Uitenhage, South Africa
Uitenhage, South Africa

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McBride C.S.,Rockefeller University | McBride C.S.,Howard Hughes Medical Institute | McBride C.S.,Princeton University | Baier F.,Rockefeller University | And 10 more authors.
Nature | Year: 2014

Female mosquitoes are major vectors of human disease and the most dangerous are those that preferentially bite humans. A 'domestic' form of the mosquito Aedes aegypti has evolved to specialize in biting humans and is the main worldwide vector of dengue, yellow fever, and chikungunya viruses. The domestic form coexists with an ancestral, 'forest' form that prefers to bite non-human animals and is found along the coast of Kenya. We collected the two forms, established laboratory colonies, and document striking divergence in preference for human versus non-human animal odour. We further show that the evolution of preference for human odour in domestic mosquitoes is tightly linked to increases in the expression and ligand-sensitivity of the odorant receptor AaegOr4, which we found recognizes a compound present at high levels in human odour. Our results provide a rare example of a gene contributing to behavioural evolution and provide insight into how disease-vectoring mosquitoes came to specialize on humans. © 2014 Macmillan Publishers Limited. All rights reserved.

This catalogue provides a comprehensive record of the 284 entities of organisms (insect, mite and pathogen species, or biotypes thereof) that have featured in biological control of invasive alien plants (weeds) in South Africa, since 1913. Fourteen of these entities are native species, or foreign species that have, by some unknown means, entered the country, while the remainder were intentionally imported specifically for biological control. The majority (237 of 284, i.e. 83 %) are phytophagous insects, the balance being made up of five species of mites (Acari) and 42 entities of plant-pathogens. The catalogue comprises the names of each of the target weeds, their origin, and an assessment of the degree of control that has been achieved with biological control, together with names and details (feeding guild, date released where applicable, current status and extent of damage inflicted) for each of the agents. Key references are provided. Of the 270 entities that were introduced into quarantine and tested for host specificity: 106 (39 %) were eventually released as biological control agents; 16 % are still under investigation; approximately 24 % were rejected by researchers because of doubts about their safety or efficacy; and 21 % have been shelved pending possible further study. Two of the pathogen species were developed as mycoherbicides. Seventy-five (71 %) of the 106 agents that were released in South Africa have become established on 48 invasive alien plant species, in 14 plant families. According to a rating system that has been widely adopted since 1999, and slightly amended in this account, approximately 21 % of the weed species on which biological control agents are established have been completely controlled, and another 38 % are under a substantial degree of control.

In South Africa, two imported insect species have been used in attempts to control invasive Australian myrtle trees, Leptospermum laevigatum (Gaertn.) F.Muell. (Myrtaceae): a bud-galling midge, Dasineura strobila Dorchin (Diptera: Cecidomyiidae), which was inadvertently introduced, possibly in the mid-1980s, and a leaf-mining moth, Aristaea (Parectopa) thalassias (Meyrick) (Lepidoptera: Gracillariidae), which was released in 1996. The latter agent attacks young leaves only and has no discernible impact on mature trees. The number of L. laevigatum buds on mature trees that are galled by D. strobila was monitored from 1994 until 2008. Initially the prognosis for biological control by D. strobila was extremely promising. However, the numbers of galls then declined sharply at most of the sites, on average to less than half of their previous peak levels. Gall-midge mortality, induced by native parasitoids, was very low initially, and, some years later, peaked at an average of only about 8 %. In 2004, predatory mites, mostly Pyemotes species (Trombidiformes: Pyemotidae), were discovered, killing an average of 27% (9.8-61.3%) of the D. strobila larvae and pupae in the galls, but their role in regulating populations of D. strobila has not been proven. A chemical exclusion experiment on seedlings showed that leaf damage by A. thalassias together with galling by D. strobila reduced the growth of young L. laevigatum plants by nearly 50%, but, again, the impact of the two agents in aggregate, on mature plants, is negligible. A gall-inducing scale insect is presently under consideration as a potential agent, and there are some other possible agents that might be useful, but, overall, the prospects for biological control of L. laevigatum do not appear to be good.

