Rice seedbeds as a source of primary infection by Rice yellow mottle virus

The effect of contamination of rice seedlings by Rice yellow mottle virus (RYMV) in seedbeds on the onset and spread of rice yellow mottle in the field was investigated. Rice seedlings were artificially contaminated in seedbeds at different rates (0.1, 0.5, and 2.5%) and pooled in bundles before transplantation, as done by farmers. RYMV was successfully transmitted through contaminated hands and bundling healthy and diseased seedlings together. Hand contamination was responsible for 4.5% infection. Disease incidence in the field after secondary spread reached 32% for 2.5% seedbed contamination rate but remained limited (less than 10%) for all other rates. Eradicating infected plants from seedbeds lessened disease incidence in the field. This technique may be used in conjunction with other prophylactic measures to efficiently control rice yellow mottle disease.