Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Has files: YesSubject: search.filters.subject.Resistance

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Genomic architecture of resistance to latania scale (H. lataniae) in kiwifruit (A. chinensis var. chinensis)
    (BioMed Central Ltd, 2023-10-31) Flay C; Tahir J; Hilario E; Fraser L; Stannard K; Symonds V; Datson P
    BACKGROUND: Latania scale (Hemiberlesia lataniae Signoret) is an armoured scale insect known to cause damage to kiwifruit plants and fruit, which ultimately reduces crop values and creates post-harvest export and quarantine issues. Resistance to H. lataniae does exist in some commercial cultivars of kiwifruit. However, some of the commercial cultivars bred in New Zealand have not inherited alleles for resistance to H. lataniae carried by their parents. To elucidate the architecture of resistance in the parents and develop molecular markers to assist breeding, these experiments analysed the inheritance of resistance to H. lataniae from families related to commercial cultivars. RESULTS: The first experiment identified a 15.97 Mb genomic region of interest for resistance to H. lataniae in rtGBS data of 3.23 to 19.20 Mb on chromosome 10. A larger population was then QTL mapped, which confirmed the region of interest as the sole locus contributing to H. lataniae resistance. inDel markers mapping the region of low recombination under the QTL peak further narrowed the region associated with H. lataniae resistance to a 5.73 Mb region. CONCLUSIONS: The kiwifruit populations and genomic methods used in this study identify the same non-recombinant region of chromosome 10 which confers resistance of A. chinensis var. chinensis to H. lataniae. The markers developed to target the H. lataniae resistance loci will reduce the amount of costly and time-consuming phenotyping required for breeding H. lataniae scale resistance into new kiwifruit cultivars.
  • Thumbnail Image
    Item
    Renters’ voices : the lived experience of young adults renting in Wellington City : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Psychology at Massey University, Albany, New Zealand
    (Massey University, 2023) Stephenson, Lucy Charlotte
    In this research project I explore and give voice to the experience of rental life for a group of young adults aged 18-25 years, renting in the private rental sector (PRS) in Wellington city, New Zealand (NZ). In the current economic climate, renting has become increasingly unaffordable, with insufficient supply creating a pressured market, extremely difficult for tenants to navigate. This study, based on an ontological and epistemological foundation of critical realism, and using reflexive thematic analysis (RTA), explores rental life for 14 participants through focus group interviews. It considers ways an asymmetric power imbalance in landlord/tenant relationships plays out in the lives of tenants. How landlord/tenant power dynamics influence the ability of participants to obtain security and a sense of home within their rental housing, with ongoing implications for mental health and wellbeing. It also considers how participants respond to their relative powerlessness with resistance and through strategies to maximise success. Four main themes and 10 subthemes were produced. The participants experienced ongoing high levels of difficulty and stress. They did not consider their rental properties to be homes although considerable evidence of home-making practices was evident. A lack of security, autonomy and agency within their rented dwellings could be seen as eroding their sense of home and wellbeing. In response participants formed strong bonds with each other, their lack of security in housing apparently compensated for by security in each other, and the emergence of a nomadic urban culture. The power imbalance in landlord/tenant relationships frequently resulted in conflict around maintenance and repairs. Participants chose carefully which battles to fight, frequently avoiding conflict. A high level of mobility was evident as a strategy for avoiding conflict and achieving better quality housing. Fixed term tenancy contracts while considered normal created major difficulties for participants. The Tenancy Tribunal was used in cases of serious difficulty, and some incidents of everyday resistance were evident, however, open resistance to landlord power was absent, a mark of the powerlessness of tenants in a system which relies on tenants to police it, while being simultaneously vulnerable to landlords through their need for positive tenancy references.
