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Evaluation of mycoparasitic fungi as potential biological control agents of wattle rust (Uromycladium acaciae)
(2024) Poswa, Nonkululeko.; Laing, Mark Delmege.; Sivparsad, Benice Jenine.
Uromycladium acaciae (Cooke) P. Syd. & Syd., the causative agent of wattle rust, is an economically significant pathogen affecting black wattle (Acacia mearnsii De Wild) in the Republic of South Africa (RSA). Initial symptoms are brown powdery pustules on petioles, stems, and leaves which further develop into matting of leaves and pinnules, and rachis malformation. In severe cases, infection results in stunting of seedlings and mortality of young trees. Yield losses of up to 40% have been reported. The current control measures for wattle rust consist of azoxystrobin and triazole-based fungicides and the deployment of resistant or tolerant lines of A. mearnsii. However, due to undesirable environmental effects posed by fungicides, the substantial costs involved with both fungicide usage and the deployment of tolerant clones of A. mearnsii and increasing regulations around the use of fungicides in commercial forestry, there is a need for alternative control methods for wattle rust. The use of biological control presents a cost-effective and environmentally friendly alternative method for the management of wattle rust. Several mycoparasites of various rust diseases have been evaluated on different rust diseases as potential biological control agents. In this study, the mycoparasites Sphaerellopsis filum (Biv.- Bern. ex Fr.) Sutton [=Darluca filum (Biv.-Bern. ex Fr.) Berk.] and Akanthomyces uredinophilus Manfrino et al. were evaluated for biocontrol efficacy on wattle rust using an in vitro detached leaf assay. Leaves of black wattle infected with U. acaciae were collected from a local commercial plantation in Richmond, KwaZulu-Natal, South Africa. Rust-infected leaves were sprayed with conidial suspensions of 1 g.L-1 of S. filum (5.8x108 conidia.ml-1) and A. uredinophilus (1x106 conidia.ml-1) and incubated in plastic containers containing moist paper towels to create conditions of high humidity. Colonisation of rust pustules by A. uredinophilus and S. filum was assessed under a light microscope and a percentage colonisation for each treatment was estimated at four weeks post-inoculation. Colonised leaves were also viewed under an environmental scanning electron microscope (ESEM) to examine the interaction between the mycoparasitic fungi and U. acaciae. At four weeks post inoculation, A. uredinophilus and S. filum were able to colonise 41% and 44% of rust pustules, respectively. Under the ESEM, S. filum and A. uredinophilus demonstrated mycoparasitic activity on the teliospores of U. acaciae. Hyphae of S. filum and A. uredinophilus coiled around and punctured rust teliospores, causing them to rupture and deflate. Overall, conidia of both S. filum and A. uredinophilus were able to colonise and mycoparasitize U. acaciae teliospores. Optimal Integrated Pest Management (IPM) for disease suppression requires the seamless and coordinated integration of multiple compatible control strategies. Therefore, any biological agents that may be considered for use to suppress a disease should be compatible with the range of agrochemicals and adjuvants that are being used on the crop of interest, in order for the management strategy to be effective. To this end, the compatibility of two isolates of mycoparasitic fungi (Sphaerellopsis filum and Akanthomyces uredinophilus) and a commercial insect-pathogenic fungus (Beauveria bassiana, Eco-Bb®) with an insecticide (deltamethrin) and an adjuvant (Break-thru®) was evaluated. The experiment utilized an amended bioassay method with S. filum, A. uredinophilus, and B. bassiana being cultured on potato dextrose agar (PDA) amended with 250 μl.L-1, 125 μl.L-1 , and 500 μl.L-1 of Break-thru® , or amended with 1 ml.L-1, 0.5 ml.L-1 and 2 ml.L-1 of deltamethrin. Unamended media served as a negative control, whilst media amended with the commercial rust fungicide Amistar Top® served as a positive control. After three weeks, radial growth was measured from the centre of the fungal colony, and a percentage inhibition efficiency (IE) of Breakthru ®/ deltamethrin on the growth of the biological control agent was calculated. There was no significant inhibition in any of the biological agents by either Break-thru® or deltamethrin at all dosages tested. Therefore, S. filum, A. uredinophilus and B. bassiana are compatible with the insecticide (deltamethrin) and the adjuvant (Breakthru
®), and they could be combined in an integrated control program. Further evaluation of the two mycoparasitic fungi as potential biological control agents of wattle rust were undertaken in nursery pot trials. Pot Trial One investigated the biological control efficacy of mycoparasitic strains of S. filum and A. uredinophilus for control of wattle rust on three wattle varieties. Rust-infected cuttings of varieties PSO14, FW54 and SP644 were treated with S. filum and A. uredinophilus every two weeks for 12 weeks. They were also evaluated for rust levels every two weeks, as percentage leaf area infected. Experimental controls included a fungicide control (positive control) and untreated rust control (negative control). Bi-weekly applications of S. filum significantly reduced (p< 0.001) rust disease progression. Although applications with A. uredinophilus did reduce disease progression, it did not produce a significant reduction compared to the untreated rust control. After six and nine weeks of bi-weekly treatment applications, characteristic white mycelial growth of A. uredinophilus and S. filum, respectively, were observed on rust pustules. Characteristic spore morphology that resembled that of S. filum and A. uredinophilus was confirmed after re-isolation. There was no significant difference (p= 0.09605) between the wattle varieties in their response to the treatments. Overall, both S. filum and A. uredinophilus have the potential to control wattle rust.
