Abstract

The susceptibility of 93 different tomato cultivars that are commonly grown in greenhouses and field in the western Mediterranean region of Turkey have been assessed for resistance to bacterial speck disease caused by Pseudomonas syringae pv. tomato strains. The disease severity indexes (DSI) varied between zero and four for the tomato cultivars. Seven tomato cultivars showed hypersensitive reactions against strains of P. syringae pv. tomato carrying the avrpto1 gene. Six of these seven tomato cultivars had the PTO gene coding for resistance against bacterial speck. The PTO sequences from the tomato cultivars Atalay, Party, Petrus, Piccadilly, Prenses and Tyty had similarity of 94, 93, 94, 92, 95 and 94%, respectively, with the PTO sequence of Lycopersicon esculentum VFNT Cherry (AF220603), and had similarity of 98, 98, 96, 95, 100 and 98%, respectively, with the PTO sequence ofLycopersicon pimpinellifolium Rio Grande 76R (AF220602). These findings indicate a considerable variation in bacterial speck resistance and will aid in the choice of parental lines for breeding new tomato cultivars with resistance to bacterial speck.

Key words: avrpto, Mediterranean region, polymerase chain reaction, PTO.