  • Thumbnail Image
    Item
    Development of an in vitro assay to screen Agathis australis (kauri) for resistance to Phytophthora agathidicida : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Herewini, Echo
    The iconic Agathis australis (kauri) of New Zealand, is under serious threat from kauri dieback disease caused by the soil-borne pathogen Phytophthora agathidicida. Infected kauri express symptoms of root and collar rot, bleeding resins at the base of the trunk, yellowing of foliage, canopy thinning, and tree mortality. Phytophthora agathidicida was first associated with kauri decline in 1972, where it was initially identified as P. heveae however, there was some uncertainty about its significance and taxonomy. The pathogen was officially identified as a new organism in 2008 and was called Phytophthora taxon Agathis until its formal description as Phytophthora agathidicida in 2015. This pathogen is easily vectored through root to root contact and mobile zoospores. Management and research has focused on mapping pathogen distribution, reducing spread, improving detection, ex situ conservation and clonal production using tissue culture techniques. In order to gain better understanding of the disease epidemiology and to develop better breeding programmes, a reliable in vitro resistance screening assay is required. This research focused on the development of a screening assay using detached leaves from tissue culture material as a means of accelerating screening assays compared to the more labour-intensive root inoculation assays. Foliar inoculations and assessment techniques were initially optimised on kauri leaves from tissue culture lines. The most successful inoculation method involved placing P. agathidicida-colonised agar plugs on wounded detached leaves. The assay was further tested on 2 year old kauri seedlings. Variation in susceptibility across kauri genotypes and leaf age, and variation in virulence among P. agathidicida isolates was observed. To further investigate the impact of leaf age on lesion extension, an assay was conducted on detached leaves from six rooted kauri saplings over 5 years of age, across three leaf age groups with P. agathidicida, P. multivora, and P. cinnamomi. Variation in virulence among these Phytophthora species was observed. Leaf necrosis was most severe with young tissue and susceptibility tended to decrease with increasing leaf age. Preliminary studies with 50 kauri clones identified different levels of susceptibility and tolerance across the different genotypes to P. agathidicida. The methods developed within this study have increased our understanding of the overall response of kauri to P. agathidicida foliar inoculations. This study demonstrated variation in the susceptability of kauri foliage to Phytophthora inoculation, although no complete resistance was observed. Further work is required to determine if there is a relationship between root and leaf responses which will help establish if in vitro genotypic variation can accurately predict natural genotypic variation seen within kauri forests.
  • Thumbnail Image
    Item
    Therapist relational skills and client resistance in a short motivational programme for offenders : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Clinical Psychology at Massey University, Albany, New Zealand.
    (Massey University, 2013) Provan, Hagan Ross
    Developing a better understanding of client resistance, and better evidence-based practise principles for dealing with resistance, have the potential to increase the efficacy of psychotherapy. There has been very limited research into client resistance, and even less which has investigated the link between therapist behaviours and resistance. The limited research to date has been conflicting and has primarily focused on narrowly operationalised definitions of resistance, as well as limiting measurement of therapist behaviours to therapist technical skills rather than interpersonal skills. There is little research investigating specific therapist relational skills that contribute to or reduce the likelihood of client resistance, and how this in-session interpersonal dynamic takes place. This study utilised a multi-method design to investigate the relationship between a number of therapist relational skills (therapist empathy-perspective taking, therapist empathy-attunement, and therapist resistance) and client resistance. Resistance was defined as oppositional behaviour within the session, or lack of engagement with the other member of the dyad, and perceived as the outcome of an interpersonal process. DVDs of therapy sessions were accessed from a from a Short Motivational Programme run by the Department of Corrections in New Zealand. Each of the DVDs was coded on a minute by minute basis, using measures of therapist interpersonal skills and client resistance. The study also measured the working alliance. The analysis combined: a group analysis of broad patterns across the dyads; a single case analysis involving a visual analysis of graphed data, supplemented with descriptive statistics; and a narrative analysis of client-therapist dialog. The results showed that therapist resistance and client resistance were strongly and positively related. The relationship between the two variables was also found to be temporally proximal at the level of a one minute segment. There was also a strong, but inverse relationship, between therapist empathy and client resistance, and again, the relationship was temporally proximal at the level of the one minute segment. Therapist resistance, especially, was closely synchronised to client resistance in terms of the timing of onset and cessation, and was also synchronised in terms of the level (intensity) of the two measures. The findings provide evidence for the idea that client resistance is often the result of an interpersonal dynamic, rather than simply an intrapersonal characteristic, and can be contributed to by poor therapist relational skills. The results showed that either therapist or client resistance can appear first, and tend to elicit resistance from the other member of the dyad (and lack of perspective taking by the therapist), which in turn elicits further resistance from the other dyad member. This appears to set in place a conflictual interpersonal dynamic that tends not to cease until the therapist stops resisting the client’s message, and takes a more empathic-perspective taking stance. The results also suggested that therapist perspective taking and therapist resistance may be specific interpersonal dynamics contributing to successful/unsuccessful therapist confrontations.
