7 research outputs found
Aphid resistance in Medicago truncatula involves antixenosis and phloem-specific, inducible antibiosis, and maps to a single locus flanked by NBS-LRR resistance gene analogs
No full text© 2005 American Society of Plant BiologistsAphids and related insects feed from a single cell type in plants: the phloem sieve element. Genetic resistance to Acyrthosiphon kondoi Shinji (bluegreen aphid or blue alfalfa aphid) has been identified in Medicago truncatula Gaert. (barrel medic) and backcrossed into susceptible cultivars. The status of M. truncatula as a model legume allows an in-depth study of defense against this aphid at physiological, biochemical, and molecular levels. In this study, two closely related resistant and susceptible genotypes were used to characterize the aphid-resistance phenotype. Resistance conditions antixenosis since migratory aphids were deterred from settling on resistant plants within 6 h of release, preferring to settle on susceptible plants. Analysis of feeding behavior revealed the trait affects A. kondoi at the level of the phloem sieve element. Aphid reproduction on excised shoots demonstrated that resistance requires an intact plant. Antibiosis against A. kondoi is enhanced by prior infestation, indicating induction of this phloem-specific defense. Resistance segregates as a single dominant gene, AKR (Acyrthosiphon kondoi resistance), in two mapping populations, which have been used to map the locus to a region flanked by resistance gene analogs predicted to encode the CC-NBS-LRR subfamily of resistance proteins. This work provides the basis for future molecular analysis of defense against phloem parasitism in a plant model system.John Klingler, Robert Creasy, Lingling Gao, Ramakrishnan M. Nair, Alonso Suazo Calix, Helen Spafford Jacob, Owain R. Edwards and Karam B. Sing
Effects of Carbohydrate Foods on Foraging Decisions of the Parasitoid \u3ci\u3eBathyplectes curculionis\u3c/i\u3e (Thomson) (Hymenoptera: Ichneumonidae)
No full textIn a series of field and laboratory experiments, I explored the trade-off between self-maintenance and current reproduction for the parasitoid Bathyplectes curculionis (Thomson)(Hymenoptera: Ichneumonidae), an economically important natural enemy of the alfalfa weevil, the most significant pest in forage alfalfa. Floral nectars, pea aphid honeydew, and artificial foods such as sugar sprays are likely to assist B. curculionis in meeting its self-maintenance needs. Once these needs are met then B. curculionis females may be more likely to search for hosts to parasitize. However, these foods must not only be available, but accessible, of high quality, and detectable, to be of benefit to the wasp. Sugar sprays applied to alfalfa increased the number of B. curculionis adults throughout the first crop of alfalfa and elevated the rate of parasitism late in the first crop. A significant interaction between local abundance of aphids (and their honeydew) and the application of sugar spray indicated that sugar sprays may be redundant when numbers of pea aphids are high. In a Y-tube olfactometer, hungry wasps preferred odors of dandelions and fed wasps preferred the odor of the host plant, alfalfa, suggesting a readiness to host search only in fed wasps. Females did not behave similarly, however, when phacelia was substituted for dandelion as the floral odor source. The unfed wasps showed no preference for phacelia odor to that of alfalfa. Although the wasps lived significantly longer when fed dandelion nectar than phacelia nectar, surprisingly, neither availability of whole dandelions nor phacelia flowers had a notable impact on wasp longevity. Floral morphology probably limited access to the nectar. Virgin wasps outlived mated wasps when provided either dandelion or phacelia flowers. Wasps fed honey water lived much longer than wasps feeding at flowers; mated wasps fed honey lived longer than unmated wasps. Although pea aphid honeydew is a potential food in the field, it is unlikely that B. curculionis actively seeks out this food. Olfactometer experiments indicated that these wasps had no naïve response to the odor of pea aphids but can associatively learn pea aphid odor. But when the odors of pea aphids and alfalfa are mixed together, the wasp could not distinguish between alfalfa with pea aphids from alfalfa without aphids. A parasitoid\u27s competing needs for self-maintenance and current reproduction may be balanced if these wasps are provided with high-quality carbohydrate foods that are physically accessible, and easily located in close association with hosts
Variation in postdispersal weed seed predation in a crop field
No full textPostdispersal weed seed predation by animals during the summer fallow period may lead to a reduction in the number of weeds that grow in the following winter cropping season. In this study, we investigated the patterns of weed seed removal, the influence of crop residue cover on seed removal, the types of granivores present and their seed preferences in a 16-ha postharvest cropping field in Western Australia during the summer months over 2 yr. Seed removal from caches was extremely variable (from 0 to 100%). Removal rates were generally highest along the edges of the field near bordering vegetation and lowest in the center of the field and within the bordering vegetation. However, there were many deviations from this general pattern. There was no change in rates of predation with different levels of residue cover. Ants or other small invertebrates were found to remove the most seeds. However, seed removal by other animals, such as rodents, was also evident. Annual ryegrass seeds were preferred over wild oat seeds, followed by wild radish pod segments. Seed harvesting was lowest in late January, peaked in February, and decreased in March. Results from this study suggest seed harvesters could reduce the number of surface seeds in the field, reducing the weed seed bank. Management options that increase the activity of the seed harvesters may lead to less variability in seed predation and could, therefore, be incorporated into an integrated weed management program
