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Ridzuan, Nur Izzati (2022) Biological control of basal stem rot disease in mature oil palm (Elaeis guineensis) in inland and peat soil. PhD thesis, University of Nottingham.

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Abstract

Oil palm is the main commodity crop cultivated in Malaysia and has made significant contributions to the economies of Malaysia and Indonesia. However, there is a major problem in oil palm, the basal stem rot (BSR) disease caused by Ganoderma boninense. This is a serious threat to the oil palm industry as it reduces oil palm yield and shortens the economic lifespan of the crop. In order to control this disease, this present study evaluated the efficacy of Trichoderma spp. as a biological control agent (BCA) through the application of different types of bioorganic fertilizers at selected oil palm estates in Palong, Pahang and Tanjung Karang, Selangor with different palm ages and soil types.



Trichoderma spp. was produced on large scale through the submerged fermentation method. Conidial seed culture resulted in higher Trichoderma spp. count from the bioreactor (6.32 log cfu/ml) in comparison to mycelial seed culture (4.95 log cfu/ml) and this was statistically significant (P<0.001). Trichoderma spp. was then mixed with biochar as the carrier at different ratios; 1:0.5 (B50%), 1:1 (B100%) and 1:2 (B200%) for ease of handling and long term storage. For oil palm field applications, Trichoderma-biochar (T-biochar) formulations were added into organic fertilizer, Living Organic Fertilizer (LOF) as the final products at concentrations of 0% (T1/T6), 5% (T2/T7), 10% (T3/T8) and 20% (T4/T9). The viability of Trichoderma spp. in the carrier and biofertilizer was monitored for up to 24 weeks. It was found that B100% was the best formulation for biochar with Trichoderma populations between 5.00-6.00 log cfu/g while there was no significant difference for the Trichoderma spp. count in biofertilizers at 10% (T3/T8) and 20% (T4/T9) formulations (around 5.00 log cfu/g).

In the oil palm plantations, the treatments were divided into two bioorganic fertilizer treatments, 1) Fortified Living Organic Fertilizer (FLOF) with customised N, P and K formulations; Treatments T1 to T5 and 2) LOF; Treatments T6 to T10 with different percentages of Trichoderma spp. (0, 5, 10 and 20%). Populations of microorganisms including bacterial, fungal and Trichoderma spp. were monitored for up to 24 months. Even though Trichoderma spp. count fluctuated over time and between treatments (between 4.00-5.00 log cfu/g), there was a significant difference in treatment T9 (20% Trichoderma in LOF) as it had the highest Trichoderma spp. populations at both Palong and Tg Karang plantations. Total bacterial and fungal populations were not significantly different (P≥0.05) at both locations. The soil pH at both locations was acidic whereas the electrical conductivity (EC) in Palong was low, below 0.10 dS/m. Nutrient analyses on soil and leaf samples revealed that the nitrogen, phosphorus and potassium (N, P and K) levels were correlated with the fertilization regime at both estates. Generally, the disease incidence (DI) for BSR disease at Palong was low (below 13.0%) and can only be noticed in few treatments (T1 to T6) with T1 (FLOF control) showed an increment in DI at 20 and 24 months (12.5%). In comparison, at Tg Karang, high DI was recorded for all the treatments especially T8 (10% Trichoderma in LOF) and T10 (Grower’s standard practice; GSP) with DI of 29.2% and 25.0% respectively at 24 months. Palong plantation also recorded a low percentage of palms with the disease at 5.2% and 3.5% for control and Trichoderma treatments respectively whereas the percentage increased between 3-6 folds at Tg Karang. Additionally, while no recovery was recorded for control palms, seven palms from the present Trichoderma treatments were found to have completely recovered from BSR disease (two and five palms at Palong and Tg Karang respectively).

Subsequently, Trichoderma spp. and other fungal communities in the rhizospheres of healthy, asymptomatic and symptomatic palms were identified through Sanger sequencing method. This is the first study that reported and evaluated the structure of fungal communities in oil palm rhizospheres over the course of BSR disease. Trichoderma spp. were present in rhizosphere soils at Palong and Tg Karang but with different distributions across the different symptoms. However, only healthy palms retained unique Trichoderma spp. T. asperellum was detected between all the symptoms which indicates that this species might be indigenous to the soil or from residual bioorganic fertilizer applications. Analysis of the fungal-ITS (internal transcribed spacer) DNA region revealed that healthy palms at Palong were similar to each other with 8 common genera. Asymptomatic and symptomatic palms had four and one common genera respectively. In contrast, the fungal communities were distinct across all samples at Tg Karang and ectomycorrhizal fungi (ECM) was absent in asymptomatic and symptomatic palms. Regardless of soil types, it was observed that Ascomycota was the dominant phyla in healthy and asymptomatic palmss. Conversely, symptomatic palms were dominated by Basidiomycetes which suggested a shift in the fungal community. Furthermore, ITS DNA of Trichoderma spp. and Ganoderma spp. in the palm rhizospheres was quantified via quantitative real-time Polymerase Chain Reaction (qPCR). The quantity of Trichoderma and Ganoderma DNA was not significant between the different symptoms, but Ganoderma DNA was detected ten-fold higher in symptomatic palms. Comparison between the Palong and Tg Karang plots showed that the quantity of Ganoderma at Tg Karang was also ten times higher than at Palong. For Trichoderma, the quantity was similar at Palong and Tg Karang which was between 0.020-0.035 ng/µl.

Overall, this research revealed that Trichoderma spp. had biocontrol activity in mature oil palm estates infected with Ganoderma spp., but the effects were influenced by biotic and abiotic factors. Such impacts on Trichoderma populations should be studied further. This study also provides evidence on the changes of the fungal communities in oil palm rhizosphere soils with regards to BSR disease. Further evaluation needs to be conducted to elucidate the role of other fungal communities that could co-exist with Trichoderma as a biological control agent for the control of BSR disease in oil palm.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Supramaniam, Christina Vimala Goh, Kar Mun
Keywords:	trichoderma spp., basal stem rot (BSR), field study, oil palm, biological control agent, rhizosphere, fungal communities
Subjects:	S Agriculture > SB Plant culture
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Science > School of Biosciences
Item ID:	69395
Depositing User:	Ridzuan, Nur Izzati
Date Deposited:	24 Jul 2022 04:40
Last Modified:	23 Jul 2024 04:30
URI:	https://eprints.nottingham.ac.uk/id/eprint/69395

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