  • Thumbnail Image
    Item
    Variation in susceptibility of giant buttercup (Ranunculus acris L. subsp. acris) populations to herbicides : a thesis presented in partial fulfillment of the requirements for the degree of Master of AgriScience in Agriculture at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Lusk, Carolyn Sarah
    Giant buttercup (Ranunculus acris L.) is a serious weed of dairy pastures throughout New Zealand causing substantial economic losses from lost pasture productivity. It has developed resistance to the phenoxy herbicides (MCPA and MCPB) at many sites around New Zealand, particularly in Golden Bay. Since the discovery of resistance in the 1980s, two newer herbicides from a different mode-of-action group (acetolactate synthase inhibitor, ALS), flumetsulam and thifensulfuron-methyl, have been used widely, which appeared to overcome the resistance problem. A survey of farmers in Golden Bay indicated that most have herbicide control programmes for giant buttercup based around flumetsulam but some have reported poor control with this herbicide, particularly after several years of use. The research in this thesis was undertaken to determine whether this may be due to evolved resistance. Seedling progeny from 15 populations of giant buttercup, with known spraying history, were sprayed with a range of doses of flumetsulam, thifensulfuron-methyl and MCPA (Experiment 1) to test for differences in susceptibility. The experiment revealed a large difference in susceptibility between the populations (83-100% and 58-100% mortality at the recommended rate and 2.2 times that rate of flumetsulam applied, respectively). The population with the highest past exposure to flumetsulam showed the lowest mortality and 25% of plants in this population survived a treatment with 5 times the recommended rate. There was a significant declining trend between percent mortality and historical exposure of these populations to flumetsulam. However, most populations with low previous exposure had no or few resistant individuals and only a few populations with high previous exposure had several resistant individuals present, as indicated by their survival above recommended rates. Calculated LD50 values did not correlate well to the survival data or to historical exposure to flumetsulam, because the herbicide rates chosen in this experiment were too high. Measurements of the biomass of giant buttercup, obtained several times after spraying in Experiment 1, showed some evidence of cross resistance to thifensulfuron-methyl but not to MCPA. Biomass yields 3 months after treatment were 1, 2 and 22% of untreated for the recommended rates of flumetsulam, MCPA and thifensulfuron respectively, indicating that flumetsulam and MCPA were equally effective, but that thifensulfuron-methyl was less effective. In Experiment 2, plants from the most resistant and susceptible populations in Experiment 1, were grown from spare seeds and treated with a wider range of doses (including lower doses) of flumetsulam than in Experiment 1. The LD50 values for the two populations in this second experiment differed 5.3-fold and this difference was highly significant. Twenty-nine percent of plants from the population with high past exposure survived treatment with 25 times the recommended rate of flumetsulam compared to 0% from the population with no past exposure. In a third experiment the same three herbicides and rates were compared for their damage to perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) sown either in pots (Exp. 3a), or transplanted from the field (Exp. 3b). The total clover yield harvested over 5 months from newly-sown pasture was 80, 59 and 4% that of the untreated control for flumetsulam, thifensulfuron-methyl and MCPA applied at recommended rates, and 95, 40 and 30% respectively for transplanted swards. The total yield of grass was not reduced by any of the herbicides. Overall flumetsulam was the least pasture-damaging herbicide, but rates could not be increased above recommended rates in order to deal with resistance because pasture damage occurred. The experiments in this study indicate that resistance to flumetsulam may be evolving in giant buttercup in dairy pastures in Golden Bay, but more research is needed in field trials to confirm this. Furthermore, the results indicate that some populations may no longer be resistant to MCPA, but this also needs further study to confirm. Currently-available herbicides may not provide adequate control of giant buttercup in the future if existing management practices continue.