Disease Note.

Grain Discoloration of Rice Caused by Pseudomonas glumae in Latin America. R. S. Zeigler, Rice Program, Centro Internacional de Agricultura Tropical, CIAT, Apartado aéreo 6713, Cali, Colombia. E. Alvarez, Rice Program, Centro Internacional de Agricultura Tropical, CIAT, Apartado aéreo 6713, Cali, Colombia. Plant Dis. 73:368. Accepted for publication 2 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0368B.

Fluorescent Pseudomonas spp. (P. fuscovaginae Miyajima, Tani, & Akita and P. syringae pv. syringae Young et al) and nonfluorescent P. avenae Manns cause grain discoloration of rice (Oryza sativa L.) in Latin America and elsewhere. The only other Pseudomonas sp. (nonfluorescent P. glumae Kurita & Tabei) known to cause rice grain discoloration has not been reported outside Asia. Discolored rice grain collected from farmers' fields in Colombia and from seed received in routine international exchange of rice germ plasm from elsewhere in Latin America yielded nonfluorescent Pseudomonas spp. (1 × 1.5 µm, mUltiple polar flagella) that reproduced grain symptoms when emerging rice panicles were inoculated with bacterial suspension (10⁹ cfu/ml) at 100% RH, 24 hr. Strains were similar to P. avenae in that they were positive for catalase, nitrate reduction, growth at 41 C, and growth on citrate and acetate agar and negative for arginine dihydrolase, lipase, starch hydrolysis, H₂S production from TSI, levan formation from sucrose, indole, and utilization of sucrose. However, they differed from P. avenae by being negative for oxidase and positive for utilization of salicine, arginine, adonitol, and inositol. These differences indicate that the nonfluorescent strains are P. glumae rather than P. avenae. Both species could be eradicated from small seed samples with dry heat treatment of 65 C for 6 days.