Bacteria from the rhizobia group have been previously identified as grass-endophytes in grassland with cropping history of legumes. In this paper we aimed to demonstrate that strains of the Rhizobium genus, isolated from the rhizosphere of a rice Cuban cultivar subjected to intensive monoculture management, behave as endophytes and promote its growth. Eleven bacteria previously isolated from the rhizosphere of rice plants, were screened for their plant growth promoting traits. We found that some of them were able to solubilize inorganic phosphate compounds, produce siderophores and biofilm, have exocellulase and protease activity and were able to inhibit the phytopathogen Pyricularia oryzae growth. The phylogenetic analysis using partial sequences of 16S rRNA gene showed that bacteria isolated from rice plant of cultivar INCA LP-5 belonged to Rhizobium, Agrobacterium and Pseudomonas genera. Two strains analyzed, Rhizobium sp. Rpr2 and Rdp16, increased the height and biomass of rice plants, 70 days post-inoculation in greenhouse conditions. According to the quantification of Rhizobium sp. strain Rpd16 in surface-disinfected tissues of root and sheath, together with the analysis of confocal microscopy images, we can conclude that the Rdp16 strain is a rice endophyte of the cultivar INCA LP-5. This investigation is the first evidence of endophytic rhizobia able to promote the rice growth of a Cuban cultivar subjected to intensive monoculture, without rotation with legume plants and without a previous history of rhizobia inoculation.

来自根瘤菌组的细菌先前已被鉴定为具有豆科植物种植历史的草原中的草内生菌。在本文中，我们旨在证明从古巴水稻栽培品种的根际分离出来的根瘤菌属菌株，在单一栽培管理下具有内生菌的作用并促进其生长。筛选了先前从水稻植物根际分离的 11 种细菌，以确定它们的植物生长促进特性。我们发现其中一些能够溶解无机磷酸盐化合物，产生铁载体和生物膜，具有外切纤维素酶和蛋白酶活性，并且能够抑制植物病原体Pyricularia oryzae 的生长。16S rRNA部分序列的系统发育分析基因表明，从栽培种INCA LP-5的水稻植物中分离出的细菌属于根瘤菌属、农杆菌属和假单胞菌属。分析了两种菌株，根瘤菌属。在温室条件下接种 70 天后，Rpr2 和 Rdp16 增加了水稻植株的高度和生物量。根据根瘤菌的定量sp. 在根和鞘表面消毒的组织中发现菌株 Rpd16，结合共聚焦显微镜图像分析，我们可以得出结论，Rdp16 菌株是栽培品种 INCA LP-5 的水稻内生菌。这项调查是第一个证据表明内生根瘤菌能​​够促进古巴单一栽培品种的水稻生长，无需与豆科植物轮作，也没有根瘤菌接种史。