Judith K Brown

Abstract:

Phylogenetic relationships for Bemisia tabaci were reconstructed by analysis of a -780 bp fragment of the mitochondrial cytochrome oxidase I (mtCOI) gene with an emphasis on geographic range and distribution among eight eudicot plant families that are common hosts of B. tabaci worldwide to elucidate key phylogeographic linkages between populations extant in China (n=31) and India (n=34). Bootstrap values for the Maximum Parsimony tree were highly robust for all major nodes involving the major Asian clade, subgroups, and sister groups within, at 92%-100%. Between-clade distances for the Southeast Asia and three other major clades, e.g. from sub-Sahara Africa, North Africa-Mediterranean, and the Americas, were approximately >16% divergent. Two major Asian subgroups (I, II) were resolved, which represented populations indigenous to the region, comprising two (Ia, Ib) and five (II a-e) sister groups, respectively, which diverged by 11%. Two distinct populations from sunflower in Hyderabad grouped separately within the two Asian subgroups. All other populations grouped uniquely within Asian subgroup II or I. The B biotype was identified in 23 collections from China at 97.3%-99.5% nucleotide identity with B biotype reference sequences; it was not identified in collections from India. The majority of haplotypes were associated with 3-4 plant families, with one exception that for sister group IId (sesame, India), it might be monophagous. Thus, B. tabaci from the southeastern and near eastern regions of the Asian continent comprise of a large number of ancestral, richly divergent, mostly polyphagous populations. This region is therefore hypothesized to constitute an important Old World center of diversification for the B. tabaci complex, together with sub-Saharan Africa.

Hadjistylli, M., SA.Schwartz, JK. Brown, and GK. Roderick. 2014. Isolation and characterization of nine microsatellite loci from the sweetpotato whitefly Bemisia tabaci biotype B. Insect Science (accepted).

Abstract:

The fine structure of the mouthparts of the whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), was examined by scanning and transmission electron microscopy. Adult whitefly mouthparts are similar to those of other homopterans, especially aphids, being composed of the labrum, the labium, and the stylets. The stylet bundle is the feeding organ of the whitefly and is composed of 2 mandibular stylets and 2 maxillary stylets. Mandibular stylets, which are located on the outer aspect of the stylet bundle, each contain 2 dendrites. The tips of the mandibular stylets are curved inward, and there are barb-like ridges on the lateral aspects, which probably function in piercing and cutting plant tissues and in anchoring the stylets in the tissues. The maxillary stylets are not innervated and are interlocked to form 2 separate compartments, the food canal and salivary canal. At the distal end of the interlocked maxillary stylets, there is a small depression, which may allow for mixing of the salivary canal and food canal components. Movement of the B. tabaci stylets during feeding is discussed in comparison with other homopterans. © 1995.

Varsani, A., Martin, D.P., Navas-Castillo, J., Moriones, E., Hernández-Zepeda, C., Idris, A.M., Murilo, F., Zerbini, F.M., and Brown, J.K. 2014. Revisiting the classification of curtoviruses based on genome-wide pairwise identity. Arch. Virol. 159: 1873-1882.

Abstract:

There are measurable differences between whitefly populations from different biogeographic backgrounds. These differences influence the capacity of B. tabaci (Hemiptera: Homoptera: Aleyrodidae) populations to vector WFT geminiviruses and are seen in whitefly host range phenotypes and host preferences that affect the ability and efficiency of whitefly mediated geminivirus transmission to and from certain hosts. Also suggestive of differences between populations are variable levels of fecundity, and that females do not mate with males from (putatively) genetically distinct populations.