonisti irrorati prima delle inoculazioni erano in grado di prevenire le infezioni.
Attività di prodotti eco-compatibili per il controllo di agenti del “deperimento” del nocciolo in Sardegna / Fiori, Mario; Falchi, G.. - 1:(2007), pp. 191-202. (Intervento presentato al convegno La Corilicoltura Biologica in Italia, Risultati di un triennio di studi del progetto CO.RI.BIO. Ricerche sul nocciolo finalizzate all'ottenimento di produzioni biologiche di qualità. tenutosi a Giffoni Valle Piana (SA) nel 13 dicembre 2007).
Attività di prodotti eco-compatibili per il controllo di agenti del “deperimento” del nocciolo in Sardegna.
FIORI, Mario;
2007-01-01
Abstract
Activity of essential oils and bacterial isolates to control bacterial strains causal agents of hazelnut decline in Sardinia In order to control the damage caused by Pseudomonas syringae pv. coryli (Psc), P. s. pv. syringae (Pss) and Xanthomonas arboricola pv. corylina (Xac), causal agents respectively of “twig dieback”, “twig and branch wilting” and “bacterial blight” of hazelnut in Sardinia, nine essential oils extracted from plants of Artemisia arborescens, Bupleurum fructicosum, Foeniculum vulgare, Lavandula stoechas, Mentha pulegium, Myrtus communis, Rosmarinus officinalis, Salvia desoleana and Thymus capitatus grown in Sardinia, and five bacterial antagonistic isolated from thymus plants (DPPSS T1, DPPSS T2, DPPSS T3, DPPSS T4 and DPPSS T5) were tested. Antagonistic isolates were positive for Gram reaction and endospore formation, negative for oxidase; Biolog system identified our isolates as Bacillus amyloliquefaciens. In a preliminary trial essential oils and antagonistic bacteria were screened in vitro by the diffusion agar method for antibacterial activity against four pathovars of Pss, two of Psc and two of Xac. In order to determine the minimum inhibitory concentration, the more efficacious ones (Fennel, Mint, Myrtle, Rosemary and Thyme) were tested in nutrient broth. For Fennel, Mint and Myrtle oils the minimum inhibitory concentration was 600 ppm, for Thyme was 400 ppm, while, for Rosemary oil, the minimum inhibithory concentration was above 800 ppm. Among the antagonistic bacteria, DPPSS T 2 and DPPSS T 3 were the most efficacious. Fennel, Mint, Myrtle and Thyme essential oils were tested for toxicity on hazelnut and tomato plants and lemon fruits. Fennel essential oil was more toxic than Mint on hazelnut leaves; while Thyme essential oil was toxic on tomato plants only. Antagonistic bacteria DPPSS T 2 and DPPSS T 3 were not able to elicit the hypersensitivity reaction on tobacco leaves and were not pathogenic on hazelnut and tomato plants and lemon fruits. The effectiveness of essential oils and antagonistic bacteria to control bacterial pathogens (Pss, Psc and Xac) were evaluated on hazelnut and tomato plants and for Pss strains also on lemon fruits experimentally infected. The results (observations and isolations on suitable media) showed that essential oils and antagonistic bacteria were able to prevent infections when plants and fruits were treated before inoculation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.