Correlation between diversity of nitrogen-fixing bacterial community inhabiting the rhizoplane of acid sulfate soil-tolerant local paddy plant and rice production

在这项研究中，我们揭示了一个强大的能力，加里曼丹当地水稻品种种植在酸性硫酸盐土壤围场在南加里曼丹，印度尼西亚，这种水稻生产被认为是一个代表性的高产低投入的可持续农业。从当地水稻品种的根面，我们经常分离到鞘氨醇单胞菌属。从加里曼丹南部和中部地区的M.malabathricum根际和Xyris complanata根际中分离到的菌株为优势菌株。因此，许多鞘氨醇单胞菌属（Sphingomonasspp.）从当地水稻品种中分离到的10种根际细菌被认为是功能性根际细菌，1）有助于调节根际环境，2）直接固氮或至少调节根面条件使其更适合于固氮，以及3）由于加速微生物量积累而在根生物复合体的形成中起重要作用。因此，包括鞘氨醇单胞菌在内的根际微区系具有沿着分布于水稻品种根际的氮素吸收和根际环境缓冲能力，其强大的能力来源于其遗传多样性和稳定性。由于当地水稻茎和根的通气组织非常发达，因此有必要进一步研究其内部组织结构与内生固氮的关系。

In this study, we revealed a potent ability of Kalimantan local rice varieties cultivated on acid sulfate soil paddocks in South Kalimantan, Indonesia, and this rice production is regarded as a representative highly produced low-input sustainable agriculture. From the rhizoplane of local rice varieties, we have often isolated Sphingomonas spp. and a major strain was the same with those isolated from Melastoma malabathricum rhizoplane and Xyris complanata rhizosphere in South and Central Kalimantans. Thus, many Sphingomonas spp. isolated from the local rice varieties were considered to be functional rhizobacteria, 1) contributing to moderation of the rhizospherous environments, 2) directly fixing nitrogen or, at least, adjust the rhizoplane condition to be more suitable for nitrogen fixation, and 3) playing an important role in rhizo-biocomplex formation due to acceleration of microbial biomass accumulation. Therefore, rhizospherous microfloral communities including the Sphingomonas sp. established along the root system of local rice varieties are able to acquire nitrogen and buffer the rhizospherous environments, of which potent abilities are coming from their genetic diversity and stability. Since aerenchyma of the local paddy rice are remarkably developed well in the stems and roots, it is further necessary to study relationship between the inner tissue structures and endophytic nitrogen fixation.