Promotion of tomato (Lycopersicon esculentum Mill.) plant growth by rhizosphere competent 1-aminocyclopropane-1-carboxylic acid deaminase-producing streptomycete actinomycetes

Abstract

The ability of streptomycete actinomycetes to promote growth of tomato through the production of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase was evaluated under gnotobiotic and greenhouse conditions. To achieve this, 64 isolates of Streptomyces spp. obtained from a tomato rhizosphere in the United Arab Emirates were initially selected for their ability to produce ACC deaminase as well as indole-3-acetic acid (IAA) and subsequently for their rhizosphere competence as root colonizers. Of the two selected ACC deaminase-producing isolates showing exceptional rhizosphere competence, S. filipinensis no. 15 produced both ACC deaminase and IAA, whilst S. atrovirens no. 26 did not produce IAA. Under greenhouse conditions, the application of S. filipinensis no. 15 or S. atrovirens no. 26 resulted in the reduction of the endogenous levels of ACC, the immediate precursor of ethylene, in both roots and shoots and increased plant growth. Plant growth promotion was most pronounced in the presence of S. filipinensis no. 15 compared to S. atrovirens no. 26. This relative superiority in performance shows the advantage conferred to S. filipinensis no. 15 due to its ability to produce both IAA and ACC deaminase. In comparison, an ACC deaminase-producing isolate of S. albovinaceus no. 41 which was neither rhizosphere-competent nor capable of producing IAA, failed to promote plant growth compared to S. filipinensis no. 15 or S. atrovirens no. 26 although the growth promotion obtained by S. albovinaceus no. 41 was significant compared to control. The application of S. globosus no. 8, which was not rhizospherecompetent and did not produce detectable levels of ACC deaminase or IAA did not promote plant growth. These results indicate the importance of rhizosphere competence. In conclusion I report the production of ACC deaminase by streptomycete actinomycetes and its ability to enhance plant growth through reduction in the in planta levels of endogenous ACC and the consequent lowering of endogenous ethylene levels in plant tissues.

Plant growth-promoting actinobacteria: a new strategy for enhancing sustainable production and protection of grain legumes

“…Arka Kalyan) at osmotic potentials up to -0.8 MPa. El-Tarabily (2008) showed that ACC deaminase producing Streptomyces filipinensis 15 and S. atrovirens 26 could reduce tomato endogenous ACC levels in both roots and shoots, resulting in increased plant growth. Similarly, Palaniyandi et al (2013) also showed that some Streptomyces spp.…”

Plant growth promotion by streptomycetes: ecophysiology, mechanisms and applications

“…The application of Streptomyces filipinensis no. 15, a 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and IAA producer, reduced the endogenous levels of ACC, the immediate precursor of ethylene, in both roots and shoots and subsequently enhanced plant fitness to the environment [128]. Plant growth-promoting and stress-alleviating activities have been demonstrated for a halo-tolerant and ACC deaminase-producing Streptomycete sp.…”

Evaluation ofStreptomycesspp. for their plant-growth-promotion traits in rice

“…The efficacy of Streptomyces strains for PGP is extensively reported (Nassar et al 2003;El-Tarabily 2008;Gopalakrishnan et al 2012a, b). The soil biological activities and mineral nutrients (including microbial biomass carbon and nitrogen, dehydrogenase, total N, available P and % organic carbon) in the Streptomyces-treated rice plots, at harvest, were also found significantly higher over the untreated control plots.…”

“…Streptomyces are a group of Gram-positive bacteria, with high G + C content belonging to the order Actinomycetales, which form branched mycelia and hence sometimes been classified as fungi imperfecti. Plant growth promotion potential of Streptomyces was reported on bean (Nassar et al 2003), tomato (El-Tarabily 2008), pea (Tokala et al 2002), wheat (Sadeghi et al 2012) and rice (Gopalakrishnan et al 2012a, b). Streptomyces promote plant growth either by producing indole-3-acetic acid (Aldesuquy et al 1998) or siderophores (Tokala et al 2002).…”