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Seed Germinability Tests for Predicting Field Emergence of Rice Seeds Infected with Helminthosporium oryzae and Trichoconis padwickii. Martin M. Kulik, Research Plant Pathologist, Seed Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; Phytopathology 67:1303-1304. Accepted for publication 1 April 1977. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1303.

Forty-eight lots of rice seeds were evaluated by the blotter health test for the amount of infection by Helminthosporium oryzae and Trichoconis padwickii. Germinability of these seed lots kept in towels in a germinator, in sand at two depths in the greenhouse, and in soil in a growth chamber, was determined at several temperatures. Twenty-six lots were sown in the field and seedling emergence was recorded. Infection of seeds by H. oryzae was closely correlated (r = 0.82**) with seedling emergence in the field. In contrast, infection by T. padwickii correlated poorly (r = 0.09) with field emergence. Highly significant correlation coefficients were obtained between field emergence and germinability in (i) towels at 15, 20, and 30 C, (ii) in the sand bench under 3 cm of sand and cool conditions, and (iii) in soil in a growth chamber at 20 C. Infection by H. oryzae was closely correlated (P = 0.01) with the results of these same three tests, with the exception of the towel test at 30 C. Thus, the towel test at 15 or 20 C can substitute for the blotter health test to predict the field emergence of H. oryzae-infected rice seeds. The correlation between H. oryzae infection and germinability in sand at 3 cm in a cool greenhouse was not so good as with the other tests. The soil test in a growth chamber at 20 C can predict field emergence of rice seeds, but it is not practical for routine work.