Semester of Graduation

Summer 2019

Document Type



Sheath blight (ShB), caused by Rhizoctonia solani Kühn, is an economically important soil-borne disease of rice (Oryza sativa) that can cause up to 50 % yield losses. Application of fungicides is the most effective and commonly used method for managing sheath blight. However, the pathogen can develop new resistant strains upon continuous exposure to a fungicide. Moreover, the use of inorganic fungicides is not eco-friendly. The utilization biological control agents (BCAs) can be a more sustainable and safe means of managing ShB. To develop alternate strategies for ShB management, I am exploring the effect of the silicon (Si) fertilization in reducing sheath blight disease in combination with BCAs. Bacteria were isolated from the rhizosphere of healthy rice plants and screened by dual-culture for their antifungal activity against R. solani. Among 534 isolates 24 antagonists were identified to Bacillus spp based on their 16S rDNA sequence. Two isolates were of were evaluated for their synergistic activity with silicon against ShB in a greenhouse setting. The combined application of silica and BCAs reduced the development of ShB in rice plants compared to non-treated control and plants that received a single treatment suggesting that simultaneous use of the two materials could effectively manage ShB. I also evaluated the effects of R. solani inoculation and BCAs application on the bacterial communities of rice rhizosphere in the field at the LSU AgCenter H. Rouse Caffey Rice Research Station. The genomic DNAs of the microbial communities of the rice rhizosphere of Si-treated and non-Si-treated plants were extracted. The 16S rDNA regions of the extracted DNA were amplified and sequenced. The beta diversity analysis performed with Qiime2 revealed that the microbiome profile of rhizosphere of the inoculated plants was significantly different from non-inoculated ones. Although silica application reduced development, it did not affect much the microbial profile on the rice rhizosphere.

Committee Chair

Ham Jong Hyun

Available for download on Monday, June 22, 2020