Organisms causing rice seed discoloration and their possible effect on germinability
1990
Misra, J.K. | Jergon, E.B. | Mew, T.W. (International Rice Research Inst., Los Banos, Laguna (Philippines). Seed Health Unit)
Discoloration, whether caused by microorganisms or some other factors, does have significant influence on the health of the seeds, particularly on their germinability. Discolored seeds exhibit fungal and bacterial infestations than the normal looking ones, when subjected to standard blotter test using alternating cycles of 12 hours of darkness and NUV light. The most common organisms encountered with the discolored seeds collected during the 1988 wet season were Sarocladium oryzae, Curvularia sp., Alternaria padwickii, bacteria, Phoma spp., Fusarium moniliforme, Fusarium spp., Verticillium Cinnabarinum, Higespora oryzae, and F. semitectum in their descending order of occurrence, which ranged between 5 and 46%. To assess the effect of seed discoloration on germinability, a standard germination test for 10 seed lots belonging to different varieties, viz., IR36, IR64, IR66, R1000, C1000, 661 and IAC25 was carried out. The result showed that germination percentage of normal seed lots was higher (87-99.5%) than that of discolored ones (66.75-98%). There was no significant variation in germinability of the normal seed lots whereas among the discolored ones, 4 seed lots (varieties IAC25, 661, IR36 and IR66) varied significantly at the 5% level of probability. The result indicates that seed discoloration may significantly affect the germination capability of rice. The possibility of the discolored seeds of other varieties to show similar trend toward the suppression of germinability cannot be ruled out.
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