In Pot Trial Two, the optimal dosage and application frequency of S. filum and A. uredinophilus was evaluated on the FW54 (susceptible, frost tolerant) commercial wattle variety. Conidial suspensions of the mycoparasitic strains were prepared at dosages of 1 2 x, 1x and 2x at a quantity of 5x105 conidia.ml-1, 1x106 conidia.ml-1, and 2x106 conidia.ml-1 of A. uredinophilus, and 0.5 gram, 1 gram and 2 gram.L-1 of S. filum (5.8 x 108 conidia.ml-1). The conidial suspensions were sprayed at three frequencies which were once-off, bi-weekly (every two weeks), and monthly. Prior to every biweekly spray treatment, percentage rust severity (0 to 100%) was scored for all treatment frequencies on the fully expanded leaves directly below the new flush. The percentage rust severity was used to calculate the area under disease progress curve (AUDPC). For S. filum and A. uredinophilus, dosage and frequency of application had no significant interaction. All treatments reduced wattle rust relative to the untreated control treatment. Notably, the bi-weekly treatment with a 2x dosage of A. uredinophilus resulted in the least amount of rust disease, which was not significantly different to that of the fungicide treated control.
In Pot Trial Three, the use of silicon fertilization in conjunction with A. uredinophilus (the best performing biocontrol treatment as identified in Pot Trial Two) for optimal control of wattle rust was evaluated. A spray application of 2x106 conidia.ml-1 of A. uredinophilus was combined with silicon fertilization at concentrations of 100, 200, and 400 mg.L-1 for evaluation of the control of wattle rust on the commercial wattle variety FW54. The A. uredinophilus spore suspension was sprayed bi-weekly (every two weeks), and treated seedlings were drenched every week with 10L of water containing silicon at 100, 200, and 400 mg L-1. Prior to every bi-weekly A. uredinophilus spray treatment, percentage rust severity (0 to 100%) was scored on the fully expanded leaves directly below the new flush. Experimental control treatments included a fungicide control (positive control, Amistar® Top, Syngenta) and an untreated rust control (negative control). At 16 weeks, leaf samples were taken from seedlings to evaluate the uptake and distribution of silicon using Field Emission Gun-Environmental Scanning Electron Microscopy (FEG-ESEM) and Energy Dispersive X-ray Spectroscopy (EDX). All treatments reduced wattle rust relative to the untreated control treatment. Treatment with A. uredinophilus + 400mg.L-1, silicon resulted in the least amount of rust disease. However, the A. uredinophilus + 0mg.L-1 silicon treatment also produced a significant reduction in rust. The EDX spectra and mapping showed that silicon was not taken up by treated plants. The combined application of A. uredinophilus and silicon fertilization did not result in the enhanced control of wattle rust because wattle appears not to take up silicon as a micronutrient. The overall results of this study suggest that both mycoparasites can be used as biological control agents for wattle rust. Bi-weekly applications of A. uredinophilus at 2x106 conidia.ml-1 was the best performing biocontrol treatment in these pot trials. However, it is unknown whether the nursery application of A. uredinophilus would yield sufficient fungal inoculum to control wattle rust under field conditions. Therefore, field trials should be implemented to establish the biocontrol efficacy of S. filum and A. uredinophilus under field conditions.
Negotiating identity: the experiences of black self-identified lesbian youth in township and rural contexts of KwaZulu-Natal.
