Abstract
Spikelets of rice plants at flowering were most susceptible to invasion of Pseudomonas glumae. When P. glumae invaded into flowering spikelets at a density of 1cfu/grain or more, the population of bacteria in spikelets greatly increased up to 9 days after the flowering day, resulting in bacterial grain rot of rice. In rice spikelets the time of accumulation of intermediate sugars for the biosynthesis of grain starch were consistent with the time of increase of bacterial population. P. glumae was able to utilize intermediate sugars except for sucrose and triose phosphates. Oxolinic acid (5-ethyl-5, 8-dihydro-8-oxo[1, 3]dioxolo[4, 5-g]quinoline-7-carboxylic acid, Starner®) had an antibacterial activity against P. glumae on the epidermis of spikelets, and reduced the bacterial infectivity into rice spikelets. Oxolinic acid applied to flowering spikelets also inhibited multiplication of P. glumae invaded into spikelets and protected grains from bacterial grain rot of rice.
