Large-scale cultivation of Pto-bearing tomato genotypes, resistant to bacterial speck disease caused by the race 0 of Pseudomonas syringae pv. tomato (Pst), is increasing the risk of Pst race 1 appearance, which overcomes this gene-for-gene resistance. The occurrence of race 1 in field was reported in Canada, Bulgaria, USA and Italy. In Italy, it was recorded in 1996, when Pto-tomato plants were rarely cultivated, albeit it did not cause significant damage. In 2008, a severe outbreak of bacterial speck disease was observed on Pto-bearing tomato plants in Cremona Province (northern Italy), from which we obtained 3 bacterial isolates. LOPAT tests, rep-PCR, PCR amplification of hrpZPst and pathogenicity tests on susceptible Rio Grande and resistant Ontario 7710 tomato plants confirmed that they belong to race 1 of Pst. By using PCR and suitable primer we further characterize these isolates as well as 5 race 1 and 9 race 0 Pst strains collected in Italy and California for the presence of the avrPto effector gene, whose product was found to interact with the Pto protein. All race 1 strains were lacking avrPto gene, while all race 0 strain contain it, except for 2 strain. We can therefore suppose a complete deletion of avrPto gene in race 1 strains. Since also avrPtoB was found to interact with Pto, further investigations are in progress to determine the presence of the avrPtoB gene in all strains studied.
Molecular characterization of Pseudomonas syringae pv. tomato strains overcoming the resistance of Pto-bearing tomato plants
MORETTI, Chiaraluce;BUONAURIO, Roberto
2009
Abstract
Large-scale cultivation of Pto-bearing tomato genotypes, resistant to bacterial speck disease caused by the race 0 of Pseudomonas syringae pv. tomato (Pst), is increasing the risk of Pst race 1 appearance, which overcomes this gene-for-gene resistance. The occurrence of race 1 in field was reported in Canada, Bulgaria, USA and Italy. In Italy, it was recorded in 1996, when Pto-tomato plants were rarely cultivated, albeit it did not cause significant damage. In 2008, a severe outbreak of bacterial speck disease was observed on Pto-bearing tomato plants in Cremona Province (northern Italy), from which we obtained 3 bacterial isolates. LOPAT tests, rep-PCR, PCR amplification of hrpZPst and pathogenicity tests on susceptible Rio Grande and resistant Ontario 7710 tomato plants confirmed that they belong to race 1 of Pst. By using PCR and suitable primer we further characterize these isolates as well as 5 race 1 and 9 race 0 Pst strains collected in Italy and California for the presence of the avrPto effector gene, whose product was found to interact with the Pto protein. All race 1 strains were lacking avrPto gene, while all race 0 strain contain it, except for 2 strain. We can therefore suppose a complete deletion of avrPto gene in race 1 strains. Since also avrPtoB was found to interact with Pto, further investigations are in progress to determine the presence of the avrPtoB gene in all strains studied.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
