SUSCEPTIBILITY OF RICE SPIKELETS TO INFECTION WITH PSEUDOMONAS-GLUMAEAND ITS POPULATION-DYNAMICS

Spikelets of rice plants at flowering were most susceptible to invasio n of Pseudomonas glumae. When P. glumae invaded into flowering spikele ts at a density of 1 cfu/grain or more, the population of bacteria in spikelets greatly increased up to 9 days after the flowering day, resu lting in bacterial grain rot of rice. In rice spikelets the time of ac cumulation 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 dro-8-oxo[1,3]dioxolo[4,5-g]quinolin e-7-carboxylic acid, Starner(R) had an antibacterial activity against P. glumae on the epiderimis of spikelets, and reduced the bacterial in fectivity into rice spikelets. Oxolinic acid applied to flowering spik elets also inhibited multiplication of P. glumae invaded into spikelet s and protected grains from bacterial grain rot of rice.