Judith K Brown

Abstract:

The molecular size limitations of the digestive system, including the filter chamber of immature and adult Bemisia tabaci (Gennadius) B biotype (= B. argentifolii), were studied by tracking the movement of fluorescent-labeled molecules and microspheres ingested by whiteflies. Soluble fluorescent molecules and labeled dextrans, ranging from 389 to 2,000,000 Da, were observed throughout the digestive tract of immatures 10-30 min after feeding was initiated. After removal of labeled molecules from the diet, fluorochromes were cleared from digestive system of immatures within 2 h. Fluorescent-labeled 0.1 - and 0.2-μm microspheres were ingested by larvae and saturated the digestive system within 2 h after initiation of feeding. Large, 0.5-μm spheres were not observed in the digestive tract of immatures, probably because singly or as aggregates, they were too large to enter the stylet food canal. The smallest spheres examined, 0.02 μm, were not detectable in the digestive tract of immatures. Observations for whitefly adults were identical to those for larvae, with two exceptions. In adults, soluble fluorochromes were detectable1 h after feeding commenced, and 0.02-μm spheres were observed primarily in the esophagus, filter chamber, anterior midgut, and hindgut, but not in the posterior portions of the midgut. We hypothesize that most of the 0.02-μm spheres ingested by adult whiteflies were shunted directly to the hindgut by way of the filter chamber, effectively bypassing the midgut. This is, therefore, a feasible route for virions of the plant pathogenic genus Begomovirus, which are of similar size to the small microspheres and are transmitted in a circulative manner by B. tabaci.

Hosseinzadeh, M.R., Shamsbakhsh, M., Kazempour Osalou, S., and Brown, J.K. 2014. Phylogenetic relationships, recombination analysis, and genetic variability among diverse variants of Tomato yellow leaf curl virus in Iran and the Arabian Peninsula: further support for a TYLCV-center of diversity. Arch. Virol.158: 485-497 DOI 10.1007/s00705-013-1851-z.

Abstract:

Collections of Jamaican whiteflies were identified using morphological characters. Those identified as Bemisia tabaci (Gennadius) were further identified to esterase type using diagnostic general esterase patterns using native polyacrylamide gel electrophoresis (PAGE). Over 216 B. tabaci adults from 22 Jamaican collections were identical to the B type esterase banding patterns identified first for the B biotype from Arizona, U.S.A. Of the plant species sampled in Jamaica, 86% were hosts of the B biotype of B. tabaci. Non-B esterase patterns were identified for two B. tabaci colonizing cassava and milkweed, respectively. Maximum likelihood and parsimony analyses of the mitochondrial (mt) 16S ribosomal ribonucleic acid (rRNA) sequences for Jamaican B. tabaci and reference sequences for well-studied B. tabaci haplotypes indicated that the non-B B. tabaci from Jamaica were of New World origin, whereas individuals identified as the B biotype were indistinguishable from those for other B biotype collections, worldwide. Bemisia tabaci collected from cassava in Jamaica was most closely related to the monophagous Jatropha biotype described in Puerto Rico, U.S.A., at 98.2% nucleotide identity. The collection from milkweed shared 98.4-99.6% nucleotide identity with several polyphagous haplotypes in the Americas and Caribbean region. The mt 16S rRNA sequence for the B biotype from tomato and muskmelon in Jamaica shared 99.1-99.3% nucleotide identity with the B biotype reference from Arizona. The presence of two New World haplotypes of B. tabaci in Jamaica are being reported for the first time, which may be analogous to the Jatropha and Sida biotypes (races), respectively, previously known only from Puerto Rico, and confirm that the exotic B biotype of B. tabaci is widespread in Jamaica.

Abstract:

The psyllids Diaphorina citri (Kuwayama) and Bactericera cockerelli (Sulc) (Hemiptera: Psyllidae) are vectors of Candidatus Liberibacter spp., bacterial agents of serious agricultural diseases. The rapidly expanding geographical distributions of these diseases dictate increasing urgency for their control. Therefore, it is important to gain a full understanding of the psyllid digestive system in which the vector-pathogen interactions begin. Their midgut is looped so that the foregut-midgut and midguthindgut transitional regions are grafted together to form a composite tube within a filter chamber sheath. Unwanted sap components could thus be extracted directly into the hindgut, bypassing digestion. The esophageal lumen enters the chamber axially to become the inner midgut lumen. The upper half of this midgut section is bulbous while the lower half is tubular. The tube lumen exits the chamber to become the external midgut lumen, which loops through the hemocoel and reenters the chamber, becoming the inner hindgut lumen. The inner hindgut tracks the adherent inner midgut in an antiparallel direction. The composite tube is helically wound and undergoes one hairpin turn. The inner hindgut straps diagonally across the bulb and then exits the chamber next to the esophagus as the outer hindgut to anus. The source of honeydew, whether filtrate, midgut waste, or both, is questioned. Paired, spherical, primary salivary glands each have a digitate accessory gland and a lateral duct that leads to the stylets. The accessory gland lumen is lined exclusively with intima, whereas the primary gland apical cell membranes are indicated to be more complex. © 2009 Entomological Society of America.