• Login
• Admin

Khoo, Chee Chang (2025) The impact of Trichoderma spp. treatment on physical and biochemical properties of oil palm (Elaeis guineensis Jacq.), and associated soil fungal biodiversity under challenge with Ganoderma boninense. PhD thesis, University of Nottingham Malaysia.

PDF (Thesis - as examined) - Repository staff only until 7 February 2027. Subsequently available to Repository staff only - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Available under Licence Creative Commons Attribution. Download (2MB)

Abstract

Oil palm (Elaeis guineensis Jacq.) is a crucial crop in Malaysia, significantly contributing to the economy and global food supply. However, it is threatened by basal stem rot (BSR) disease caused by Ganoderma boninense without early infection symptoms, leading to reduced yields and premature palm death. This study aimed to evaluate the efficacy of Trichoderma spp. formulations in supporting plant growth and suppressing BSR disease under semi-controlled conditions. Additionally, it explored fungal biodiversity in the oil palm rhizospheric soil and identified potential early detection approaches for BSR through changes in fungal community composition.

The experiment was conducted with two categories of oil palm ramets: T1-T4 (non-inoculated) and T5-T8 (BSR-inoculated). The treatments were as follows: T1, T5 (no treatment/control); T2, T6 (Trichoderma spp. and biochar mixture, Tmix); T3, T7 (living organic fertilizer, LOF); T4, T8 (Tmix- and LOF-treated). LOF is nutrient-rich, containing high organic matter that enhances soil fertility and supports plant growth. Tmix promotes plant growth and suppresses BSR disease, with biochar serving as a carrier for Trichoderma spp. The ramets were inoculated with Ganoderma boninense using rubber wood blocks (RWBs) pre-colonized by the fungus while Trichoderma spp. were lab-cultured and mixed with biochar.

Post-infection analyses were only conducted at two time points, first and fourth months after planting, due to COVID-19 movement control order from March 2020 to November 2021. The analyses included the plant's physical properties (plant height, weight, stem diameter, leaf length, chlorophyll content/SPAD value, root length and weight), plants' disease severity index (DSI), soil chemical properties (pH and electrical conductivity, EC) and microbial counts. T1 ramets demonstrated the best growth and lowest DSI, likely due to minimal treatment stress, enabling better acclimatization and high survival rates. Among other treatments, T2 (non-inoculated, Tmix-treated) also had low DSI and the highest survival rate, highlighting the potential of Trichoderma spp. as a growth promoter. Conversely, T5 performed the worst in growth parameters and highest DSI (79.8%), emphasizing the severity of BSR disease in non-Tmix diseased plants.

Spectrophotometric enzyme assay for plant lignin biosynthesis enzymes (LBE: cinnamate 4-hydroxylase [C4H] and cinnamyl alcohol dehydrogenase [CAD]) and plant cell wall degrading enzymes (CWDE: chitinase and glucanase), along with lignothioglycolic acid (LTGA) assay, were conducted to evaluate enzyme activities and lignin content. Across treatments except T7, LBE activities increased from first month to the fourth month, especially in Tmix-treated plants. T4 showed the largest increment in CAD activity, while T2 recorded the highest CAD activity, 6.43 ODmin⁻¹mg⁻¹ and second-highest C4H activity, 5.80 ODmin⁻¹mg⁻¹, correlating with increased LTGA content. CWDE activities rose significantly in disease-inoculated plants (T5 to T8), with T6 and T8 (both Tmix-treated) showing the greatest increases. By the fourth month, chitinase activity in all diseased treatments exceeded 2.5 ODmin-1mg-1, with T6 and T8 reaching 2.78 and 2.71 ODmin-1mg-1 respectively. Glucanase activity followed a similar trend, with T8 having the highest activity, 6.14 ODmin-1mg-1 and followed by T6, 4.59 ODmin-1mg-1, while T5 and T7 exhibited smaller increases. Real-time polymerase chain reaction (qPCR) analysis revealed high Ganoderma spp. DNA in untreated diseased plants (T5, T7), but significantly reduced in Tmix-treated diseased plants (T6, T8), where Trichoderma spp. DNA remained high. These findings suggested Trichoderma spp. enhance LBE and CWDE enzyme activites as part of plant defences while suppressing Ganoderma spp. through direct antagonism and plant-mediated responses.

Subsequently, the fungal biodiversity of oil palm ramets' rhizospheric soil was analysed using next-generation sequencing and Microbiome Analyst tool. Four treatments were selected for analysis and relabelled for clarity: T1 (healthy control, HC); T2 (healthy treated, HT); T5 (diseased, D); T6 (diseased treated/recovering, R). HT exhibited the highest number of amplicon sequence variants (284 ASVs) and genus count (113 genera), whereas D had only 112 ASVs and 46 genera. Besides, the beta diversity plot showed the fungal cluster of D group distinctly located from the other groups, indicating high dissimilarity in fungal genera compared to others. Relative abundance comparisons of Trichoderma spp. and Ganoderma spp. revealed that naturally occurring Trichoderma spp. exhibited high relative abundance in HC without Tmix-treated but decreased in D, which was found lower than the relative abundance of Ganoderma spp. In R samples, the relative abundance of Trichoderma spp. increased following Tmix treatment, suppressing Ganoderma spp. These findings suggested that high relative abundance of naturally occurring Trichoderma spp. correlates with reduced disease incidence, while lower relative abundance increases risk of disease outbreaks. This insight offers a potential early detection strategy for BSR disease by monitoring fungal biodiversity, similar to a "health check" for plants and soil.

In conclusion, although assessing plant physical properties and biochemical interactions among ramets, BSR disease, and biocontrol agents is not novel, this study provided valuable insights into these interactions under semi-controlled conditions. It explored biochemical interactions by examining activities of LBE and CWDE. Moreover, it highlighted the soil fungal biodiversity associated with different plant health statuses, paving the way for identifying beneficial fungal clusters that promote plant growth, improve soil health, and suppress pathogens. This study could be the first to explore soil fungal biodiversity in oil palm rhizospheric soil concerning BSR disease under semi-controlled conditions. The findings suggested that Trichoderma spp. could potentially serve as a disease bioindicator for early BSR detection, as a decline in the relative abundance of naturally occurring Trichoderma spp. signals the onset of BSR disease. Future research could optimise Tmix application in infected plants to minimise the impact on microbial diversity. Additionally, validating the fungal community composition associated with different plant health statuses using field samples would enhance the applicability of these findings.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Chin, Chiew Foan Massawe, Festo Supramaniam, Christina Vimala
Keywords:	Elaeis guineensis Jacq.; basal stem rot (BSR); Trichoderma spp.; soil fungal biodiversity; semi-controlled conditions
Subjects:	S Agriculture > SB Plant culture
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Science > School of Biosciences
Item ID:	80318
Depositing User:	Khoo, Chee Chang
Date Deposited:	08 Feb 2025 04:40
Last Modified:	08 Feb 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/80318

Actions (Archive Staff Only)

Edit View