Diversity of nifH gene pools in the rhizosphere soil of rice plant after long-term fertilizer application

• Main Authors: Horng-I Chu, 朱宏怡
• Other Authors: 譚鎮中
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/58550497243891852771

博士 === 國立中興大學 === 土壤環境科學系所 === 98 === Long-term fertilizer application are known to cause changes in soil physical, chemical properties and microbial population. Biological nitrogen fixation is an important process by soil microorganisms, not only to help plant growth but also maintain the balance of natural nitrogen cycle. Rice is the most important food crop in the world, including Taiwan. Many of nitrogen-fixing bacteria associated with rice rhizosphere by the accumulation of root exudates have been selected and published, but research about nitrogen-fixing bacteria on the rhizosphere under different fertilization management is rare. The purpose of this study was to test the hypothesis that in paddy soil, nitrogen-fixing bacterium population would be changed considerably after a long-term fertilizer application. Unculturable methods was used to study the composition of the nifH gene in rice rhizosphere at different growth stages after long-term (ten years) chemical fertilizer and swine manure compost application, and the potential factors influencing the population was proposed. The results showed that nitrogen-fixing activities of rice rhizosphere under different fertilizer managements were not significant different, but there were significant changes under different growth stages. Restriction enzyme fragment length polymorphism analysis (RFLP) also showed different nifH gene profiles at different growth stages, but not significantly different among fertilization treatments. Cloning technique was thus used to sequence the nifH gene, The results indicated growth stage, significant change of the rhizospheric nifH pool under long-term applications of fertilizers. Several nifH genes disappeared in some fertilization treatments. nifH gene compositions at different growth stages were similar in different fertilization treatments but varied in from dominancy. Although RFLP method could not distinguish the nifH gene profiles under the different fertilizations, cloned nifH gene sequence revealed significantly different among fertilization treatments. These results support the hypothesis that the nitrogen fixing bacterium population changed considerably after long-term fertilizer application. The study also established the first nifH gene database in Taiwan paddy soil, and found that there are a large number of newly discovered nifH gene unknown.