Effect of dihydrostreptomycin spray upon the grain development and carbohydrate content of rice

Abstract

Spraying with dihydrostreptomycin (Dsm) has been reported to be effective for control of bacterial leaf blight of rice, incited by Xanthomonas oryzae, but occasionally causes reduction of the grain yield. The present experiment showed that, two or three times applications of Dsm to rice plant, including spray at the stage of flowering, caused reduction in the percentage of grains of standard weight, but not in the number of panicles per plant nor number of spikelets per panicle. It was also indicated that Dsmspray at the flowering stage did not effect fertilization, but caused reduction in average grain weight, suggesting a retarding effect on the ripening process of rice grains. Quantitative analysis was made for sugar and starch in the selected organs of rice plant, sprayed with Dsm (1000ppm) at the flowering stage. It was revealed that contents of total sugar, reducing sugar, and starch in the flag leaf of rice plant sprayed, were equal to those of check. Sugar and starch contents in the sheath and culm of plant subjected to spray with Dsm were greater than those of check. In the grains, however, sugar content of the sprayed plant was much greater, and starch was considerably less, than that of check. Accordingly, the difference in sugar content between flag leaf and grain of Dsm-sprayed plant was considerably small as compared with that of checkplant. It is suggested that Dsm-spray may give an inhibitory effect to translocation of sugar from flag leaf to grain and starch accumulation in grain of rice plant.