Journal article
Effects and possible causes of an unprecedented rice blast epidemic on the traditional farming system of Bhutan



Publication Details
Authors:
Thinlay, X.; Finckh, M.; Bordeos, A.; Zeigler, R.
Publisher:
ELSEVIER SCIENCE BV
Publication year:
2000
Journal:
Agriculture, Ecosystems and Environment
Pages range:
237-248
Volume number:
78
Start page:
237
End page:
248
Number of pages:
12
ISSN:
0167-8809

Abstract
In 1995, an unprecedented rice blast epidemic (caused by Pyricularia grisea) occurred in Bhutan in mostly traditional cultivars in the high (1800-2600 m) and some parts of mid altitude (1200-1800 m) agroecological zones. Possible causes of the outbreak such as introduction of a new pathogen race, unusual weather patterns and changes in agricultural practices were investigated and yield losses analysed. Weather data were examined for unusual patterns and farmers from the affected areas were interviewed to determine possible changes of cultural practices. Blast isolates were collected from various affected rice areas and analysed for variability of the pathogen population by MGR (Magnaporthe grisea repeat 586) fingerprinting. Rice yields declined parabolically with increasing disease with losses for some farmers being nearly 100%. Restriction fragment length polymorphism analysis using MGR fingerprints of 71 isolates resulted in 58 haplotypes that grouped into 13 lineages. Lineage BhR1 and BhR4, were represented by 22 and 13 isolates, respectively, whereas the other lineages were represented by only one to six isolates each. Haplotypic diversity both in the early and late season's collections was very high suggesting that the blast epidemic was not caused by a new introduction or race change of the pathogen. There was no drastic shift in agricultural practices or rice cultivars which could explain the blast outbreak. However, the weather data indicated that the climatic conditions in 1995 favoured blast and these unusual conditions, in combination with the ubiquitous presence of the pathogen, probably account for the epidemic. (C)2000 Elsevier Science B.V. All rights reserved.


Keywords
Bhutan, Magnaporthe grisea, MGR-fingerprinting, Oryza sativa, Pyricularia grisea, traditional farming system, yield losses


Authors/Editors

Last updated on 2019-01-11 at 16:03