Variation of microbial communities in relation to plant species, bio-fertilizer application and plant density on slope soils / Lee Zi Ying

• Main Author: Lee , Zi Ying
• Format: Thesis
• Published: 2019
• Subjects: Q Science (General); QR Microbiology
• Online Access: http://studentsrepo.um.edu.my/15145/1/Lee_Zi_Ying.pdf; http://studentsrepo.um.edu.my/15145/2/Lee_Zi_Ying.pdf; http://studentsrepo.um.edu.my/15145/

Malaysia's cut slopes are prone to soil erosion and landslides especially when experiencing high precipitation, ranging from 2000 mm to 2500 mm per annum. One of the main contributors to soil erosion is the absence of strong plant root systems which stabilizes the soil structure. Slope plants strongly affect local environmental conditions, yet little is known about its effect on soil microbial diversity. The variation of bacterial and fungal communities in response to plant species, plant densities and bio-fertilizer application on six plots of slope soils were investigated using culture-dependent and culture-independent approaches. The first objective of the study was to isolate and identify culturable fungal and filamentous actinobacterial strains through selective isolation. The second objective was to investigate the bacterial and fungal diversity of plant rhizospheric and slope soils based on denaturing gradient gel electrophoresis (DGGE) analysis. The final objective was compare the variation of microbial communities in relation to two different flowering shrubs, two types of plant densities and bio-fertilizer application through diversity indices analysis. Results showed fungal communities among the different treatments plots consisting of fungal genera: Aspergillus, Chaetomium, Penicillium, Talaromyces and Trichoderma, and actinobacterial communities were dominated by Streptomyces species. There were 33 and 13 species of cultivable fungal and actinobacterial strains, respectively that were isolated from the planted plot soil samples. PCR-DGGE analysis of the fungal community revealed a high diversity of fungal taxa associated with high plant density. The results showed significant differences (P < 0.05) between densely and less densely planted plots but no significant difference between plant species and bio-fertilizer application which indicated that fungal community changes are significantly influenced by plant density instead of plant species and bio-fertilizer application. Results also showed that in general, the soil actinobacterial community diversity was more sensitive to plant related parameters than the bacterial community diversity. Actinobacterial community diversity was significantly influenced (P < 0.05) by plant species, followed by plant density whereas bacterial community diversity was more highly influenced by application of bio-fertilizer compared to plant density and plant species. Besides plant species, plant densities or bio-fertilizer factor effects to the microbial diversity, the interaction between experimental factors also affected the microbial community diversity. Results revealed that there were interactions among plant species, density and bio-fertilizer application on actinobacterial diversity; while, interactions were only found between plant density and bio-fertilizer treatment on bacterial diversity and there were no significant interaction on fungal diversity. In conclusion, the study revealed that microbial communities were strongly influenced by plant density, followed by bio-fertilizer application and plant species factor.