ORCID Profile
0000-0002-5405-3912
Current Organisation
NSW Department of Primary Industries
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Publisher: Wiley
Date: 20-04-2021
DOI: 10.1111/EVO.14217
Abstract: In females of haplodiploid animals, female production requires fertilization, whereas male production does not. Therefore, haplodiploid species can display extraordinary sex ratios. Constrained sex allocation occurs when a female cannot produce daughters. This can be due to virginity but may also occur after mating due to insemination failure, selfish genetic elements or physiological constraints. Here, we investigated the mechanism underlying constrained sex allocation in Pezothrips kellyanus. In this species some mated females produce highly female-biased broods, yet, for unknown reasons, others produce extremely male-biased broods. Using crossing experiments controlled for maternally inherited endosymbionts we confirmed that constrained females were successfully inseminated. Furthermore, male-biased offspring production was not paternally inherited, ruling out paternal sex ratio elements previously identified as sex ratio distorters in some parasitoid wasps. Next, we excluded mating time and paternal fitness effects (male size) on sex allocation. However, we found that constrained sex allocation only occurred in small females producing smaller eggs than large females producing larger eggs and female-biased broods. Consequently, the bimodal sex allocation pattern correlates with maternal condition, and may have arisen (adaptively or non-adaptively) in association with an egg size-mediated fertilization mechanism recently detected in some haplodiploids, with egg size positively affecting fertilization success.
Publisher: Springer Science and Business Media LLC
Date: 04-2021
DOI: 10.1007/S11033-021-06372-3
Abstract: Western flower thrips, Frankliniella occidentalis is an economically important agricultural pest. It causes damage by feeding and oviposition or indirectly by plant virus transmission. Australian F. occidentalis are resistant to many insecticides including spinosad and the related chemical spinetoram. Spinetoram resistance to F. occidentalis has been recently reported in three different Australian States, however, mechanisms conferring that resistance have not been investigated. To identify the mechanisms underlying resistance to spinetoram in F. occidentalis, we sequenced the genomic region of nicotinic acetylcholine receptor Foα6 in number of spinosad and spinetoram resistant field-populations. We found that a single nucleotide substitution (G to A) in exon 9 of the α6 subunit was present in resistant strains (G275E) and absent from susceptible. By examining field populations we consider the G275E mutation is the major cause of resistance to spinetoram in Australian F. occidentalis. We developed a real-time PCR diagnostic assay to quickly identify resistant alleles in field-populations. The method was used to test spinetoram resistant F. occidentalis collected from Australian cotton during the 2018-2019. Results show thrips tested carried the G275E mutation and the resistance allele was unusually widely distributed. The wide distribution of G275E mutation was not expected because spinetoram is not extensively used in Australian cotton. We speculate resistance may relate to extensive chemical use in crops nearby such as horticulture where thrips are often targeted for control. Our molecular diagnostic assay can provide timely and precise resistance frequency information that can support sustainable chemical use including spinetoram based IPM.
Publisher: Wiley
Date: 03-04-2020
DOI: 10.1111/AEN.12457
Publisher: Springer Science and Business Media LLC
Date: 22-02-2015
Publisher: Springer Science and Business Media LLC
Date: 17-10-2016
Publisher: Elsevier BV
Date: 2008
Publisher: Elsevier BV
Date: 2008
Publisher: Wiley
Date: 11-03-2017
DOI: 10.1111/EVO.13197
Abstract: Cardinium and Wolbachia are common maternally inherited reproductive parasites that can coinfect arthropods, yet interactions between both bacterial endosymbionts are rarely studied. For the first time, we report their independent expression of complete cytoplasmic incompatibility (CI) in a coinfected host, and CI in a species of the haplodiploid insect order Thysanoptera. In Pezothrips kellyanus, Cardinium-induced CI resulted in a combination of male development (MD) and embryonic female mortality (FM) of fertilized eggs. In contrast, Wolbachia-induced CI resulted in FM together with postembryonic mortality not previously reported as a CI outcome. Both endosymbionts appeared to not influence fecundity but virgins produced more offspring than mated females. In coinfected in iduals, Wolbachia density was higher than Cardinium. Wolbachia removal did not impact Cardinium density, suggesting a lack of competition within hosts. Maternal transmission was complete for Wolbachia and high for Cardinium. Our data support theoretical predictions and empirical detection of high endosymbiont prevalence in field populations of the native range of this pest thrips. However, previous findings of more frequent loss of Wolbachia than Cardinium, particularly in field populations of the host's invasive range, suggest that genetic ersity or varying environmental factors between field populations also play a role in shaping host-endosymbiont dynamics.
