rice microbial grain discoloration Causal agent: species of Sarocladium, Bipolaris, Alternaria, Gerlachia, Fusarium, Phoma, Curvularia, Trichoconiella and Pseudomonas etc. Gd (related) TO:0000023 Symptoms: darkening of glumes of spikelets, brown color to black including rotten glumes caused by one or more pathogens. Intensity ranges from sporadic discoloration to discoloration of the whole glume. Severity of grain discoloration can be estimated by counting of grains with more than 25% of glume surface affected. grain discoloration (related) plant_trait_ontology microbial disease response