Genetic diversity and infectivity analysis of tomato yellow leaf curl virus Oman and its associated betasatellite

Tomato yellow leaf curl virus-Oman (TYLCV-OM),  a variant of the Tomato yellow leaf curl virus-Iran (TYLCV-IR) strain, was identified in 2005 as the cause of tomato yellow leaf curl disease (TYLCD) in Oman and is  associated with a betasatellite namely as Tomato leaf curl betasatellite (ToLCB). Surveys were carried out from three diverse Governorates of Oman to investigate the correlation between the betasatellite and the virus. The visual assessment and scoring of infected tomato plants in the field revealed that the association of betasatellite with the disease was highest in Sharqia at 77%, followed by Dakhlia at41% and lowest in Batinah at30% . Ten isolates from three distinct regions of Oman were analyzed: two from Al Batinah, two from A'Dakhliah, and six from A'Sharquiah. All TYLCV-OM isolates were identified as variants of the 2005 isolates Al Batinah. However, a new recombinant form of TYLCV-OM, which could impact its virulence or spread, was identified in the Al Batinah region. Mutations observed in the Al Batinah isolates of TYLCV-OM coincided with recombination events involving ToLCOMV. Examination of the intergenic regions (IRs) of TYLCV-OM and ToLCOMV indicated that recombination occurred within the IR. Specifically, TYLCV-OM acquired a segment spanning coordinates 1 to 132 nt from ToLCOMV, which may influence its genetic diversity. The implications of these findings for the evolutionary dynamics of the begomovirus complex associated with yellow leaf curl disease are discussed. Inoculation of infectious construct of TYLCV-OM alone or with ToLCB resulted in severe leaf curl symptoms but leaf yellowing was more pronounced in the presence of ToLCB. Real-time quantitative data showed that TYLCV-OM was accumulated to higher level in the presence of betasatellite.