Yizhou Chen

Evidence of superclones in Australian cotton aphid Aphis gossypii Glover (Aphididae: Hemiptera)

BACKGROUND Aphis gossypii is an important pest of cotton that has developed resistance to many chemicals used for its control. Any lack of understanding of its genetic structure, resistance status and host plant specialisation hampers effective management. RSULTS Eight microsatellite markers were genotyped for a collection of Australian A. gossypii field isolates from 55 plant species from major Australian cotton-producing regions. The aphids pirimicarb resistance status linked to the ACE1 (acetylcholinesterase) S431F mutation was determined by PCR-RFLP. Overall, the genetic diversity was low and there were only 13 multilocus genotype (MLG) groups found in a total of 936 aphids, suggesting asexual reproduction. Three MLGs (Aust-01, Aust-02 and Aust-04) represented 78% of all aphids tested. MLGs Aust-01 (41%) and Aust-02 (18%) were linked to the ACE1 S431F mutation and found on cotton and a range of hosts. Aust-04 (19%) hosted mainly on cotton (but also Asteraceae and Malvaceae) was predominantly susceptible to pirimicarb. Given their abundance and widespread occurrence, these three clones were considered to be superclones. CONCLUSION The study demonstrated that any strategy to control A. gossypii and manage pirimicarb resistance should target A. gossypii strains of all MLG types residing on any plant species and not just cotton

Genetic and functional evaluation of the level of inbreeding of the Westran pig: a herd with potential for use in xenotransplantation

Abstract:  Background:  The Westran pig has been purposely inbred for use in xenotransplantation. The herd originated in the wild from a limited gene pool and has been inbred by repeated full‐sib matings for nine generations.

Improving the comparative map of porcine chromosome 10 with respect to human chromosomes 1, 9 and 10

ZOO-FISH mapping shows human chromosomes 1, 9 and 10 share regions of homology with pig chromosome 10 (SSC10). A more refined comparative map of SSC10 has been developed to help identify positional candidate genes for QTL on SSC10 from human genome sequence. Genes from relevant chromosomal regions of the public human genome sequence were used to BLAST porcine EST databases. Primers were designed from the matching porcine ESTs to assign them to porcine chromosomes using the INRA somatic cell hybrid panel (INRA-SCHP) and the INRA-University of Minnesota Radiation Hybrid Panel (IMpRH). Twenty-eight genes from HSA1, 9 and 10 were physically mapped: fifteen to SSC10 (ACO1, ATP5C1, BMI1, CYB5R1, DCTN3, DNAJA1, EPHX1, GALT, GDI2, HSPC177, OPRS1, NUDT2, PHYH, RGS2, VIM), eleven to SSC1 (ADFP, ALDHIB1, CLTA, CMG1, HARC, PLAA, STOML2, RRP40, TESK1, VCP and VLDLR) and two to SSC4 (ALDH9A1 and TNRC4). Two anonymous markers were also physically mapped to SSC10 (SWR1849 and S0070) to better connect the physical and linkage maps. These assignments have further refined the comparative map between SSC1, 4 and 10 and HSA1, 9 and 10.

Population genetic variability and origin of Auckland Island feral pigs

Abstract Genetic variability of pigs isolated on the remote Auckland Islands of New Zealand was examined using 26 microsatellites recommended by the International Society for Animal Genetics (ISAG) and the Food and Agriculture Organisation (FAO) for porcine biodiversity analysis. The diversity indices, including observed and effective numbers of alleles, and observed and expected heterozygosity, revealed that Auckland Island pigs have a low level of genetic variability compared with European, Asian, Middle American indigenous and commercial pigs, as would be expected for a small population isolated for up to 200 years. Phylogenetic analyses of microsatellite data suggest that Auckland Island feral pigs are more related to European pigs than Chinese pigs, consistent with mitochondrial control region sequence analyses. In addition, the UPGMA topology based on microsatellite allele sharing measures showed that genotypes alone could accurately assign all Auckland Island pigs to their correct population, and also that two distinct Auckland Island subpopulations could be recognised.

Assignment of suppressor of cytokine signalling-2 (SOCS2) to porcine chromosome 5 with radiation hybrids.

SOCS (suppressor of cytokine signalling) proteins, also known as SSI (stat-induced stat-inhibitor) proteins, are negative regulators of cytokine-induced signal transduction. Cytokines regulate cellular behaviour by interacting with receptors on the plasma membrane of target cells and activating intracellular signal transduction cascades such as the JAK-STAT pathway (Krebs and Hilton, 2000.) Metcalf et al. (2000) generated mice unable to express Socs2, to examine the function of the gene in vivo. Socs2–/– mice grew significantly larger than their wildtype littermates (Metcalf et al., 2000). Characteristics of deregulated growth hormone and insulin-like growth factor-1 (IGF-1) signalling were observed in the Socs2–/– mice, indicating that SOCS2 may have an essential negative regulatory role in the growth hormone/IGF-1 pathway (Metcalf et al., 2000). Greenhalgh et al. (2003) provided compelling evidence that the gigantism displayed in the Socs2–/– phenotype is a result of negative regulation of growth hormone (GH) signalling by creating Socs2–/– mice that were also deficient in endogenous growth hormone production due to a point mutation in the GH-releasing hormone receptor. These Socs2–/–Ghrhrlit/lit mice displayed almost double the response to exogenous growth hormone administration as Socs2+/+Ghrhrlit/lit mice. Genome sequences show that SOCS2 maps to human chromosome 12q (GenBank accession number NM003877) and mouse chromosome 10 (GenBank accession number NM007706). SOCS2 has not previously been mapped in the pig, and this is the first step in further investigation into the gene’s action in a large production animal. Materials and methods

