Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/1996
Publication Date: N/A
Technical Abstract: Panicle blight (PB) is a disorder of rice which causes reduced seed production on the seed head and has been observed for many years in the USDA-ARS breeding nursery located in Beaumont, TX. The cause is unknown but symptoms have been associated with weather patterns and genetic backgrounds. In 1995, severe PB symptoms were observed throughout the breeding nursery, as well as, in commercial fields across the Texas Gulf Coast and was associated with reduced yield and milling quality. In addition to this impact, we were interested in determining if PB symptoms would affect seed germination and seedling vigor. Rough rice samples of 8 cultivars which had been grown in 4 different production years were obtained from cold storage. The 1995 samples came from a study where up to 65% PB was observed in some cultivars. Rough rice samples were separated into 4 weight fractions using a fractionating aspirator. The proportion of the total sample that was in the heaviest and lightest fractions was determined. Fifty of the best kernels from these 2 fractions were evaluated for germination. Seed sources from 1995 had lower grain weight, greater contamination by weak pathogens, a greater proportion of light kernels, and lower germination of the heaviest (best) kernels. Studies were also conducted to determine if seed treatment would improve quality of seed lots having high levels of PB. Treatment with a surface sterilant or fungicide improved seed germination and seedling vigor of PB seed lots but not to the level of seed lots having low PB. Seed treatment appears to reduce the influence of the weak pathogens but does not override the negative impact of PB per se on seed quality. Factors which pre-dispose a plant to PB symptoms appear also to subject the seed to colonization by weak pathogens.