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Abstract

Pseudomonas syringae pv. syringae (Pss) constitutes a diverse group of bacterial strains that cause canker of stone fruits, blight of cereals and red streak of sugarcane. The purpose of this study was to determine how diverse Iranian strains of Pss are when they come from different hosts. We compared a total of 32 Pss strains isolated from stone fruits, barley, wheat and sugarcane from different geographical regions of Iran based on their phenotypic and molecular properties. Strains showed some variation regarding carbon and nitrogen utilization. Pss strains were similar in their protein banding patterns. Additional bands were found in sugarcane strains. Most strains showed one indigenous plasmid DNA and a few had two and some none. The genes of syrB and syrD encoding syringomycin synthesis and secretion, respectively, were amplified using specific primers in polymerase chain reaction. Syringomycin, producing strains amplified two DNA fragments of 752 and 446 bp representing syrB and syrD genes, respectively. Primer specificity was shown for Pss using various genera. Based on the results of this study, it is suggested that Pss strains from different hosts and geographical regions show diversity in phenotypic and molecular characters. It is thought that phenotypic variation is due to adaptation to specific hosts and niches for survival and pathogenicity.
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Abstract

Cucumber mosaic virus (CMV; family Bromoviridae, genus Cucumovirus) is the most cosmopolitan plant virus occurring worldwide. In the present study, leaf samples showing deformations, mosaics, and chlorotic spots symptoms were collected from naturally infected Basella alba, Telfairia occidentalis and Talinum fruticosum in a home yard garden in Ibadan, Nigeria. Total nucleic acid was extracted from leaves and used as template for cDNA synthesis. RT-PCR was carried out using CMV-specific primers targeting RNA-1 segment. Samples were also tested by RT-PCR using Potyvirus and Begomovirus genusspecific primers. DNA fragments with the expected sizes of ~500 bp were amplified by using CMV-specific primers; however, the expected amplicons were not produced using specific primers used for the detection of potyviruses and begomoviruses. The nucleotide and deduced amino acid sequences obtained for the isolates studied contained 503–511 nt and 144 aa, respectively. The isolates shared 81.9–85.3% nucleotide and 74.3–77.8% amino acid sequence identities with each other. The results of BLASTN analyses showed the highest identities of the isolates (80–93%) with CMV strains from Japan, USA and South Korea. Alignment of deduced partial protein revealed multiple amino acid substitutions within the three isolates and high identities with CMV subgroup I. Phylogenetic analyses putatively categorized the isolates in close association with subgroup IB isolates. The three isolates clustered together into a separate subclade, indicating possible new CMV strains. The results provide the first molecular evidence for CMV infections of T. fruticosum and B. alba in Nigeria and seem to show the possible presence of new strain(s). These findings also add three new hosts to the list of natural host range of the virus in Nigeria.
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