In 2008, a field survey was conducted in northern Argentina to collect natural enemies of Cestrum species (Solanaceae) for use as biological control agents in South Africa. The rust fungus Uromyces cestri Bertero ex Mont. (Pucciniales: Pucciniaceae) was found on Cestrum parqui L'Hr. and imported into quarantine facilities in South Africa. No damaging pathogens were found on Cestrum laevigatum Schltdl. Preliminary host-range studies showed that U. cestri was able to infect and cause disease on C. parqui and on Cestrum elegans (Brongn. ex Neumann) Schltdl. in South Africa, and could have potential for the biological control of these species. The rust did not infect any of the other Cestrum species tested, and neither did it infect C. laevigatum which is the most problematic Cestrum species in South Africa.

Van Der Westhuizen L.,Plant Protection Research Institute
African Entomology | Year: 2011

Madeira vine, Anredera cordifolia (Ten.) Steenis subsp. cordifolia (Basellaceae), is native to South America but has become invasive and problematic in many countries, including South Africa. Weedy vines are notoriously difficult to control through conventional mechanical and chemical means, so biological control of A. cordifolia in South Africa was initiated in 2003. No agents have yet been released against this plant in South Africa but exploratory observations on the life-history and host-specificity of two leaf-feeding beetles, Phenrica sp. (Coleoptera: Chrysomelidae) from Brazil and Plectonycha correntina Lacordaire (Coleoptera: Chrysomelidae: Chrysomelinae) from Argentina and Brazil, are reviewed here. Adults and larvae of both chrysomelids feed extensively on leaves and new growth of A. cordifolia, resulting in leaf and above-ground biomass reductions. The laboratory host-ranges of these potential agents seem acceptably narrow, with normal development restricted to the host plant. Adult feeding was recorded on other non-indigenous species within the Basellaceae, Portulacaceae and Talinaceae. The Phenrica sp. colony, being reared in quarantine, died out and re-collection has not been possible. Host-specificity studies are continuing on P. correntina.

Goszczynski D.E.,Plant Protection Research Institute
Archives of Virology | Year: 2010

The presence of rugose-wood-associated viruses of the genera Foveavirus and Vitivirus in the family Betaflexiviridae was investigated in various clones of own-rooted and grafted Vitis vinifera cv. Shiraz that were affected, or not, by Shiraz decline, and in rootstocks. RT nested-PCR amplification of double-stranded RNA using degenerate primers for the simultaneous detection of foveaviruses and vitiviruses (Dovas CI, Katis NI in J Virol Meth 170:99-106, 2003), cloning of DNA amplicons, SSCP analysis of clones, sequencing and computer-assisted analysis of sequences was used to characterize viral genetic variability. A total of 1,137 clones were analysed by SSCP, and, of those, 371 clones were sequenced. The results revealed that variants of five molecular groups belonging to the species Grapevine rupestris stem pitting-associated virus (GRSPaV), including highly divergent variants related to strain SY (Lima MF et al. in Arch Virol 151:1889-1894, 2006) were present in plants of various clones of Shiraz regardless of their Shiraz decline status, and in rootstocks. Grapevine virus A (GVA) and grapevine virus B (GVB) were detected in a relatively small number of plants. This study suggested no involvement of GRSPaV, GVA or GVB in Shiraz decline. © 2010 Springer-Verlag.

