Species within the Bemisia tabaci (Hemiptera: Aleyrodidae) complex in soybean and bean crops in Argentina

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a cryptic species complex that contains some of the most damaging pests in tropical and subtropical regions. Recent studies suggested that this complex is composed of at least 24 distinct species. We use the approach from these studies to consider the identity of B. tabaci in Argentina. Previous studies have suggested the presence of a B. tabaci presumably indigenous to the Americas and referred to as the BR biotype in Argentina. We placed the entity referred to as the BR biotype within the B. tabaci cryptic species complex using whiteflies collected in soybean and bean crops in northern and central Argentina. The whiteflies were assigned using the mitochondrial cytochrome oxidase (mtCOI) gene. Four unknown haplotypes plus two Argentina sequences from GenBank formed a cluster that was basal to the rest of the New World sequences. These sequences diverged from the consensus sequence across the range of 3.6 to 4.3%. Applying the species assignment rules of recent studies suggests that the individuals from Argentina form a separate species. A fifth unknown haplotype fell within the New World putative species and formed a distinct cluster with haplotypes from Panama. These results suggest that Argentina has two indigenous species belonging to the B. tabaci cryptic species complex. Rather than using mtCOI sequencing for all B. tabaci collected, a simple random amplified polymorphic DNA-polymerase chain reaction diagnostic was used and tested along with previously published primers designed to work specifically with the BR biotype from Brazil. These primers were either unable to distinguish between the two indigenous members of the complex in Argentina or indicated a difference when none was evident on the basis of mtCOI sequence comparison.     

Dipsacus fullonum: an Alternative Host of Sunflower chlorotic mottle virus in Argentina

Dipsacus fullonum L. is a biennial weed that is widely spread in the Pampean region of Argentina. Plants of this species showing leaf mosaic symptoms were collected near sunflower ( Helianthus annuus L.) crops infected with Sunflower chlorotic mottle virus (SuCMoV). Symptomatic plants were tested by biological, serological and molecular assays. Sunflower and Nicotiana occidentalis L. plants mechanically inoculated with extracts from symptomatic D. fullonum leaves developed typical SuCMoV symptoms. Samples were DAS-ELISA positive when probed with a SuCMoV antiserum. RT-PCR was used to amplify the whole coat protein gene of the infecting virus. An 807 bp fragment was amplified, cloned and sequenced. The deduced amino acid sequence (EU606023) shared 96% amino acid identity with the SuCMoV sequence (AF255677). These results indicate that D. fullonum mosaic is caused by an isolate of SuCMoV. Thus, this finding has epidemiological relevance as the weed may act as a natural virus reservoir.