a SciTechnol journal Research Article Leo Daniel et al., J Plant Physiol Pathol 2013, 1:2 http://dx.doi.org/10.4172/jppp.1000105 Journal of Plant Physiology & Pathology All articles published in Journal of Plant Physiology & Pathology are the property of SciTechnol, and is protected by copyright laws. Copyright © 2013, SciTechnol, All Rights Reserved. International Publisher of Science, Technology and Medicine Effect of Polymeric Additives, Adjuvants, Surfactants on Survival, Stability and Plant Growth Promoting Ability of Liquid Bioinoculants Leo Daniel Amalraj E 1 *, Venkateswarlu B 1 , Suseelendra Desai 1 , Praveen Kumar G 1 , Mir Hassan Ahmed SK 1 , Meenakshi T 1 , Uzma Sultana 1 , Sravani Pinisetty 1 and Lakshmi Narasu M 2 Abstract The present study was conducted to evaluate the effect of polymeric additives, adjuvant and surfactants for their ability to support growth, shelf-life stability and bio-effcacy of liquid bioinoculants (Bacillus megaterium var. phosphaticum, Azospirilum brasilense and Azotobacter chrococcum). Liquid inoculants formulated with 2% polyvinylpyrollidone (PVP 30 K), 0.1% carboxy methylcellulose (CMC-high density) and 0.025% Polysorbate 20 promoted long-term survival of Bacillus megaterium var. phosphaticum, Azospirillum and Azotobacter with 5.6 x 10 7 , 1.9x10 8 and 3.5x10 7 cfu ml -1 , respectively after 480 days of formulation when stored at 30 o C. Maize seeds treated with consortium of PSB and Azospirillum brasilense enhanced plant growth positively by a multitude of synergistic mechanisms when compared to single inoculant application. Keywords Liquid inoculants; Cell protectants; Shelf life; Growth promotion Introduction Bioinoculants contain benefcial bacteria that enhances plant growth by the virtue of its nutrient solubilisation [1], nitrogen fxation [2], phytohormone production [3,4] and induction of defence mechanism [5-7] abilities. In India, Azospirillum, Azotobacter, Rhizobium, potash mobilizing bacteria, phosphate and zinc solubilising bacteria were included under Fertilizer control order, 1985 in view of nourishing the organic agriculture through the application of quality bioinoculants. Bhattacharyya and Kumar [8], stated that, bioinoculants manufactured in India are mostly solid carrier based and have a shelf life of only six months. Tese carrier- based inoculants are inherent with certain constraints like lower shelf-life, poor survival under adverse environmental conditions, high degree of contamination, and inconsistent feld performances. Tere have been many attempts to fnd alternatives for carrier based inoculants and, also to enhance viability of microorganisms in the inoculants. Besides, it requires a signifcant amount of processing, *Corresponding author: Leo Daniel Amalraj E, Division of Crops Sciences, Central Research Institute for Dryland Agriculture, Santoshnagar, Hyderabad, Andhra Pradesh, India-500059, E-mail: leodanielamalraj@hotmail.com Received: March 02, 2013 Accepted: Apirl 29, 2013 Published: May 03, 2013 such as mining, drying, milling, neutralizing and also becomes expensive in sterilization, formulation and transportation processes. Liquid inoculant formulations (LIF) could be a possible solution to the foresaid problems. It containing not only the desired microorganisms and their nutrients but also special cell protectants or additives that promote for longer shelf life and tolerance to adverse conditions [9]. Moreover, additives in the broth will improve inoculants quality, such as including better adhesion to seed [10], stabilizing the product, binding or inactivating soluble seed coat toxins. Many kinds of polymers have been used for inoculant production because of their ability to limit heat transfer, their good rheological properties and high water activities. Tese polymers, such as sodium alginate [11], gum Arabic [12], polyvinyl pyrrolidone (PVP) [13], polyvinyl alcohol (PVA) [14] and polyethylene glycol (PEG) [15] are normally used as adhesive when they are applied to seed. Polymers are also used to entrap bacteria in microbeads [16,17]. Tey are also soluble in water and make convenient for seed application a simple process for farmers. Te selection of ingredients was based on their properties, such as solubility in water, non-toxicity and complex chemical nature, which prevents microorganisms in the soil from rapidly degradation. It is always a herculean task for a single inoculant to instigate signifcant impact on the plant growth. Co-inoculation can beneft plant growth by diferent mechanisms [11]. Hence, we evaluated the optimum concentration of polymers, surfactants and adjuvants for LIF that could sustain the bacterial shelf life and also studied its bioefcacy in pot culture using maize (Zea mays. L) as test crop. Materials and Methods Microorganisms Bacillus megaterium var. phosphaticum (BMPSB 01), Azospirillum brasilense (ASP 20) and Azotobacter chrococcum (AZB 29) were taken from microbial culture bank, Central Research Institute for Dryland Agriculture, Hyderabad, India. Tey were isolated from rhizospheric soil of maize plants in Hayathnagar Research Farm, Hyderabad, India. Growth medium for liquid inoculants A modifed Pikovaskaya’s broth composed of (gL -1 ) yeast extract: 5.0, dextrose: 10.0, Ca 3 (PO 4 ) 2 : 5.0, KCl: 0.5, MgSO 4 : 0.2, MnSO 4 : 0.1, FeSO 4 : traces, (NH 4 ) 2 SO 4 : traces, glycerol: 10 ml was used to culture Bacillus megaterium var phosphaticum. Modifed Jenson’s broth was used to culture Azotobacter which composed of sucrose: 20, K 2 HPO 4 : 1.0, MgSO 4 : 0.5, Nacl: 0.5, FeSO 4 : 0.1, Na 2 MoO 4 : 0.005, glycerol: 10 ml and for Azospirillum, modifed nitrogen free bromothymol blue medium containing L-Malic acid: 5.0, K 2 HPO 4 : 0.5, MgSO 4 : 0.2, Nacl: 0.1, CaCl 2 : 0.02, Na 2 MoO 4 : 0.002, MnSO 4 : 0.01, FeEDTA (1.64% w/v): 4.0 ml, glycerol: 10 ml, bromo thymol blue (0.5% w/v in ethanol): 3.0 ml, KOH: 4.5, biotin: 0.1 were used as a basal media to evaluate the efect of additives on cell growth. Screening diferent concentration of additives on bacterial growth All the three media were amended with diferent concentrations of additives as follows: PVP at 1.0, 2.0, 3.0 and 5.0% (w/v); PEG at