(2024) Shabane, Prim-Rose Makhosazane.; Msibi, Thabo Perceviarence.
While lesbian, gay, bisexual and transgender (LGBT) youth face the typical challenges of South African youth, their lives are shaped by unique and complex experiences of
discrimination and marginalisation within the family, school and in cultural and religious settings. The study reported in this thesis explored the experiences of 12 black self-identified lesbian youth of school going age in township and rural contexts of KwaZulu-Natal. The study sought to explore how they construct and negotiate their experiences in the way that they do. This qualitative study was located within the interpretive paradigm and used a narrative inquiry design, with grounded conversations, focus group discussions, photovoice and diaries as data gathering tools. Six participants were selected through snowball sampling from rural contexts and six from township contexts. Ten were raised by their mothers and grandparents, one by her mother and adoptive father and the other one by her biological parents. The two theories that informed data analysis in the study were queer theory and the feminist theory of intersectionality. Queer theory became an appropriate tool in unpacking and understanding the multiple interpretations and fluidity of participants’ sexual identity. Intersectionality offered insight into how these youth’s experiences were caught up in inequalities of power related to gender, race, age, and social backgrounds. Ten themes and three sub-themes emerged in the findings: Firstly, it was family networks as
either supportive or demoralising and the three sub-themes, namely: a) difference enriching family relationships, b) children raised to think that they are useless, a shame and worthless and c) dysfunctional families and hatred of difference. Secondly, “Understandings of (absent) fatherhood”. The third theme was about the village failing to raise a child. The fourth was about schools as unsafe spaces. The fifth theme was on the teachers’ perspective about “Use the boys’ toilets because you are boys”. Sixth, other learners told them that “You are not competition; you need to be reminded that you are a girl”. The seventh theme was reminding the participants about their culture, “Behave properly, as expected in our culture”. The eighth theme exposed rejection and isolation: the cleansing of the sin. The ninth theme revealed participants’ assertion and self-esteem through sport, art and healing. The tenth theme highlighted the violence, trauma and resilience that were experienced by the participants. A major focus became my struggle in dealing with the traumatic situations of participants, situations I had not been prepared for, which pointed to the need for a fully reflexive approach to such research. The study concludes with the responses to the research questions, in particular the factors that led to the emphatic proclamation of a lesbian identity by participants, and with proposals for action and for further study.
Integration of educational technology resources in the teaching of grade 10-12 life sciences.
(2025) Thela, Zothani Minenhle.; Sokhulu, Lerato Hlengiwe.
The use of Educational Technology resources has brought numerous benefits in the education system such as enhancing the teaching and learning process. Furthermore, integrating educational technology resources fosters inclusive education and offers an engaged learning environment where learners acquire the 21st century skills relevant in this digital age. This study explored the integration of Educational Technology resources in the teaching of grade 10-12 Life Sciences. The study was carried out in four different high schools in the urban, rural and township of Eshowe town. This qualitative case study adopted the interpretive paradigm, involving four teachers purposively and conveniently selected. The study used reflective activities, one-on-one semistructured interviews and observations to generate data. The generated data was analysed using thematic analysis. The emerging themes formed the main findings of the study. In addition, Connectivism was employed as a philosophical lens to guide this study.
The findings of the study indicated that participants integrated similar hardware and software resources to teach Life Sciences. These included textbooks, overhead projectors, anatomical models, charts, laptops, videos and WhatsApp. The findings further reveal that participants were integrating these successfully in conjunction with the whole-class strategy but for different personal reasons. For instance, while some participants were using textbooks for assessing, others used them for visuals, and while other teachers were using OHPs to display notes some used them to display videos or pictures. Based on the study findings, it is recommended that teachers be equipped with more knowledge of other software and hardware resources such as YouTube, and apparatus. In addition, the study also recommends that teachers draw from the curriculum policies to integrate relevant educational technologies as formally prescribed.
Reflections on first year teaching by second year novice teachers.
(2024) Viljoen, Joranda.; Amin, Nyna.
