FUNGI SEED-BORNE IN RICE (ORYZA-SATIVA) IN SRI-LANKA

Fungi of the following 26 genera were found to be seed-borne in rice in Sri Lanka: Acrocylindrium, Alternaria, Aspergillus, Cephalosporium, Cercospora, Chaetomium, Cladosporium, Curvularia, Drechslera, Epicoccum, Fusarium, Macrophomina, Magnaporthe, Myrothecium, Nigrospora, Phoma, Phomopsis, Pyrenochaeta, Rhizopus, Sordaria, Stemphylium, Trichoconis, Trichoderma, Trichothecium and Verticillium. The most important pathogens were Drechslera oryzae and Trichoconis padwickii. Although non-viable spores of Pyricularia oryzae were found in some seed samples, the fungus was never isolated in a viable form. Fungi were detected in seed samples from all the agro-ecological regions of the country sampled. However, there were differences in the extent of seed infection in different locations, seasons and cultivars. 'Seed spotting' was a symptom widely prevalent, the fungi commonly associated with this condition being species of Curvularia and to a lesser extent, D. oryzae, T. padwickii and Fusarium spp. None of these seed-borne fungi caused serious effects in the new improved cultivars when crops were raised from well-filled mature seed which had been harvested and processed under favourable conditions. The results of this study indicate that the new improved cultivars extensively cultivated in Sri Lanka are not adversely affected by endogenous seed-borne fungi. In particular, they have adequate resistance to indigenous races of the blast fungus, P. oryzae but, as numerous races of this pathogen occur elsewhere, every precaution must be taken to ensure that virulent races are excluded.