RESUMO
BACKGROUND: The begomovirus, squash leaf curl virus (SLCuV) is one of the causal agents of squash leaf curl (SLC) disease, which is among the most destructive diseases of cucurbit crops in tropical, subtropical, and semiarid regions worldwide. This disease was originally reported in the American continent with subsequent spread to the Mediterranean basin. Up to now, SLCuV has only been detected by PCR in Mexico. This study provides the first complete sequence of a Mexican SLCuV isolate from Baja California Sur (BCS). In addition, the genome of the virus was characterized, establishing its phylogenetic relationship with other SLCuV isolates. METHODS: The full genome (DNA-A and DNA-B) was amplified by rolling circle amplification, cloned and sequenced and the open reading frames (ORF) were annotated. Virus identification was performed according to the International Committee on Taxonomy of Viruses (ICTV) criteria for begomovirus species demarcation. To infer evolutionary relationship with other SLCuV isolates, phylogenetic and recombination analyses were performed. RESULTS: The SLCuV-[MX-BCS-La Paz-16] genome (DNA-A and DNA-B) had 99% identity with SLCuV reference genomes. The phylogenetic analysis showed that SLCuV-[MX-BCS-La Paz-16] is closely related to SLCuV isolates from the Middle East (Egypt, Israel, Palestine and Lebanon). No evidence of interspecific recombination was determined and iterons were 100% identical in all isolates in the SLCuV clade. CONCLUSIONS: SLCuV-[MX-BCS-La Paz-16] showed low genetic variability in its genome, which could be due to a local adaptation process (isolate environment), suggesting that SLCuV isolates from the Middle East could have derived from the southwestern United States of America (USA) and northwestern Mexico.
RESUMO
For more than four decades, the presence of the whitefly Bemisia tabaci Gennadius complex as a pest and transmitter of begomoviral diseases has been one of the most important phytopathological events in cultivated species worldwide. In addition, the number of whitefly species, as well as the viruses they transmit, has been increasing over time. In the state of Baja California Sur (BCS), Mexico, the diversity of B. tabaci has been delimited to MEAM1 and NW species, affecting mainly tomato, pepper, and squash. However, the relationship of these species with the dispersion of the begomoviruses previously detected in the study area is still unknown. In a 5-yr study (2012-2016), these species of whiteflies and begomoviruses were identified. Moreover, the recurrence, seasonal distribution, and impact they have on the spread of the begomoviral diseases were assessed. The identification of whiteflies was done targeting the mtCOI by PCR-DNA barcoding assay. For begomoviruses identification, a set of degenerate and specific primers targeting the IR region and CP gene were used. To determine seasonal abundance, monitoring was performed every 15 d by means of yellow traps. The MEAM1 species in all localities was observed with the highest peak population (>10 whiteflies/trap) from March to April. The guidelines for naming begomovirus species for the International Committee on Taxonomy of Viruses (ICTV) establish that the names when they are preceded by the acronym the whole name is in lowercase, not italicized (e.g. bean golden mosaic virus (BGMV)); when the name goes alone without the acronym then its capitalizes the first letter (e.g. Bean golden mosaic virus) and when these are referred to in a taxonomic sense they are italicized and the first letter is capitalized (e.g. Bean golden mosaic virus). This study provides details of the distribution and occurrence of MEAM1 species and diversity of begomoviruses that could be useful in disease management in BCS and worldwide.