Symbitoic effectiveness of acid-tolerant rhizobia with common bean (Phaseolus vulgaris L.) in acid soil

• Main Authors: Ming-Yi Yen, 顏名沂
• Other Authors: 黃政華
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/30291223422901098247

碩士 === 國立中興大學 === 土壤環境科學系所 === 105 === Biological nitrogen fixation mediated by the legume-rhizobia symbioses is important for world agriculture. The yield of common bean (Phaseolus vulgaris L.) ranks second only to soybeans, and it is a common summer vegetable in Taiwan. Soil acidity is a limiting factor for legume growth because it affects the symbiotic efficiency of Rhizobium, host plant growth, and the legume production. Species of rhizobia vary significantly in their tolerance to low pH. Selecting acid-tolerant rhizobia may increase their symbiotic efficiency in acid soil. This study aimed to examine whether strains of Rhizobium spp. selected for growth on acid culture in vitro would also survive and grow better in acid soils. Sixteen Rhizobium spp. were isolated from commom bean nodules, and one commercial strain CIAT899 known for its acid-tolerance was included as a standard. Selective media with different pH levels (4, 5, and 6) and Al3+ concentrations (1, 2, and 3 mmol L-1) were used for selecting acid-tolerant rhizobia, and the nitrogen fixation and symbiotic efficiency of these rhizobia with common bean were evaluated in sandy medium with pH5. Four Rhizobium strains were selected for pot experiments including the acid- and Al3+-tolerant strain B412, acid-tolerant and Al3+-sensitive strain B379, acid-sensitive and Al3+-tolerant strain B378, and acid- and Al3+-sensitive strain B374. In addition, two soils with various Al3+ concentrations were used for pot experiments. B379 showed the highest nitrogenase activity in Renai soil with low Al3+ concentration (2.01 mg kg -1), but B378 resulted in the best nodule numbers in Tongxiao soil with is high Al3+ concentration (3.72 mg kg -1). However, B412 consistently showed a significant increase in bean yields in the two soils. Interestingly, the strain significantly increased the yield of bean by 50 % compared to that of the chemical fertilization treatment in Renai soil. Our study provides a strategy to select acid- and Al3+-tolerant rhizobia for increasing the yield of common bean grown in acid soils, increasing the nodulation and symbiotic effectiveness by Rhizobium. As a result, inoculation of common bean with acid-tolerant rhizobia may considerably reduce the use of chemical fertilizers for acid soils.