In this study, the dynamic population and distribution of several different isolates of Pseudomonas spp., which were genetically related, on various organs of tomato (roots, stems, crown, leavese and apex) were determined under conditions of relatively low as well as high humidity (greenhouse and growth chamber respectivily). Results showed that under conditions of high humidity bacterial colonization increased on all organs. Symptoms of bacterial speck of tomato were observed when tomato plantlets were transferred to high humidity conditions. The apex and crown showed higher levels of bacterial colonization. Multiplication rates in hrp isolates, in high humidity conditions, were significantly lower than in wild type isolates on all organs. Hrp mutant in low humidity conditions could only be identified on the crown. Dynamic population of saprophytic bacteria in greenhouse and growth chamber conditions was similar. Amongst saprophytic bacteria, most were identified as Stenotrophomonas maltophilia . It is concluded on the whole that, under conditions of high humidity, bacterial multiplication rates on all organs increased leading to bacterial speck of tomato in sensitive plant organs such as leaves and fruits.
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