Citricoccus zhacaiensis B-4 (MTCC 12119) a novel osmotolerant plant growth promoting actinobacterium enhances onion (Allium cepa L.) seed germination under osmotic stress conditions

Abstract

The water potential of rhizospheric soil is a key parameter that determines the availability of water, oxygen, and nutrients to plants and microbes. Recent global warming trends and erratic precipitation patterns have resulted in the emergence of drought as a major constraint of agricultural productivity. Though several strategies are being evaluated to address this issue, a novel approach is the utilization of microbes for alleviation of drought stress effects in crops. Citricoccus zhacaiensis B-4 is an osmotolerant actinobacterium isolated from banana rhizosphere on mannitol supplemented medium (-2.92 MPa osmotic potential). This isolate expressed plant growth promotion traits viz, IAA, GA3 production, phosphate, zinc solubilization, ACC deaminase activity and ammonia production under PEG induced osmotic stress and non-stress conditions. Under in vitro osmotic conditions, biopriming with the actinobacterium improved the percent germination, seedling vigour and germination rate of onion seeds (cv. Arka Kalyan) at osmotic potentials up to -0.8 MPa. Considering its novelty, osmotolerance and plant growth promoting traits, biopriming with C. zhacaiensis is suggested as a viable option for the promotion of onion seed germination under drought stressed environments.

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

“…Siddikee et al (2010) isolated several halotolerant actinobacteria strains with ACC deaminase, from the soil of barren fields and the rhizosphere of naturally growing halophytic plants and found that they can increase canola plant growth. Similarly, Selvakumar et al (2015) identified ACC deaminase producing Citricoccus zhacaiensis B-4, an osmotolerant actinobacterium from the banana rhizosphere and observed improved percent germination, seedling vigor and germination rate on onion seeds (cv. Arka Kalyan) at osmotic potentials up to -0.8 MPa.…”

Plant Growth-Promoting Rhizobacteria (PGPR): A Rampart against the Adverse Effects of Drought Stress

“…improved the germination rate and seedling vigor index of both tomato Arka Meghali and Pusa Ruby varieties under osmotic stress conditions compared to untreated seeds [178]. Inoculation of onion (Allium cepa L.) seeds under osmotic pressure conditions (-0.8 MPa) by an osmotolerant actinobacterium Citricoccus zhacaiensis B-4 resulted in an improved germination rate and seedling vigor [179]. The increase in germination rate of chickpea in the presence of two concentrations of PEG (15% and 30%) was proved through inoculation of P. putida (RA) in two varieties of chickpea compared with untreated seeds [176].…”

“…The use of PGPR can increase CK concentrations under water-limited conditions. Selvakumar et al [179] showed that inoculation of tomato plants with CK-producing bacteria Citricoccus zhacaiensis and B. amyloliquefaciens improved photosynthesis, transpiration, relative water content, and yield of plants during water stress.…”

Drought adaptive microbes as bioinoculants for the horticultural crops

“…The osmotolerant actinobacterium, Citricoccus zhacaiensis was reported for exhibiting ACC deaminase along with multitudinous growth enhancing traits including production of IAA, gibberellins and ammonia; solubilization of phosphorus and zinc. The inoculation of this strain in the onion seeds sown under drought stressed conditions were reported for improving the germination rate and seedling vigour ( Selvakumar et al., 2015 ). In an investigation, Citrobacter freundii , a drought tolerant and ACC deaminase producing rhizobacterium was reported alleviating the water deficit stress in tomato crop ( Ullah et al., 2016 ).…”