Characterization of rice sheath rot from Siniloan, Philippines

Abstract

We document here a rare incidence of rice sheath brown rot in the fourth crop of an upland rice successive cropping experiment (two crops year-1) planted in October 1999 using elite upland indica line IR55423-01 and lowland hybrids Mestizo and Magat (crop management details available from T. George). This crop grew normally until flowering, after which disease symptoms started to develop on all cultivars in January 2000. The plants showed dark brown lesions on flag-leaf sheaths, poor panicle emergence, spikelet sterility, and brownish black discolored seed. The symptoms resembled bacterial sheath brown rot caused by Pseudomonas fuscovaginae. We characterized the causal agent and performed a genotypic comparison of the isolates with a previous collection of sheath rot isolates from the Philippines (Cottyn et al 1996), P. fuscovaginae strains from Japan and Burundi (Duveiller et al 1988, Miyajima et al 1983), and other Pseudomonas strains related to the disease (Jaunet et al 1995) by BOX-PCR fingerprinting (see table).