2.2.68
MOLECULAR VARIABILITY OF THE RICE LEAF SCALD PATHOGEN MONOGRAPHELLA ALBESCENS

HC TURNER

Natural Resources Institute, University of Greenwich, Chatham, Kent ME4 4TB, UK

Background and objectives
Rice leaf scald is a common disease of rice crops, occurring in nearly all of the rice-growing regions of the world. The causal organism, Monographelia albescens (Thorn) can pose a serious threat to rice production under favourable climatic and cultural conditions, particularly in upland areas. However, almost nothing is known about the variability of M. albescens

  • within or between populations [1]. We present here an analysis of the molecular variability of isolates collected from various regions of West Africa, Colombia and the Philippines, and discuss its implications.

    Materials and methods
    Samples of scald-infected rice leaves were provided by the West African Rice Development Association, the International Rice Research Institute and the Centro lnternationale de Agricultura Tropicale. DNA was extracted from successful isolations of the pathogen, and subjected to molecular analyses. Restriction fragment polymorphisms in the PCR-amplified ribosomal DNA (RDNA) region were analysed.

    Results and conclusions
    M. albescens showed remarkably little variability within the internal transcribed spacer (ITS) region of the RDNA. Of six restriction enzymes tested, only one revealed any variation, dividing the isolates into two groups. Greater variability was found in the intergenic spacer (IGS) region. Interestingly, cluster analysis again revealed two main groupings of the isolates, which showed a very close correlation with the groupings derived from the ITS region, suggesting a underlying biological reason for this grouping. The isolate groupings do not, however, correlate with geographical origin or host cultivar.

    This document is an output from projects funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of DFID.

    References
    1. Turner HC, Black R 1998. In: Sreenivasaprasad S, Johnson R, eds. Major Fungal Diseases of Rice. Dordrecht: Kluwer Academic Publishers, in press.