Photosynthetic bacterium Rhodopseudomonas palustris GJ‐22 induces systemic resistance against viruses

Abstract

SummaryPhotosynthetic bacteria (PSB) have been extensively used in agriculture to promote plant growth and to improve crop quality. Their potential application in plant disease management, however, is largely overlooked. In this study, the PSB strain Rhodopseudomonas palustris GJ‐22 was investigated for its ability to induce resistance against a plant virus while promoting plant growth. In the field, a foliar spray of GJ‐22 suspension protected tobacco plants against tobacco mosaic virus (TMV). Under axenic conditions, GJ‐22 colonized the plant phyllosphere and induced resistance against TMV. Additionally, GJ‐22 produced two phytohormones, indole‐3‐acetic acid and 5‐aminolevulinic acid, which promote growth and germination in tobacco. Furthermore, GJ‐22‐inoculated plants elevated their immune response under subsequent TMV infection. This research may give rise to a novel biological agent with a dual function in disease management while promoting plant growth.

Characterization of Rhodopseudomonas palustris population dynamics on tobacco phyllosphere and induction of plant resistance to Tobacco mosaic virus

“…The size expansion of strain GJ-22 colonies at the Phase IV stage suggested a better nutrient condition during this phase. Strain GJ-22 was reported to produce IAA as a signal to promote plant growth (Su et al, 2017). This phytohormone was also reported to induce release of nutrients, including saccharides, from plant cells (Spaepen et al, 2007;Limtong and Koowadjanakul, 2012).…”

“…The TMV-inoculated leaves were harvested at 6 days post-TMV inoculation and analysed for TMV accumulation by enzyme-linked immunosorbent assay (ELISA). To determine the expressions of defence-related genes, the TMV-inoculated leaves were harvested at 18 h post-TMV inoculation and the expressions of defence-related protein genes NbPR1a and NbPR3 were analysed by semi-quantitative reverse transcription-polymerase chain reaction (RT-qPCR) as described previously (Su et al, 2017).…”

“…In our previous report, we have shown that R. palustris GJ-22 strain can induce a systemic resistance (referred to induced systemic resistance [ISR] thereafter) to Tobacco mosaic virus (TMV) infection in tobacco and promote plant growth through production of two phytohormones (i.e. indole-3-acetic acid and 5-aminolevulinic acid; Su et al, 2017).…”

Characterization ofRhodopseudomonas palustrispopulation dynamics on tobacco phyllosphere and induction of plant resistance toTobacco mosaic virusinfection

“…R. palustris strain GJ-22 was from a previously reported source (Su et al, 2017) and routinely cultivated aerobically at 30 °C in a photosynthetic medium (PM) under a 6,500 lux lamination. The solid PM medium contains 0.1 g (NH 4 ) 2 SO 4 , 0.02 g MgSO 4 , 0.5 g Na 2 CO 3 , 0.05 g K 2 HPO 4 , 0.02 g NaCl, 0.2 g Casamino Acids, 0.15 g yeast extract and 18g agarose in one litre distilled water, pH 6.5-7.0.…”

“…Its potentials in organic farming are new topics of many research laboratories (Fawzy et al, 2012; Wong et al, 2014; Wu et al, 2013). In our previous report, we have shown that R. palustris GJ-22 strain can induce a systemic resistance (referred to induced systemic resistance [ISR] thereafter) to Tobacco mosaic virus (TMV) infection in tobacco and promote plant growth through productions of two phytohormones (i.e., indole-3-acetic acid and 5-aminolevulinic acid) (Su et al, 2017). Unlike many other PGPR strains that colonize plant rhizosphere, R. palustris GJ-22 can colonize plant phyllosphere and establish different sized colonies to exert beneficial effects to plant.…”