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Background The bacterial speck disease of tomato caused by a bacterial pathogen Pseudomonas syringae pv. tomato is a most important disease causing severe crop losses. Methods and results Present study was conducted to investigate and characterize the population diversity of P. syringae pv. tomato pathogen isolated from infected tomato plants from various regions of Egypt. Significant variation among the isolates was observed which demonstrated considerable virulence. All isolates were pathogenic and the CFU population recovered from inoculate tomato leaves by isolate Pst-2 was higher than other isolates. Genetic disparity among the isolates was investigated by PCR analysis by amplifying hrpZ gene using random amplified polymorphic DNA (RAPD), sequence-related amplified polymorphism (SRAP), and inter-simple sequence repeats (ISSR) markers. The amplified products for ITS1 were found to have 810 bp length whereas 536 bp length was observed for hrpZ gene using primer pairs (1406-f/23S-r) and (MM5-F, MM5-R) respectively. The restriction analysis of amplified regions “ITS” and hrpZ by using 5 and 4 endonucleases respectively demonstrated slight variation among the bacterial isolates. The results of RAPD, ISSR and SRAP showed higher polymorphism (60.52%) within the isolates which may assist for successful characterization by unique and specific markers based on geographical distribution, origin and virulence intensity. Conclusion The results of present study suggested that the use of molecular approach may provide successful and valuable information to differentiate and classify P. syringae pv. tomato strains in future for the detection and confirmation of pathogenicity.

The bacterial pathogen Pseudomonas syringae pv. tomato is the most important pathogen causing bacterial speck disease of tomato. Present study was conducted to investigate and characterize the population diversity of Pseudomonas syringae pv. tomato pathogen collected from infected tomato growing regions of Egypt. Significant variation was observed among the five isolates which showed significant level of virulence. Genetic variation among the isolates was investigated by PCR approach for the amplification of hrpZ gene using random amplified polymorphic DNA (RLFP), sequence-related amplified polymorphism (SRAP), and inters simple sequence repeats (ISSR). The length of amplified product for ITS1 region was 810 bp whereas for hrpZ gene was 536bp with primer pairs (1406-f/23S-r) and (MM5-F, MM5-R) respectively. The restriction analysis of amplified regions “ITS” and hrpZ by using 5 and 4 endonucleases respectively, showed slight variation among the bacterial isolates. The results of RAPD, ISSR and SRAP showed higher polymorphism (60.52%) between the isolates which assist for their successful characterization by unique and specific positive markers, based on geographical distribution, origin and virulence intensity. The results of this study suggested that the use of molecular approach can provide successful and valuable information for differentiation and classification of Pseudomonas syringae pv. tomato in future.

In this study; an isolate of Monilinia fructigena the causal agent of apple fruit brown rot was isolated from rotten apple fruits cv. Golden delicious. In the in vivo pathogenicity assay, it presented significant disease incidence on the inoculated apple fruit, thus confirming its virulence. Five endophytic yeasts were isolated from healthy apple fruits; identified according to their microscopic characteristics as; Schwanniomyces vanrijiae, Galactomyces geotrichum, Pichia kudriavzevii, Debaryomyces hansenii, and Rhodotorula glutinis. The first three isolates showed appreciable inhibitory potential against M. fructigena by in vitro test; moreover, they caused a significant inhibition of germination of pathogen conidia by 67.6–89.2%. Identification of these three potent yeasts in addition to M. fructigena isolate was confirmed by PCR analysis through amplification of ITS region. In in vivo assays, fruits were inoculated with each of the 5 BCAs and M. fructigena simultaneously; 24 h before, and 24 h after pathogen inoculation, showing a noticeable reduction of disease incidence by 84.02–89.5%, 80.1–86.9%, 56.3–86.9% respectively, compared with the controls. By in vitro plate assays, BCAs were able to produce fungal cell wall hydrolyzing enzymes such as: chitinases, pectinases, β-1,3-glucanase, and protease, in addition to the production of a killer toxin. At 10 mg/L of Fe+3 in PDA, the three BCAs recorded significant in vitro inhibition of M. fructigena growth. The three potent BCAs do not express human pathogenicity traits. The aims of the current study were to isolate and characterize yeasts able to inhibit the growth of M. fructigena during apple storage.