Transmission of Sarocladium oryzae (Sawada) W. Gams and Hawksw. through rice seed
1987
Milagrosa, S.P.
The occurrence of Sarocladium oryzae on nondiscolored seeds and hot-water treated seeds indicated that the organism can be present on symptomless seeds and is potentially important as seed-borne pathogen. The organism was growing inside rice hulls and on brown rice. S. oryzae survived in seeds for five months at 25-28 C, 20 C and 2 C. It decreased with longer time of storage and was replaced by storage fungi. Infection was also noticed at all stages of plant growth; as early as five days after sowing in untreated and hot-water treated seeds. This indicates that infection of S. oryzae occurs earlier than the reproductive stage, when obvious symptoms appeared. Injection of spore suspension resulted in leaf sheath browning two weeks after inoculation, however, both spraying and injection of inoculum gave the maximum disease incidence at maturity. In general, at early stages of plant growth there was less infection of S. oryzae on plants raised from hot-water treated seeds but as the plants approach maturity, infection between untreated and hot-water treated seeds did not differ. In a field experiment, sudden decrease of S. oryzae infection was probably due to senescence of the initially infected leaf sheath. The infection of the leaf sheath increased from seedling stage to maturity. More severe sheath rot infection on tillers of hot-water treated seeds than other treatments was observed. The fungus was observed from brown planthopper which was assayed by the signs of the disease on incubated excised leaf sheath. Infection of S. oryzae on leaf sheaths was greater on plants previously infested with brown planthopper than uninfested plants.
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