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A genetic analysis of the species and intraspecific lineages of Dactylopius Costa (Hemiptera: Dactylopiidae)
Abstract and Figures
The Cactaceae family comprises 15 genera and nearly 2000 species. With one exception, these are all native to the Americas. Numerous cactaceous species are invasive in other parts of the world, resulting in considerable damage to ecosystem functioning and agricultural practices. The most successful biological control agents used to combat invasive Cactaceae belong to the Dactylopius genus (Hemiptera: Dactylopiidae), comprising eleven species. The Dactylopiidae are exclusively cactophagous and are usually host-specific. Some intraspecific lineages of dactylopiids, often referred to as `biotypes', also display host-specificity, and are used to control particular species of invasive Cactaceae. To date, two lineages within Dactylopius opuntiae (`ficus' and `stricta'), and two within D. tomentosus (`cholla' and `imbricata') have been released in South Africa to control Opuntia ficus-indica and O. stricta, and Cylindropuntia fulgida and C. imbricata, respectively. The `californica var. parkeri' lineage is currently under consideration for release in South Africa for the control of C. pallida. Australia has already released these five lineages, and approved the release of an additional three in 2017; namely D. tomentosus `bigelovii', `cylindropuntia sp.', and `acanthocarpa x echinocarpa'.
Many of the Dactylopius species are so morphologically similar, and in the case of lineages, identical, that numerous misidentifications have been made in the past. These errors have had serious implications, such as failed attempts at the biological control of cactus weeds. This thesis aimed to generate a multi-locus genetic database to enable the identification of the species and lineages in the Dactylopiidae family, and to test its accuracy. Seven species were included in the analysis, including two lineages within D. opuntiae and six within D. tomentosus. Genetic characterisation was achieved through the DNA sequencing of three gene regions; namely mitochondrial 12S rRNA and cytochrome c oxidase I (COI), nuclear 18S rRNA, and fragment analysis using two inter-simple sequence repeats (ISSRs). Nucleotide sequences were very effective for species-level identification, where the 12S, 18S, and COI regions showed 100%, 94.59%, and 100%
identification accuracy rates, respectively. Additionally, the 12S and COI markers distinguished between half of the D. tomentosus lineages (`californica', `cholla', and `imbricata'), with identification accuracies of 100%. The `echinocarpa x acanthocarpa', `bigelovii', and `cylindropuntia sp.' lineages formed one clade. None of the DNA genetic markers showed a separation between the `ficus' and `stricta' lineages within D. opuntiae. Fragment analysis through the use of ISSRs provided higher-resolution results, and addressed this gap by showing a well-supported separation between the two lineages, and between wild populations collected in the Eastern Cape Province in South Africa. The identification accuracy of the `ficus' and `stricta' lineages was 81.82%. This is the first time that a method has been developed that can distinguish between these lineages. An additional component of this thesis was the creation of three user-friendly R-based programs to assist with:
1. ISSR data processing.
2. The identification of query Dactylopius nucleotide sequences relative to the gene databases created here.
3. A graphical user interface (GUI) version of the R package `SPIDER', which is useful for the assessment of the accuracy of genetic barcode data.
A successful biological control programme relies on the correct identification of the agent in question, and so it is imperative that cactus biological control practitioners are able to distinguish between Dactylopius species and lineages in order to release the most effective ones onto target Cactaceae. The laboratory protocols reported, and data processing tools created here, have largely addressed this need and offer valuable practical applications. These include:
1. The flagging of potential new species, cryptic species, and lineages of dactylopiid species released as new biocontrol agents.
2. Validating the identifications made by taxonomists based on morphology.
3. Confirming to which species, and, where applicable, to which lineage, a field-collected sample belongs.
4. Identifying hybrids resulting from lineage crosses.
Ensuring that the correct Dactylopius species are utilised for biological control will improve the control of invasive Cactaceae and protect biodiversity and agricultural productivity.
