Empowering rice seedling growth by endophytic Bradyrhizobium sp. SUTN 9‐2

Abstract

Bradyrhizobium sp. strain SUTN9‐2 was confirmed as rice endophytic bacteria and also as rice growth promotion agent. SUTN9‐2 showed the capability of plant growth promotion characteristics, such as indole‐3‐acetic acid (IAA) and 1‐amino‐cyclopropane‐1‐carboxylic acid (ACC) deaminase productions and nitrogen fixation. In this study, the ability of SUTN9‐2 to stimulate rice growth was investigated at different stages with N‐free and NH4NO3 under in vivo condition. The rice dry weight and chlorophyll content could be enhanced when SUTN9‐2 was inoculated in N‐free, especially at seedling stage (7 and 14 dai). The rice dry weight was also increased when SUTN9‐2 was inoculated with NH4NO3 at 7 and14 dai. The results of quantitative analysis of IAA and ACC deaminase were inconsistent with the expression of genes involved in IAA (nit) and ACC deaminase (acdS) productions. This inconsistently could implied that IAA and ACC deaminase produced from SUTN9‐2 do not directly affect rice growth, but other factors resulting from the production of IAA and ACC deaminase could be involved. Moreover, the expression of genes involved in nitrogen fixation (nifH and nifV) of SUTN9‐2 was also induced in rice tissues. This finding suggested that rice growth promotion may be supported by NH4NO3 together with nitrogen fixation by SUTN9‐2. Significance and Impact of the Study Indole‐3‐acetic acid, 1‐amino‐cyclopropane‐1‐carboxylic acid deaminase productions and nitrogen fixation may play important roles in rice growth promotion by endophytic SUTN9‐2, especially at early rice seedling growth stage, which has the potential to be used as rice seedling growth promoter in the system of rice intensification.

Microbial inoculants: reviewing the past, discussing the present and previewing an outstanding future for the use of beneficial bacteria in agriculture

“…(Baldani et al 2000; Tran et al 2000; Govindarajan et al 2007), Bradyrhizobium sp. (Greetatorn et al 2019).…”

Application of rice endophytic Bradyrhizobium strain SUTN9-2 containing modified ACC deaminase to rice cultivation under water deficit conditions

“…Bacteria-inoculated and uninoculated seedlings (three plants per test tube) were transferred and grown in a glass test tube (15 × 150 mm) as described by Greetatorn et al (2019). At 14 DAI, water stress was induced in the glass test tubes by replacing the Hoagland nutrient solution with a nutrient solution containing polyethylene glycol (PEG8000) (Santa Cruz Biotechnology, Inc., USA).…”

“…Recently, rice endophytic Bradyrhizobium sp. SUTN9-2 was used to investigate growth promotion in rice seedlings; SUTN9-2 (wild type strain) was used as a bio-inoculant to promote rice growth at the seedling stage (seven and 14 days after inoculation) in Nfree and with NH 4 NO 3 in vivo conditions (Greetatorn et al 2019). In addition, our previous study on SUTN9-2 showed it improved the ACC deaminase activity through enhancing the symbiotic interaction, plant biomass and drought tolerance in the mung bean (Sarapat et al 2020).…”

Distinct Root Microbial Communities in Nature Farming Rice Harbor Bacterial Strains With Plant Growth-Promoting Traits

“…Some of the genera that were more abundant when associated under unfertilized nature farming management play an important role in plant health and development. For example, Haliangium produces haliangicin as an antifungal compound that can inhibit the growth of a wide spectrum of fungi (Fudou et al, 2001), and Bradyrhizobum is known as PGPR and is able to fix atmospheric nitrogen (Greetatorn et al, 2019). A greater abundance of iron-reducing bacteria, including the Sideroxydans, Acidibacter and Anaeromyxobacter genera, was found under unfertilized nature farming conditions than under conventional farming conditions (Hori et al, 2010;Falagán and Johnson, 2014;Jin et al, 2017).…”