TRANSMISSION OF RICE DISEASES BY SEEDS AND PRINCIPLES FOR THEIR CONTROL: 1 -FUNGI ASSOCIATED WITH RICE SEED, AND SOME OBISERVATIONS ON SEED-BORNE INFECTIONS.

Document Type : Original Article

Authors

1 Plant Pathology Research Institute, Agricultural Research Centre, Giza, Egypt

2 Danish Government Institute of Seed Pathology, Hellerup, Copenhagen, Denmark

Abstract

Sixteen fungi developed on blotter from 118 rice seed samples of 6 cultivars. All tested seed samples yielded Drechslera oryzae, whereas 84 samples showed infection with Pyricularia oryzae. Seeds of "Reiho" cultivar were heavily infected with the blast fungus(65%), although "Giza 171 and Giza 172" showed increase in percentage of seed infee­tion in 1984 than usual. Seeds of cultivars IR 1626 and "IR 50" seem to be free from Fusarium moniliforme, F.semitectum, Nigrospora oryzae, P. oryzae and Trichoconiella padwickil,; however, they showed low seed infection with the brown spot fungus. Gerlachia oryzae, was observed in one sample of "Giza 171" at 0,50% which may be below the standard level of tolerance. The seed-borne fungi vary greatly according to the cultivar, locality and yearly variation of climatic conditions. Infection per­centages with D.oryzae increase when seed were incubated for 5-6 days , whereas seed infection with P.oryzae increased on the fourth day of in­cubation using water agar plate method. There was an indication of di­rect relation between seed infection and seed rot or seedling decay in case of both fungi, i.e.D. oryzae and P.oryzae. Five fungi viz. D. oryzae, F. moniliforme, F. semitectum, P.oryzae and T. padwickii were detected in pericarp and endosperm of rice seed. P.oryzae was also observed in the embryo.

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