A significant fitness cost associated with ACE1 target site pirimicarb resistance in a field isolate of Aphis gossypii Glover from Australian cotton

The aphid Aphis gossypii Glover is an important pest of Australian cotton and has developed resistance to many chemicals used for its control. Its resistance management is partially based on chemical rotation that relies on insecticide resistance being associated with fitness costs. Therefore, understanding fitness costs associated with insecticide resistance is critical to its sustainable resistance management. We studied the fitness cost of pirimicarb resistance in A. gossypii caused by a single mutation in the acetylcholinesterase gene ACE1 by mixing different ratios of susceptible and resistant aphids. This was achieved by establishing A. gossypii populations of a known starting allele frequency in aphid proof cages and measuring allele frequency change over time via qPCR. Unlike traditional cohort fitness studies, we used competitive fitness as a measure of relative fitness of resistant versus susceptible aphids in the same environment. We demonstrate that competitive fitness measured in this study is an accurate predictor of overall relative fitness. We found that pirimicarb resistance had a significant fitness cost in the presence of susceptible aphids in the absence of insecticide pressure and that the fitness cost was related to the initial resistance allele frequency. By using the competitive fitness measure and knowing the initial allele frequency, it is possible to predict the likely time from resistant to an essentially susceptible population. As resistance was stable in the absence of susceptible competition, we recommend the use of resistance management tactics that do not completely eliminate the susceptible genotype such as complimentary integrated pest management.

Baseline susceptibility and cross‐resistance in Aphis gossypii Glover (Aphididae: Hemiptera) to phorate and sulfoxaflor

Susceptible discriminating doses of phorate (0.2 g/L) and sulfoxaflor (0.01 g/L) against cotton aphid Aphis gossypii Glover were determined by laboratory bioassay where aphids were sprayed with insecticide with the aid of a Potter spray tower. All of the populations tested were susceptible to sulfoxaflor, and only a pirimicarb resistant strain had cross‐resistance to phorate. If phorate is used as a side dressing in Australian cotton for insect control, neither pirimicarb, or any other chemical associated with insensitive acetylcholinesterase type one resistance, should be used as the first foliar spray for any subsequent aphid control.

A TaqMan qPCR method for detecting kdr resistance in Aphis gossypii demonstrates improved sensitivity compared to conventional PCR–RFLP

Cotton aphid, Aphis gossypii Glover, has emerged as a prominent pest in Australian cotton production, and monitoring pesticide resistance including pyrethroids in field populations is crucial for its sustainable management. We examined the distribution of kdr resistance in 35 field-collected A. gossypii populations and used TaqMan qPCR assays with pooled samples. The study demonstrated proof of concept that pooled insect qPCR methodology provided effective detection with better sensitivity than individual PCR–RFLP genotyping techniques for the kdr resistance allele. The practical outcome is that routine resistance monitoring can examine more sites while increasing the likelihood of detecting incipient resistance at those sites. More importantly, the method is adaptable to any genetically caused resistance and so not limited to A. gossypii or even insect control. It cannot be overstressed that the ability to detected resistance at very low frequencies is critical to all sustainable resistance management. Early detection of resistance provides critical time for the modification of chemical use prior to potential insecticide control failure.

Assignment of UCK2, ATF3 and RGS18 from human chromosome 1 to porcine chromosomes 4, 9 and 10 with somatic and radiation hybrid panels.

Primer design Human mRNA sequences from UCK2 , ATF3 and RGS18 were used in a nucleotide Basic Local Alignment Search Tool (BLASTn, Version 2, 2.3) (http://www.ncbi.nlm.nih.gov/BLAST/) (Altschul et al., 1990) of the GenBank (http://www.ncbi.nlm.nih.gov) EST database to identify matching ESTs from pigs. Human genome sequence was used to predict the position and approximate size of the introns. Primers were designed on exons fl anking introns. The primers were designed using the Primer3 program (Rozen and Skaletsky, 2000) in ANGIS’s Biomanager (www. angis.org.au).

First detection of etoxazole resistance in Australian two-spotted mite Tetranychus urticae Koch (Acarina: Tetranychidae) via bioassay and DNA methods

Etoxazole is used in Australia to control mites on a range of crops including pome fruit and cotton. Although resistance has been widely reported elsewhere, it has not previously been detected in Australia. Here, we report the first detection of etoxazole resistance (>12 500 fold) in Australian two‐spotted mite Tetranychus urticae from pome fruit via both bioassay and DNA methods. It is envisaged that the DNA‐based method developed here can be used to monitor etoxazole resistance in T. urticae.