Judith K Brown

Idris, A.M., Al-Saleh, M.A.M., Amer, M., Abdalla, O., Al-Shahwan, I.M., and J.K.Brown. 2014. Introduction of Cotton leaf curl Gezira virus into the United Arab Emirates. Plant Dis. 98:1593.

Abstract:

The extent of genetic variability and host-plant distribution of Bemisia tabaci (Gennadius) genotypes colonising cultivated and uncultivated plant species occurring adjacent to cassava fields in selected cassava-producing areas of Uganda in 2003/04 were investigated using the mitochondrial cytochrome oxidase I (mtCOI) gene as the molecular marker. Eight genotype clusters, Ug1-Ug8, which are supported by high bootstrap values (≥80), at 3-18% nt divergence, were revealed among the collective Ugandan B. tabaci populations. Ug1 and Ug2 (both cassava-associated) and Ug8 (sweetpotato-associated) have been reported previously in Uganda. Ug3 was genetically dissimilar to B. tabaci described elsewhere and colonised a single species, Ocimum gratissimum. Ug4-Ug7 formed four closely related subclusters (93-97% nt identity) and diverged by 15-18% from Ug1, Ug2, Ug3 and Ug8, respectively. Ug4 had as its closest relatives (at 97-99% nt identity) the Ivory Coast okra biotype, whereas genotypes Ug5 and Ug6 had as their closest relatives (at 95-99% and 99% nt identity, respectively) the Mediterranean-North Africa-Middle East (MEDNAFR-ME) biotypes, which also include the well-studied B and Q biotypes. Ug7 was closely related (at 98-99% nt identity) to biotype Ms from the Reunion Island in the Indian Ocean. Ug4 colonised Cucurbita pepo, Cucurbita sativus, Leonotis nepetifolia and Pavonia urens, while Ug7 colonised Commelina benghalensis, Gossypium hirsutum and Phaseolus vulgaris. Ug6, the B-biotype-like genotype colonised Abelmoschus esculentus and C. benghalensis only. None of Ug4-Ug7 genotypes was found associated with, or colonising, cassava or sweetpotato plants. In addition to colonising sweetpotato, the Ug8 genotypes colonised Lycopersicon esculentum and L. nepetifolia. Ug6 and Ug7, both members of the B biotype/B-like cluster, induced silverleaf symptoms on Cucurbita sp. The discovery of five previously identified B. tabaci genotype clusters, Ug3-Ug7, in Uganda, among which are some of the world's most economically important biotypes, namely B and Q, is particularly significant in the spread of gemini-viruses with devastating effects to crop production in Africa. © 2005 The Authors.

PMID: 15660360;Abstract:

Salivary enzyme, glucose oxidase (GOX) from the caterpillar Helicoverpo zeo, catalyzes the conversion of glucose to gluconic acid and hydrogen peroxide. Because hydrogen peroxide has well-known antimicrobial properties, we examined whether caterpillar labial saliva could reduce the infectivity of bacterial pathogens. We examined the effects of caterpillar saliva on the growth of two bacteria species Serratia marcescens and Pseudomonas aeruginosa. Wells formed in LB agar contained a solution of salivary gland extract (Sx) and glucose, GOX and glucose, Sx only, GOX only, or glucose only. After 18 h of incubation, the diameter of cleared bacteria was measured. Wells treated with only GOX, Sx, or glucose showed no measurable area of clearing, while wells treated with GOX with glucose or Sx with glucose had considerable clearing. To determine if saliva could provide protection to caterpillars in vivo, a surgery was performed on caterpillars that prevented the secretion of labial saliva. Caterpillars were fed a diet containing either no added bacteria or treated with high levels of S. marcescens or P. aeruginosa. Caterpillars that could not secrete saliva had significantly higher levels of mortality when feeding on diet treated with either bacterium than caterpillars that could secrete saliva when feeding on equal levels of bacteria-treated diet. Our evidence demonstrates for the first time that insect saliva in situ can provide protection against bacterial pathogens and that the salivary enzyme GOX appears to provide the antimicrobial properties. © 2005 Wiley-Liss, Inc.

PMID: 22841489;Abstract:

The complete genome of 2780 bases was amplified using rolling circle amplification, and cloned, and sequenced for two distinct strains of the monopartite begomovirus Tomato leaf curl Sudan virus (ToLCSDV). The two strains shared 86-91% identity with the previously described ToLCSDV from the Nile Basin, and 90-91% identity with one another. One strain was cloned from symptomatic tomato plants from Tihamah (ToLCSDV-YE[YE:Tih:05]) while the other was cloned from symptomatic tobacco plants collected from Wadi Hadramaut (ToLCSDV-YE[YE:Had:89]). A distinct full-length betasatellite molecule (1352 bases) was cloned from the respective field-infected tomato and tobacco plants. Agro-inoculation of tomato and Nicotiana benthamiana plants with cloned partial tandem repeats of ToLCSDV-YE[YE:Tih11:05]) and the associated betasatellite, Tomato leaf curl Yemen betasatellite (ToLCYEB-[Tih:tom:137:05]), resulted in the reproduction of leaf curl disease symptoms in test plants like those observed in the field-infected plants. The betasatellite contributed to symptom severity in N. benthamiana test plants when it was co-inoculated with ToLCSDV-YE, compared to the milder symptoms that were observed in tobacco plants infected with the helper virus alone. © 2012 Elsevier B.V.