ABSTRACT
Lasiodiplodia is a common pathogen causing dieback, gummosis, or root necrosis on the three most important fruit crops in Oman and the United Arab Emirates (UAE): date palm (Phoenix dactylifera), Citrus spp., and mango (Mangifera indica). A study was conducted to examine diversity in 64 Lasiodiplodia isolates infecting date palm (24), Citrus (11), and mango (29) in Oman and the UAE. Identification based on sequences of the internal transcribed spacer (ITS) rDNA and EF1α gene showed that date palm isolates belonged to L. hormozganensis (75% of isolates) and L. theobromae (25%); Citrus isolates belonged to L. hormozganensis (45%), L. theobromae (45%), and L. iraniensis (10%); and mango isolates belonged to L. theobromae (59%), L. iraniensis (34%), and L. hormozganensis (7%). Amplified fragment length polymorphism (AFLP) fingerprinting of the 64 isolates using four primer pair combinations produced 64 genotypes and 972 polymorphic alleles. Cluster analysis separated the isolates into four clusters representing the three species. A higher level of genetic diversity was observed in L. iraniensis (0.3105) compared to L. hormozganensis (0.2503) and L. theobromae (0.2331) in Oman. Analysis of molecular variance (AMOVA) indicated the existence of low levels of genetic differentiation among date palm populations of L. hormozganensis obtained from Oman and the UAE (FST = 0.025) and among populations of L. hormozganensis (0.0485) and L. theobromae (0.0703) from date palm, Citrus, and mango. These findings imply a high rate of movement of L. hormozganensis and L. theobromae isolates among date palm, Citrus, and mango and between the two countries. Findings from the pathogenicity test supported the AMOVA analysis and suggested a lack of host specialization in L. hormozganensis, L. iraniensis, and L. theobromae on date palm, acid lime, and mango. Although this is the first record of L. hormozganensis and L. iraniensis in Oman, the relatively moderate level of genetic diversity in the two species compared to L. theobromae suggests that the two species have been in Oman for a long time but misidentified by morphology and ITS rDNA sequences as L. theobromae. This study is also the first record of date palm and acid lime as natural hosts for L. hormozganensis and the first record of L. hormozganensis in the UAE. The diversity in Lasiodiplodia species affecting date palm, Citrus, and mango in Oman and the UAE should be taken into consideration when planning future management programs for diseases caused by these pathogens.
ABSTRACT
BACKGROUND: The role of two recently identified polyomaviruses, KI and WU, in the causation of respiratory disease has not been established. OBJECTIVES: To determine the prevalence of KI and WU viruses (KIV and WUV) in 371 respiratory samples and evaluate their contribution to respiratory disease. STUDY DESIGN: Specimens were screened for KIV and WUV using single, multiplex or real time PCR; co-infection with other respiratory viruses was evaluated. RESULTS: Of the 371 samples analysed, 10 (2.70%) were positive for KIV and 4 (1.08%) were positive for WUV yielding an overall case prevalence of KIV and WUV infection of 3.77%. KIV and WUV were identified in patients aged<15 years (11 patients) with upper or lower respiratory tract infection and >45 years (3 patients) with upper respiratory tract infection. Co-infections were found in 5 (50%) and 3 (75%) of the KIV and WUV positive samples, respectively. CONCLUSIONS: This study supports previous conclusions that KIV and WUV detection in the respiratory tract may be coincidental and reflect reactivation of latent or persistent infection with these viruses. The age distribution of KIV and WUV infection in this study mirrors that found for the other human polyomaviruses, BK and JC.
