First Report of Leaf Blight of Rice Caused by Pantoea ananatis and Pantoea dispersa in Malaysia

Abstract

HomePlant DiseaseVol. 103, No. 7First Report of Leaf Blight of Rice Caused by Pantoea ananatis and Pantoea dispersa in Malaysia PreviousNext DISEASE NOTESFirst Report of Leaf Blight of Rice Caused by Pantoea ananatis and Pantoea dispersa in MalaysiaW. K. Toh, P. C. Loh, and H. L. WongW. K. TohFaculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, MalaysiaSearch for more papers by this author, P. C. LohFaculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, MalaysiaSearch for more papers by this author, and H. L. Wong†Corresponding author: H. L. Wong; E-mail Address: hlwong@utar.edu.myhttp://orcid.org/0000-0001-8903-1812Faculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, MalaysiaSearch for more papers by this authorAffiliationsAuthors and Affiliations W. K. Toh P. C. Loh H. L. Wong † Faculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, Malaysia Published Online:16 May 2019https://doi.org/10.1094/PDIS-12-18-2299-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In September to December 2016, the most severe leaf blight disease outbreak in the last 30 years occurred in the paddy field of Sekinchan, Selangor, Malaysia, causing 50 to 70% loss of the crop yield. During this outbreak, the newly introduced rice cultivar MR 284 suffered the most damage. Infected rice leaf blades showed brownish stripes, which subsequently turned pale and dry. Symptomatic leaves from the MR 284 plants were cut into 1-cm2 pieces, surface sterilized, and plated on peptone sucrose agar (Poulin et al. 2014). Yellowish bacterial colonies that were obtained after incubation at 28°C for 2 days were purified by streaking on nutrient agar. Identification of six randomly chosen bacterial isolates was performed using the BioMérieux Vitek 2 microbial identification system, which classified the isolates as Pantoea spp. with 93 to 96% identity probabilities. Subsequently, 16S rRNA gene amplification was performed using the universal primers 27F and 1492R. BLASTn analysis of the partial 16S rRNA gene sequences from the six isolates revealed that the sequences (1,421 bp) from two isolates, designated as PA strains, were identical to those of Pantoea ananatis (GenBank accession no. CP028033.1), and the sequences (1,435 bp) of four isolates, designated as PC strains, were identical to those of Pantoea dispersa (GenBank accession no. AB273743.1). The partial 16S rRNA gene sequences of PA and PC strains were deposited at GenBank under accession numbers MK578186 and MK263020, respectively. Pathogenicity assays of PA and PC strains were conducted on 60-day-old rice plants of cultivar MR 284 using the clipping method (Kauffman et al. 1973). The bacterial strains were cultured overnight on nutrient broth, and the inocula were adjusted to 108 cells/ml. Three fully extended leaves from the second and third tillers of each plant were inoculated by cutting at 3 to 4 cm from the leaf tip. Control plants were mock inoculated with sterile saline solution. The experiment was performed in duplicate. From 3 to 14 days after bacterial inoculation, the inoculated leaves showed progressive necrosis with color change from pale green, brown, and pale, whereas the control plants remained symptomless. Bacterial colonies were reisolated from inoculated leaves, producing colonies that were morphologically identical to those of PA and PC strains. The identities of these bacterial isolates were further verified to be the inocula PA and PC strains by 16S rRNA gene sequencing, thus fulfilling the Koch’s postulates. Previous reports had established Pantoea spp. as rice pathogens (Kini et al. 2017; Lee et al. 2010; Mondal et al. 2011). To our knowledge, this is the first report of rice leaf blight caused by P. ananatis and P. dispersa in Malaysia. The isolation of these pathogens allows newly developed cultivars to be more adequately tested before these cultivars are introduced to the farmers for mass cultivation.The author(s) declare no conflict of interest.