Publisher: Wiley
Date: 08-09-2021
DOI: 10.1111/AEN.12570
Abstract: Fall armyworm ( Spodoptera frugiperda ) has recently been detected in Australia. Globally, S. frugiperda is reported to be resistant to insecticides, including those permitted for its control by the Australian Pesticides and Veterinary Medicines Authority. Consequently, an understanding of the insecticide resistance status of newly migrated S. frugiperda into Australia, as well as an ability to accurately identify newly hatched larvae, would facilitate sustainable management. To aid identification, we developed a real‐time polymerase chain reaction diagnostic assay that can identify S. frugiperda species, irrespective of life stage, and distinguish between the rice and corn strains. We then screened S. frugiperda in iduals from Queensland, Western Australia, the Northern Territory and New South Wales for mutations causing target site insensitivity in the acetylcholinesterase (AChE) gene, the voltage‐gated sodium channel gene and the ryanodine receptor gene. In the populations tested, we found that mutation at positions A210S and F290V in AChE were common. These mutations are known to be associated with carbamate and organophosphate resistance in S. frugiperda outside Australia. In contrast, no mutation was found in gene voltage‐gated sodium channel causing pyrethroid resistance or the ryanodine receptor gene associated with diamide resistance. As S. frugiperda is new to Australia, the wide distribution of mutations in the AChE gene associated with organophosphate/carbamate resistance suggests that the original migrated S. frugiperda moths may have carried the mutations from outside Australia. As resistance genes have been detected, it is important to continue to monitor the resistance status of Australian S. frugiperda and further integrate complementary bioassay when available. Finally, as pesticide resistance is possible, it should be additionally considered when making pest management decisions and any spray failure should be followed by a pesticide from a different chemical group.
Publisher: Springer Science and Business Media LLC
Date: 03-02-2022
DOI: 10.1038/S41437-022-00505-5
Abstract: Maternally inherited bacterial endosymbionts that affect host fitness are common in nature. Some endosymbionts colonise host populations by reproductive manipulations (such as cytoplasmic incompatibility CI) that increase the reproductive fitness of infected over uninfected females. Theory predicts that CI-inducing endosymbionts in haplodiploid hosts may also influence sex allocation, including in compatible crosses, however, empirical evidence for this is scarce. We examined the role of two common CI-inducing endosymbionts, Cardinium and Wolbachia , in the sex allocation of Pezothrips kellyanus , a haplodiploid thrips species with a split sex ratio. In this species, irrespective of infection status, some mated females are constrained to produce extremely male-biased broods, whereas other females produce extremely female-biased broods. We analysed brood sex ratio of females mated with males of the same infection status at two temperatures. We found that at 20 °C the frequency of constrained sex allocation in coinfected pairs was reduced by 27% when compared to uninfected pairs. However, at 25 °C the constrained sex allocation frequency increased and became similar between coinfected and uninfected pairs, resulting in more male-biased population sex ratios at the higher temperature. This temperature-dependent pattern occurred without changes in endosymbiont densities and compatibility. Our findings indicate that endosymbionts affect sex ratios of haplodiploid hosts beyond the commonly recognised reproductive manipulations by causing female-biased sex allocation in a temperature-dependent fashion. This may contribute to a higher transmission efficiency of CI-inducing endosymbionts and is consistent with previous models that predict that CI by itself is less efficient in driving endosymbiont invasions in haplodiploid hosts.
No related grants have been discovered for Duong Thi Nguyen.