Analysis of two Grapevine virus B (GVB)-infected LN33 hybrid grapevines revealed that a plant exhibiting clear symptoms of corky bark (CB) disease was infected with two molecular variants of the virus, whereas a plant exhibiting no disease symptoms was infected with only one variant. Sequence results indicated that the single variant in the CB-negative grapevine was also one of the two present in the CB-affected hybrid. Plant extracts from these two grapevines were used to successfully transmit the virus to N. benthamiana. After further cloning and sequencing, two clearly divergent variants were identified. Comparative molecular analysis of the variants, named here GVB 953-1 and GVB-H1, respectively, transmitted from CB-affected and consistently CB-negative plants, revealed short genomic regions, most of them highly divergent, that encoded amino acid sequences, containing significant amino acid substitutions altering the net charges of their respective proteins. Interestingly, a comparison of these variants to genome sequence data of GVB variants GVB Italy and GVB 94/971 available from the GenBank, revealed that these significant amino acid substitutions were the same for, and unique to, the variant pairs GVB 953-1/GVB Italy and GVB-H1/GVB 94/971. This despite the variants of each pair being otherwise clearly different at nucleotide and amino acid levels. In addition, both sets of variants differed substantially in their respective 3'-non-translated (3'NTR) regions. The relevance of these findings is discussed. © 2010 Springer Science+Business Media, LLC.

Goszczynski D.E.,Plant Protection Research Institute
Journal of Phytopathology | Year: 2013

The alignment of the complete genomes of genetic variants of Grapevine leafroll-associated virus 3 (GLRaV-3) representing phylogenetic groups I, II, III and VI revealed numerous regions with exceptionally high divergence between group I to III and group VI variants. Oligonucleotide primers universal for all the above groups of the virus were designed in conserved short stretches of sequences flanking the divergent regions in the helicase (Hel) and RNA-dependent RNA polymerase (RdRP) domains of the replicase gene and the divergent copy of the capsid protein (dCP) gene. Cloning and sequencing of the 549-bp RT-PCR amplicon of the helicase domain from grapevine cv. Shiraz lead to the detection of a variant of GLRaV-3, which shared only 69.6-74.1% nt similarity with other variants, including the recently reported, new, highly divergent variant, isolate 139. This was confirmed by the results of the analysis of 517-bp amplicon of the HSP70 gene of GLRaV-3 generated in RT-nested PCR based on degenerate primers for the simultaneous amplification of members of the Closteroviridae family designed by Dovas and Katis (J Virol Methods, 109, 2003, 217). In this genomic region, the variant shares 72.3-78.7% nt similarity with other variants of GLRaV-3. This previously unreported, new, highly divergent variant was provisionally named GTG10. From the alignment of the HSP70 sequences primers for the specific RT-nested PCR amplification of the variant GTG10 and members of group VI, and specific simultaneous amplification of variants of groups I, II and III, were designed. The results obtained from brief testing of various grapevines using all these primers suggest a relatively limited presence of GTG10 variant in vineyards. © 2013 Blackwell Verlag GmbH.

Kilic T.,Plant Protection Research Institute
Phytoparasitica | Year: 2010

In August 2009, boring lepidopteran larvae were found on aerial parts of tomato (Lycopersicon esculentum Mill.) plants in the Urla District of Izmir Province within the Aegean Region of Turkey. Larvae created blotched leaf galleries and superficial mines on fruits. The pest was identified as Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae). This is the first report of this pest in Turkey. © 2010 Springer Science+Business Media B.V.

The genus Astichus Förster (Eulophidae: Entiinae) is recorded for the first time from sub-Saharan Africa and four new species are described from South Africa: A. micans n. sp., A. silvani n. sp., A. gracilis n. sp. and A. naiadis n. sp..Astichus species are known as parasitoids of Ciidae (Coleoptera) tunnelling and living in bracket fungi. The South African species emerged together with Ciidae from a variety of bracket fungi from many localities in the region. They are easily separated from known Astichus species from other regions in the world by their distinctive colour and patterning. A key to the South African Astichus species, distribution maps, and notes on biology are included, as well as identifications of Ciidae and bracket fungus specimens encountered in the study. Copyright © 2012 Magnolia Press.

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