一條根 (闊葉大豆 Glycine tomentella) 之根瘤菌分離及特性研究

Abstract

Nitrogen is abundant and an important element in agricultural production. However, profusely applying chemical nitrogen fertilizer may not enhance the absorbability efficiency of plants (only about 50 % efficiency), but leads to waste and tremendous impact on the environment. Broadleaf soybean (Glycine tomentella) is called “I-Tiao-Gung” in local name in Chinese. Now Kinmen County Agricultural Research Institute actively promotes the local farmers to plant “I-Tiao-Gung” as commercial crop, nevertheless, once the applied fertilizer washed away, it would directly affect the marine ecology. Symbiosis of legumes and Rhizobium would form nodule to convert atmospheric nitrogen into ammonia (NH3), which plants could use directly. This study selected the most suitable Rhizobium from different soils that was able to be symbiotic with “I-Tiao-Gung” and analyze the type and characteristics of isolated Rhizobium. For overcoming the problem regarding germination rate, soaking the seeds of “I-Tiao-Gung” into condensed sulfuric acid for 10 minutes could increase the germination rate to 80 %. “I-Tiao-Gung” was planted in three soils, the one that could develop nodule with Rhizobium were screened and purified. In three soils, there were 30 strains were isolated and three of them grew faster among all 30 strains. After preliminary inoculation test, a total of 12 strains had successful nodule. The results of 16S rDNA identification indicated they were Bradyrhizobium elkanii, Bradyrhizobium iriomotense, Bradyrhizobium iaoningense, and Rhizobium multihospitium, respectively, which gave a total of 4 species and 2 genera. Four strains identified were tested to compare the population number and the ability of symbiotic nodulation under different pH. Results showed that at pH 6.8 would give the best population and nodule number. To examine the ability of symbiotic nodulation in soil environment, “I-Tiao-Gung” were inoculated with four strains in three soils. Among four inoculated strains, Br. iriomotense had the best nodule quantity and the highest nitrogenase activity. However, high available nitrogen would inhibited ability of nodulation and nitrogen fixation activity.