Correlation Study of Siderophore-Producing Bacteria Population in the Rhizo- and Endosphere of Rice Cultivated in Different Soils

• Main Authors: Thi-Thuy Phan, 潘氏水
• Other Authors: Li-Sen Young
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/43g2yb

碩士 === 國立虎尾科技大學 === 生物科技系碩士班 === 104 === The aim of this study is to understand the number and proportion of siderophore-producing bacteria (SPB) in relation to different rice genetic backgrounds and edaphic factors, as well as their effects on rice growth. Two rice Oryza sativa cvs., TK8 and TCN1, were cultivated in greenhouse condition using non-sterile acidic, near-neutral and red soils for 30 days. Total bacteria and SPB numbers were estimated from the bulk soils, rhizospheres, seed, root and shoot tissues of two rice cultivars. The percentage of SPB (SPB/total bacteria count x 100%) was highest in the near-neutral bulk soil at 5.47%, and relatively lower in acidic and red bulk soil at 3.58% and 0.27%, respectively. The percentage of SPB endophytes in TK8 seed (31.79%) was approximately ten-fold higher than in TCN1 seed (3.00%). The near-neutral rhizospheres showed the highest number of SPB in both rice varieties (1.4x102 CFU g−1 with TK8; 9.4x10 CFU g−1 with TCN1), and the lowest data was obtained from the red rhizospheres (1.1x10 CFU g−1 with TK8 and 1.5x10 CFU g−1 with TCN1). In all soil types and rice tissue types, the TK8 cultivar accommodated SPB endophytes higher than that of TCN1. By 16S rDNA sequence, a total of eight distinct bacterial endophytes exhibiting the strongest siderophore-producing activity were identified from various tissues of two rice varieties cultivated in three different soil-types. Bacteria belong to the genera Pantoea was predominant (n=4) and mostly isolated from seeds. Under sterile condition, rice seedlings inoculated with most SPBs formed a distinct orange halo on CAS medium significantly larger (from 14% to 28% with TK8, and from 13% to 34% with TCN1) than that in non-inoculated control. In the pot experiment performed with TCN1 and red soil, the inoculation of strain LS-756 showed significant increases in plant root length, shoot length and dry weight. In addition, inoculation of all strains (except LS-757) significantly enhanced chlorophyll a, chlorophyll b and total chlorophyll contents from 10% to 14%, 68% to 91% and 14% to 33%, respectively. The results proved that the number and proportion of SPBs associated with rice were influenced by host-genotype and edaphic factors. The knowledge gained from this study provided an important link about the role of SPB on rice iron uptake, the relationship with chlorophyll contents, and could further improve abiotic stress tolerances not only in rice, but also in other plants.