Evaluation of ACC deaminase producing Pseudomonas fluorescens strains for their effects on seed germination and early growth of wheat under salt stress

Abstract

Plant growth-promoting rhizobacteria possessing ACC deaminase activity reduces the level of stress ethylene, conferring resistance and improving plant growth under different stress conditions. The present study aims at evaluating Pseudomonas fluorescens strains for their potential to produce ACC deaminase and quantifying their effects on seed germination and seedling growth of wheat under salinity stress. Bacteria were first evaluated for their ability to utilize ACC, an immediate precursor of stress ethylene, using DF minimal medium containing 3 mM ACC and it was revealed that they were all able to use ACC as sole nitrogen source under in vitro conditions. Thereafter, the influence of bacterial strains on seed germination and seedling growth of wheat varieties was evaluated under NaCl induced salt stress after seven days. The experimental design was completely randomized in 3×5×5 factorial scheme with three replications. Factors consisted of salinity (0, 3 and 6 dS/m), P. fluorescens bacteria (strains PGU2-79, WBO-3, WKZ1-93 and WB1-7 and sterile water as control), and wheat variety (Chamran, Kooh-Dasht, Dehdasht, Karim and Jam). Twenty wheat seeds were transferred to plates after being soaked for an hour in bacterial suspensions at concentration of 10 8 CFU/ml. Each plate contained a filter paper which was moistened with 10 ml of NaCl solution in different concentrations. Plates were incubated in a growth chamber with maximum and minimum temperatures maintained at 20°C and 15 °C, respectively, with 12 h day-night photoperiod and relative humidity of 80%. Results revealed that P. fluorescens strains had positive impacts on different growth parameters of wheat varieties including germination percentage and rate, seed vigor, length and dry weight of coleoptile and radicle and salinity tolerance index of plants under salinity stress as compared to control. This study reveals the efficacy of plant growth promoting P. fluorescens strains containing ACC deaminase for improving salt tolerance and consequently stimulating the growth of wheat seedlings under salinity stress.

ACC Deaminase Producing Bacteria With Multifarious Plant Growth Promoting Traits Alleviates Salinity Stress in French Bean (Phaseolus vulgaris) Plants

“…The ethylene is a significant plant hormone required for every aspect of plant development and growth cycle but it stimulates, growth repressive effects, such as retardation of root development, inhibition of seed germination, promotion of aging, senescence and abscission process in plants under stressed conditions (Gupta and Pandey, 2019). Several reports suggested that application of ACC deaminase producers mitigate the adverse effect of salt stress manifested on plants by minimizing the ethylene emission to its optimum level and thus confers growth promotion and stress tolerance in stressed plants (Orhan, 2016; Maxton et al, 2018; Safari et al, 2018). The growth of French bean plants when subjected to salinity stress might be attributed to the ACC deaminase activity (>20 nmol α-ketobutyrate mg protein -1 h -1 ) of two selected strains, which declines the production of stress generated ethylene by deaminating its precursors, ACC into ammonia and α-ketobutyrate (Penrose and Glick, 2003).…”

Ethylene: A Master Regulator of Salinity Stress Tolerance in Plants

“…Ectopic expression of a homolog of AtERF38 (GhERF38 from G. hirsutum) in Arabidopsis resulted in ABA sensitivity in transgenic lines; therefore, reduced seed germination under salinity and drought stress was observed in the transgenic plants as compared to WT [101]. Plant growth-promoting Pseudomonas fluorescens strains improve salinity tolerance of plants due to its ability to produce ACC deaminase and, consequently, to stimulate seed germination in wheat under salinity stress [102]. With the higher activity of ACC deaminase, the Enterobacter cloacae HSNJ4 strain could effectively promote seed germination and could provide the salinity tolerance by degrading ACC, thus inhibiting ethylene synthesis [103].…”

Rhizobacteriome: Promising Candidate for Conferring Drought Tolerance in Crops

“…Pseudomonas fluorescens, Enterobacter hormaechei, and Pseudomonas migulae are three ACC and EPS producing microbes which when inoculated in foxtail millet could promote seedling germination in drought condition 75 . PGPR possessing ACC deaminase activity reduce toxicity of heavy metals, drought stress and other abiotic stresses like extreme temperature, salinity and soil pH, besides, antagonism against phytopathogens 76 73 . Leclercia adecarboxylata and Agrobacterium fabrum, Bacillus amyloliquifaciens with higher ACC-deaminase and IAA production traits elevated nutrients uptake and high chlorophyll contents 78,79 .…”