First report of rice blast (Magnaporthe Oryzae) on rice (Oryza Sativa) in Western Australia

You, M. P. and Lanoiselet, V. and Wang, C. P. and Shivas, R. G. and Li, Y. P. and Barbetti, M. J. (2012) First report of rice blast (Magnaporthe Oryzae) on rice (Oryza Sativa) in Western Australia. Plant Disease, 96 (8). pp. 1228-1229. ISSN 0191-2917

Abstract

Commercial rice crops (Oryza sativa L.) have been recently reintroduced to the Ord River Irrigation Area in northern Western Australia. In early August 2011, unusual leaf spot symptoms were observed by a local rice grower on rice cultivar Quest. A leaf spot symptom initially appeared as grey-green and/or water soaked with a darker green border and then expanded rapidly to several centimeters in length and became light tan in color with a distinct necrotic border. Isolations from typical leaf lesions were made onto water agar, subcultured onto potato dextrose agar, and maintained at 20°C. A representative culture was lodged in the Western Australian Culture Collection Herbarium, Department of Agriculture and Food Western Australia (WAC 13466) and as a herbarium specimen in the Plant Pathology Herbarium, Plant Biosecurity Science (BRIP 54721). Amplification of the internal transcribed spacer (ITS)1 and (ITS)2 regions flanking the 5.8S rRNA gene were carried out with universal primers ITS1 and ITS4 (4). The PCR products were sequenced and BLAST analyses used to compare sequences with those in GenBank. The sequence had 99% nucleotide identity with the corresponding sequence in GenBank for Magnaporthe oryzae B.C. Couch, the causal agent of rice blast, the most important fungal disease of rice worldwide (1). Additional sequencing with the primers Bt1a/Bt1b for the β-tubulin gene, primers ACT-512F/ACT-783R for the actin gene, and primers CAL-228F/CAL-737R for the calmodulin gene showed 100% identity in each case with M. oryzae sequences in GenBank, confirming molecular similarity with other reports, e.g., (1). The relevant sequence information for a representative isolate has been lodged in GenBank (GenBank Accession Nos. JQ911754 for (ITS) 1 and 2; JX014265 for β-tubulin; JX035809 for actin; and JX035808 for calmodulin). Isolates also showed morphological similarity with M. oryzae as described in other reports, e.g., (3). Spores of M. oryzae were produced on rice agar under “black light” at 21°C for 4 weeks. Under 30/28°C (day/night), 14/12 h (light/dark), rice cv. Quest was grown for 7 weeks, and inoculated by spraying a suspension 5 × 105 spores/ml onto foliage until runoff occurred. Inoculated plants were placed under a dark plastic covering for 72 h to maximize humidity levels around leaves, and subsequently maintained under >90% RH conditions. Typical symptoms of rice blast appeared within 14 days of inoculation and were as described above. Infection studies were successfully repeated and M. oryzae was readily reisolated from leaf lesions. No disease symptoms were observed nor was M. oryzae isolated from water-inoculated control rice plants. There have been previous records of rice blast in the Northern Territory (2) and Queensland, Australia (Australian Plant Pest Database), but this is the first report of M. oryzae in Western Australia, where it could potentially be destructive if conditions prove conducive.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 04 Jun 2017 21:54
Last Modified: 29 Nov 2017 00:31
Uncontrolled Keywords: plant science; plant pathology and symbioses; Plant Pathology; Fungi - cereal hosts;
Fields of Research : 06 Biological Sciences > 0607 Plant Biology > 060704 Plant Pathology
07 Agricultural and Veterinary Sciences > 0703 Crop and Pasture Production > 070308 Crop and Pasture Protection (Pests, Diseases and Weeds)
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970106 Expanding Knowledge in the Biological Sciences
B Economic Development > 82 Plant Production and Plant Primary Products > 8204 Summer Grains and Oilseeds > 820402 Rice
Identification Number or DOI: 10.1094/PDIS-05-12-0420-PDN
URI: http://eprints.usq.edu.au/id/eprint/31522

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