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The purpose of this study was to construct the DNA fingerprinting and query system with which to identify mung bean varieties from Northeast China. Eight primer pairs for fluorescent‐labeled simple sequence repeat markers with high polymorphism and a strong discrimination ability were used to detect 151 mung bean varieties from Northeast China. A total of 59 bands were detected, ranging from 4 to 11 with an average of 7.4. An unweighted pair group method analysis was used to cluster the mung bean varieties into five separate groups according to their genetic characteristics, which were consistent with the results of principal component analysis. Unique identification cards and barcodes with which each variety can be identified were established according to fingerprinting. A query system was also established which can provide the information and genetic relationships among some indefinite variety and mung bean varieties from Northeast China. This research will significantly assist in identification, traceability management, protection of origin, and intellectual property rights. It will also provide essential technical support for revealing the level of genetic diversity for breeding and germplasm innovation of mung bean varieties in Northeast China. In this study, we screened out eight pairs of high polymorphic SSR primers to develop a powerful toolkit for genetic diversity analysis and SSR fingerprinting construction among 151 mung bean varieties from Northeast China which enriched the primer resources of mung bean for identification, traceability management, protection of origin, and intellectual property rights. It also provided essential technical support for revealing the level of genetic diversity and the degree of differentiation at the molecular level and providing a reference for breeding and germplasm innovation and rational utilization of mung bean varieties in Northeast China.
This review summarizes all known direct nontarget attack (NTA) cases of intentionally released or actively redistributed weed biological control agents, in order to allow for an objective risk-benefit analysis when choosing the most appropriate method for controlling invasive plants. Of 457 agents inten-. © 2019 by The University of Chicago Press. All rights reserved.
Australia and South Africa have a long history of sharing successful biocontrol agents for cactus weeds but other countries, such as Namibia, could also benefit. There are four biological control agents that are widely utilised in South Africa and/or Australia for the control of 10 invasive alien Cactaceae in Namibia.
Two biocontrol agents, a leaf-spot pathogen, Passalora ageratinae, and a stem gall fly, Procecidochares utilis, have been released against Crofton weed, Ageratina adenophora (syn. Eupatorium adenophorum) (Asteraceae), in South Africa. This work reports the first post-release evaluation of the effect of both agents acting together in the field. A greenhouse trial using both agents had predicted an additive (beneficial) interaction between the agents. This study investigated if the additive interaction was present in the field. Four month old stems were exposed to one of the following three treatments (n = 20 plants per treatment): pathogen-only, pathogen plus single fly-galled, and pathogen plus double fly-galled, for 11 months. The interaction between the agents was equivalent to both agents acting independently (i.e. there was no additive effect on the weed’s growth). The greenhouse trails were therefore not predictive of field conditions.
The conical snail, Cochlicella acuta, is a major introduced pest of grain crops in southern Australia. In particular, C. acuta aestivates on the heads and upper stalks of crop plants thus fouling grain harvests in late spring - early summer. Previous attempts to control this snail pest included the release, during the early 2000s, of parasitic flies (Sarcophaga villeneuveana) sourced from southern France, within the perceived native distribution of C. acuta. The flies established in southern Australia, but only in very low numbers, such that there was no significant reduction in the snail's pest status. Sequencing of the snail's COI and 16S mitochondrial genes has now identified three main maternal lineages within C. acuta, across its distribution in south-western Europe and Morocco. The 1st lineage was only found in north-eastern Spain (near the Pyrenees), throughout southern France and in northern Italy. Both the 2nd and 3rd lineages were found in the U.K., western France, northern and southern Spain, Portugal and Morocco. The 3rd lineage was also collected throughout eastern Spain and just into southern France (near the Pyrenees). All the C. acuta found in Australia belong to the 3rd lineage. Highest levels of genetic diversity in C. acuta were found in the 3rd lineage, in particular in Morocco. A plausible explanation for the poor performance of the biological control agent previously released to control C. acuta in Australia is a mismatch between snail host and selected parasitoid. A different biotype or sub-species of S. villeneuveana, or even a different parasitoid species altogether, that attacks the 3rd lineage of C. acuta in south-western Europe or Morocco, could prove to be a more effective biological control agent than the S. villeneuveana previously released from southern France. Climates in southern Spain, southern Portugal and northern Morocco also best match those areas in southern Australia where C. acuta is a pest, suggesting further searches for effective natural enemies should be focussed there.
