Identification and pathogenicity of Pantoea spp. in leaf blight disease of Oryza sativa l. located at IADA Barat Laut Selangor / Muhammad Nazri Ishak

Muhammad Nazri , Ishak (2022) Identification and pathogenicity of Pantoea spp. in leaf blight disease of Oryza sativa l. located at IADA Barat Laut Selangor / Muhammad Nazri Ishak. Masters thesis, Universiti Malaya.

	PDF (The Candidate's Agreement) Restricted to Repository staff only Download (193Kb)
	PDF (Thesis M.A) Download (2385Kb)

Abstract

Leaf blight is one of the major constraints to rice production and this disease is commonly associated with bacterial species Xanthomonas oryzae pv. oryzae (Xoo). However, in recent years, bacteria belonging to the genus Pantoea had also been reported to cause leaf blight disease in rice-growing areas worldwide. The objectives of this study were to determine leaf blight disease infestation in rice fields using aerial monitoring, to identify leaf blight disease-causing agent in IADA Barat Laut Selangor rice fields, and to evaluate the pathogenicity of the leaf blight disease-causing agent on locally cultivated rice. A series of surveys were conducted in several localities in IADA Barat Laut Selangor rice fields from October to December 2018 using unmanned aerial vehicle (UAV) to monitor and identify areas with leaf blight disease infestation. Symptomatic leaves from the areas were collected, surface-sterilised and subjected to bacterial isolation on Trypticase soy agar (TSA) medium. The morphological characteristics of the isolates were determined. The isolates were then purified for biochemical assays including Gram-testing, catalase, oxidase, KOH, starch hydrolysis, and anaerobic tests. The isolates were subjected to a preliminary pathogenicity test against local rice cultivar, MR220 using clipping method. The isolates showing leaf blight disease symptoms were further analysed for molecular identification using 16SrRNA markers. The identified causing agents were confirmed with a second pathogenicity test against another local rice cultivar, MR220CL2. Aerial monitoring of rice fields identified 15 plots infested with leaf blight disease. The infestation coverage ranged from 6.6 to 48.2%. The isolates from the field yielded mild, yellow-pigmented colonies with undulated margin, raised elevation, and circular to irregular forms. The biochemical tests of the isolates displayed inconclusive determination of putative causative agents for leaf blight disease. The preliminary pathogenicity test showed five isolates displayed symptoms of leaf blight disease. Molecular analysis identified SK09 and SK15 isolates as Pantoea agglomerans and P. wallisii, respectively. The second pathogenicity test confirmed these two putative agents to cause leaf blight disease to cultivated rice, MR220CL2 similar to Xanthomonas oryzae pv. oryzae (Xoo). This study proposes the usage of UAV as one of the monitoring tools in rice fields especially for the application of disease surveillance in rice granaries. This study also identified Pantoea agglomerans and Pantoea wallisii as new causative agents for new leaf blight disease for rice in Malaysia. An understanding of this newly emerged pathogen should lead to guidelines for rice breeders and agricultural practitioners for developing sustainable management strategies for dealing with outbreaks of this disease in the future.

Actions (For repository staff only : Login required)