Variation in postdispersal weed seed predation in a crop field
No full textPostdispersal weed seed predation by animals during the summer fallow period may lead to a reduction in the number of weeds that grow in the following winter cropping season. In this study, we investigated the patterns of weed seed removal, the influence of crop residue cover on seed removal, the types of granivores present and their seed preferences in a 16-ha postharvest cropping field in Western Australia during the summer months over 2 yr. Seed removal from caches was extremely variable (from 0 to 100%). Removal rates were generally highest along the edges of the field near bordering vegetation and lowest in the center of the field and within the bordering vegetation. However, there were many deviations from this general pattern. There was no change in rates of predation with different levels of residue cover. Ants or other small invertebrates were found to remove the most seeds. However, seed removal by other animals, such as rodents, was also evident. Annual ryegrass seeds were preferred over wild oat seeds, followed by wild radish pod segments. Seed harvesting was lowest in late January, peaked in February, and decreased in March. Results from this study suggest seed harvesters could reduce the number of surface seeds in the field, reducing the weed seed bank. Management options that increase the activity of the seed harvesters may lead to less variability in seed predation and could, therefore, be incorporated into an integrated weed management program
Dormancy release and germination of four mesquite (Prosopis spp.) morphotypes naturalized in Australia
No full textTurning back the tide - the invasive species challenge
No full textTerms of reference
Preface
On 26 March 2003 the Senate agreed to the recommendation of the Selection of Bills Committee in its Report No. 4 of 2003 that the Environment Protection and Biodiversity Conservation Amendment (Invasive Species) Bill 2002 be referred to the Environment Communications, Information Technology and the Arts Legislation Committee for inquiry and report by 25 November 2003.
It was subsequently agreed that there was merit in a more comprehensive examination of the general topic of the regulation, control and management of invasive species, and accordingly on 26 June 2003 the Senate agreed to refer the Bill to the Environment Communications, Information Technology and the Arts References Committee for examination in conjunction with a broad inquiry into invasive species with the following terms of reference:
(1) The regulation, control and management of invasive species, being non-native flora and fauna that may threaten biodiversity, with particular reference to:
(a) the nature and extent of the threat that invasive species pose to the Australian environment and economy;
(b) the estimated cost of different responses to the environmental issues associated with invasive species, including early eradication, containment, damage mitigation and inaction, with particular focus on:
the following pests:
(A) European fox (Vulpes vulpes),
(B) yellow crazy ant (Anoplolepis gracilipes),
(C) fire ant (Solenopsis invicta),
(D) cane toad (Bufo marinus), and
(E) feral cat (Felis catus) and pig (Sus scrofa), and
the following weeds:
(A) mimosa (Mimosa pigra),
(B) serrated tussock (Nassella trichotoma),
(C) willows (Salix spp.),
(D) lantana (Lantana camara),
(E) blackberry (Rubus fruticosus agg.), and
(F) parkinsonia (Parkinsonia aculeata);
(c) the adequacy and effectiveness of the current Commonwealth, state and territory statutory and administrative arrangements for the regulation and control of invasive species;
(d) the effectiveness of Commonwealth-funded measures to control invasive species; and
(e) whether the Environment Protection and Biodiversity Conservation Amendment (Invasive Species) Bill 2002 could assist in improving the current statutory and administrative arrangements for the regulation, control and management of invasive species
Rethinking North–South Research Partnerships Amidst Global Uncertainties: Leveraging Lessons Learned from UK GCRF Projects during COVID-19
No full textInternational research and development projects (or grand challenge projects) consist of multicultural, multi-country, multi-sectoral, and multi-stakeholder initiatives aimed at poverty reduction. They are usually conceived as partnerships between actors in the global north–south. The COVID-19 pandemic was a major unexpected disruption to ongoing projects and challenged their already complex management. The aim of this paper is to present evidence on how international development projects were impacted by COVID-19 with a particular focus on the relationship between research institutions in the north and south. We conducted a mixed-methods research study, combining a reflective exercise with the co-author team and a survey with principal investigators, project managers, and capacity development leads drawn from 31 Global Challenges Research Fund (GCRF) projects funded through the UK government’s Official Development Assistance (ODA) and focused on social–ecological system research. The survey contained closed- and open-ended questions in order to (i) demonstrate how those involved in managing projects adapted to risks, including both threats and opportunities, presented by the COVID-19 pandemic, and (ii) consider the implications for tailoring adaptive management approaches in international research projects amidst uncertainties, with a special focus on enhancing equities in global north–south partnerships. The paper offers the following recommendations on designing, planning, and implementing international research and development projects: (i) devolve project management in order to enhance project resilience and improve north–south equities; (ii) allocate dedicated resources to enable equitable north–south research partnerships; (iii) rely more on hybrid and agile approaches for managing a project’s life cycle; and (iv) improve resource flexibility, transparency, and communication through enhanced funder–implementer collaboration