Luther Burbank (1849–1926) was a prolific ornamental plant breeder, who worked with 91 genera of ornamentals, from Abutilon to Zinnia , and released nearly 1000 cultivars to the industry. His innovative work included both herbaceous and woody plant materials as well as ornamental vegetables such as corn, tomatoes, and spineless cacti. His most popular ornamental release, the shasta daisy hybrids—first released in 1901, is still on the global market. This article focuses on Luther Burbank’s breeding techniques with ornamental plants and how both the germplasms that he developed and his methodologies used permeate modern flower breeding. Genera with the highest number of cultivars bred and released by Burbank include Amaryllis , Hippeastrum , and Crinum followed by Lilium , Hemerocallis , Watsonia , Papaver , Gladiolus , Dahlia , and Rosa. With Lilium , he pioneered breeding the North American native lily species, particularly those from the Pacific coastal region, producing the eponymous Lilium × burbankii . Burbank’s breeding enterprise was designed to be self-sustaining based on profits from selling the entire product line of a new cultivar or crop only to wholesale firms, who then held exclusives for propagation and selling, although financial hardships necessitated selling retail occasionally. Entire lots of selected seedlings were sold to the highest bidder with Burbank setting the price in his annual catalogs such as the Burbank Hybrid Lilies lot for U.S. $250,000 or some of the “very handsome, hardy ones” for U.S. $250 to U.S. $10,000 each. Other flower cultivars also commanded high prices such as seedling Giant Amaryllis that sold for U.S. $1.55/bulb in 1909. Cacti were another area of emphasis (he released more than 63 cultivars) from the spineless fruiting and forage types ( Opuntia ficus-indica , O. tuna , O. vulgaris ) to flowering ornamentals such as O. basilaris , Cereus chilensis , and Echinopsis mulleri. Interest in cacti during 1909–15 rivaled the Dutch Tulip mania with exorbitant fees for a single “slab” of a cultivar, speculative investments, controversy with noted cacti specialists (particularly David Griffiths), and lawsuits by The Burbank Company. Although most cultivars have been lost, Burbank’s reputation as the Father of American Ornamental Breeding remains admirable from critics and devotees alike.
The Opuntia cochineal scale or false carmine cochineal scale, Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae), is spreading rapidly in many countries, especially in the Mediterranean basin, where it has become a serious pest of prickly pear crops, Opuntia ficus‐indica (L.) Miller (Cactaceae). This crop is an important food resource both for humans and livestock. The cochineal was originally used as a biological agent to control cactaceous weeds in many countries where Opuntiaceae had been introduced. Currently, in some countries where the prickly pear is no longer considered a weed but a productive crop, as in the Mediterranean area, D. opuntiae has changed its role from a highly prized biological control agent to the status of serious pest. This paper provides an overview of the current knowledge on D. opuntiae for farmers and stakeholders in order to indicate the most appropriate way to limit or counteract the spread of this pest especially in new cultivated areas. Originally used as a biocontrol agent against Cactaceae weeds, Dactylopius opuntiae (Hemiptera: Dactylopiidae) has turned into a serious pest in some countries where prickly pear is considered a productive crop, as in the Mediterranean basin. This paper focuses on the spread of D. opuntiae as a pest of the prickly pear cactus and on its taxonomy, biology, host plants, and role as a biological control agent. The damage it causes and the control strategies currently available are also reported.
Climatic incompatibility between source and intended release sites of biological control agents is frequently cited as a limiting factor to their establishment and proliferation, and ultimately the successful control of a target weed. Climate matching techniques have been used to overcome this limitation by prioritising regions in the target weed's native range to survey for climatically-matched control agents. However, climate matching has been criticised for not considering that climatically compatible regions may not contain host-plant populations, which is especially important for weeds with an unknown or uncertain native distribution. To overcome this limitation, an ecological niche modelling approach (MaxEnt) was used to identify “sweet-spots” to search for candidate biological control agents for two African grasses that are invasive in Australia, namely: Sporobolus pyramidalis P. Beauv. and S. natalensis (Steud.) Dur. & Schinz (Poaceae) (giant rat's tail grasses). “Sweet-spots” were identified by overlaying rasters indicative of climatic suitability for plant growth, reproduction and survival (i.e. models calibrated using native range occurrences) and climatic compatibility with intended biological control agent release sites in Australia (i.e. models calibrated using invaded range occurrences). This approach reduced the total geographic search area by 3.8–7.5 million km² (57–88% of the total search area), with respect to traditional climatic matching techniques. The models identified: eastern South Africa, eastern Madagascar, Ethiopia, Kenya and coastal West Africa (S. pyramidalis only) as high-priority regions to search for potentially climatically-matched biological control agents. These findings are discussed in the context of guiding and optimising the native range component of this biological control programme, and how this increases the likelihood of successfully managing weed infestations in Australia.