The transition from novice to experienced teacher presents many challenges, notably during the induction phase, which significantly influences a teacher’s career trajectory. This study explores the experiences of second-year novice teachers, focusing on their reflections on their first year of teaching. novice teachers often face a stark reality shock as the classroom environment often differs from their expectations, with large class sizes, diverse student needs, and varying levels of resources across different school environments. A qualitative research design, rooted in the interpretive paradigm, was employed, using semistructured interviews and a single focus group discussion. Seven second-year teachers, who graduated from a private educational institution, participated in the study. The research aimed to identify the range of experiences, both positive and negative, that these novice teachers encountered, including the challenges they faced, the coping strategies they employed, and the support system that fostered their professional development. Key findings revealed a significant reality shock experienced by novice teachers due to the disparity between theoretical training and the practical demands of the classroom. Effective mentorship and professional development programs were identified as vital support systems that enhance novice teachers’ confidence and teaching efficacy. Moreover, the study revealed a plethora of positive experiences, such as supportive relationships and collaborative environments, which served as indispensable sources of emotional and professional support. Participants reported that mentorship and professional learning communities were invaluable in improving their classroom management skills and overall teaching competency. The implications of this research highlight the imperative need for effective support structures such as mentorship programs and professional learning communities to help novice teachers navigate the complexities of their early teaching years. Additionally, the findings stress the significance of improving training programs to better prepare novice teachers for the realities of the classroom. These recommendations are intended to promote teacher retention and optimise educational outcomes in South Africa.
Modeling economic growth for Nigeria using robust statistical models.
(2024) Ebiwonjumi, Ayooluwade.; Chifurira, Retius.; Chinhamu, Knowledge.
Economic growth is one of the most important goals of macroeconomic policy-making, but measuring it is not easy. This study aimed at measuring economic growth for Nigeria using robust statistical models. In this study, Gross Domestic Product (RGDP) is used as a proxy for economic growth and is modelled using selected predictors, namely internal debt (INDT), external debt (EXDT), interest rate (RINR), an exchange rate (REXR), and trade openness (OPEN). Quarterly RGDP index collected from the Central Bank of Nigeria for the period 1986 to 2022 was used in this study. Exploratory data analysis (EDA) revealed the linear relationship between the RGDP and the predictors. EDA also revealed the presence of multicollinearity and outliers in the predictors. In the presence of outlier and multicollinearity, this study utilizes the ridge regression, robust principal component regression, partial least square regression, average centered penalized regression, gaussian process regression and the coupler FMKL-GLD quantile regression. The performance and the efficiency of the adopted methods were evaluated using forecasting accuracy metrics, namely the root mean square error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE). In using robust PCR, it can be asserted that the robust principal component regression (M-estimator) technique was an efficient and optimal technique for predicting RGDP. Specifically, PC1 and PC2 account for 35.39% and 22.15% in RGDP. In PLS, non-cross-validated and cross-validated PLS selection methods were used. Thus, 91.5% of the variance in economic growth drivers were explained by the five components generated and selected from the non-cross-validated PLS method. While, 72.6% of the variance in economic growth drivers were explained by the two components generated and selected from the cross-validated PLS method. Hence, after the cross-validation and extraction, the first and second components were efficient and optimally predicted 63.1% and 18.4% economic growth. In the average centered penalized regression model, the performance of the LASSO, ridge and elastic net techniques were compared. Using the least value of the forecasting metric values, the LASSO-average centered penalized regression was robust. The result of the best-performing average-centered penalized regression model indicated that INDT, RINR, REXR and OPEN positively contributed to the RGDP by 4.27%, 0.40%, 0.49% and 0.52% respectively. while, EXDT decreases RGDP by 0.97%. In the fitted gaussian process regression, the main effect of INDT, EXDT, RINR, REXR and OPEN for predicting RGDP were 38.30%, 12.20%, 1.10%, 2.00%, and 1.20% respectively which were increased after the independent re-sampling to 56.30%, 6.90%, 3.10%, 2.80%, and 2.10% for predicting RGDP. The estimated performance of FMKL-GLD quantile model techniques revealed that FMKL-GLD 50Q model was efficient for examining and predicting economic growth in Nigeria. Thus, INDT, RINR, REXR and OPEN positive contribution to RGDP were 17.94%, 29.42%, 7.99% and 145.10% respectively. Meanwhile, RGDP, as a result of EXDT was reduced by 3.92%. Therefore, government and policymakers should properly harness the benefit of trade openness to engender international patronage for economic growth. Also, coupler FMKL-GLD 50Q quantile regression technique and gaussian process regression method are the most efficient predictive statistical methods to deal with multicollinearity and outliers. However, Nigeria’s economy had gone through various seasons, thus, a further study can be done to investigate structural breaks and propose appropriate model(s).