SLEEPING HIBISCUS A NEW HOST FOR PSEUDOMONAS VIRIDIFLAVA
K. Rouhrazi, H. Rahimian
Since 2008, a disease consisting of brown to black angular to irregular spots, 2-4 mm in diameter and surrounded by a chlorot- ic halo, was observed in northern Iran on the leaves of sleeping hibiscus (Malvaviscus penduliflorus), a widely cultivated orna- mental shrub. Bacterial colonies were isolated from symptomatic leaves on nutrient agar containing 5% sucrose. Twenty represen- tative isolates were Gram-negative and negative for oxidase and arginine dehydrolase, positive for fluorescent pigment produc- tion, potato soft rot, induction of a hypersensitive response on to- bacco, acid production from xylose and mannose, and utilization of D-tartrate. The isolates reacted negatively in tests for urease and nitrate reduction, acid production from cellobiose and rham- nose and utilization of L-tartrate (Lelliott and Stead, 1988). Path- ogenicity was ascertained by spraying a bacterial suspension cali- brated at 107 CFU/ml on two young sleeping hibiscus plants, which reproduced the field syndrome A 16S ribosomal RNA fragment of 1550 bp was amplified from 10 bacterial isolates by PCR using the primer A1/B6 (Manceau and Horvais, 1997). A partial 16S rRNA gene sequence was deposited in GenBank data- base under the accession No. JF836019. Homology searches with the 16S rRNA sequence in database showed that the isolates un- der study were most similar (100%) to pathogenic Pseudomonas viridiflava isolates ICMP 2848, LMG 2352. Based on phenotypic, pathogenicity and genomic properties, the bacterium that causes leaf spot of sleeping hibiscus was therefore identified as Ps. viridi- flava. To the best of our knowledge, this is first report of the oc- currence of Ps. viridiflava on sleeping hibiscus and the first record of its presence in Iran.