Effect of Plant Growth Promoting Rhizobacteria (PGPR) and Cytokinins on the Growth and Yield of Wheat (Triticum aestivum L.) under drought

Abstract

Drought effects plant internal functions as the constraint for production. Different strategies are using to mitigate it. Plant growth promoting rhizobacteria (PGPR) and cytokinins (CK) plays important role under water stress and help to enhance crop growth. Seed inoculation with PGPR is increase soil fertility. Growth hormones like cytokinins improve plant functions and actual yield through exogenous application. To determine the effect of PGPR and cytokinins on the growth and yield of wheat under drought, planned wire house and field experiment were arranged at the research area of Agronomy Department, The Islamia University of Bahawalpur. Four wire house experiments and three field experiments were set, to check PGPR and CK effecr wheat growth and yield under drought. First wire house experiment was the screening of best genotype of wheat variety in drought. 10 different wheat varieties (V1= Aas-2011, V2= Mairaj-2008, V3= Fareed-2006, V4= Punjab-2011, V5= Lasani-2008, V6= Faisalabad-2008, V7= Galaxy2013, V8= Millat-2011, V9= AARI-2011, V10= Uqaab-2000) were used for screening under water deficit stress at tillering, anthesis and grain filling stage to identify best genotype under drought stress under agro ecological conditions of Bahawalpur. Galaxy2013 was observed the highest yielding variety under drought stress among them. It was also noticed that drought stress damaged crop functions and growth. Second experiment was to identify the best PGPR strain. Azospirillum, Bacillus, Rhizobium, Pseudomonas, Enterobacter and Moraxella were isolated from soil rhizosphere of Acacia nilotica under. A. brasilense Azo-1 was selected as a best PGPR strain among them. Next experiment was carried in both wire house and field entitled, “Cytokinins applied under drought stress to improve growth and physiological efficiency of wheat (Triticum aestivum L.)”. Seven treatments were used in experiment (To =Control, T1 =Drought at tillering, T2 =Drought at tillering + CKs Application, T3 =Drought at anthesis, T4 = Drought at anthesis + CKs Application, T5 = Drought at grain filling, T6 = Drought at grain filling + CKs Application). 5th experiment (wire house) was arranged to investigat the effect of Azospirillum brasilense and Rhizobium pisi on agronomic traits of wheat (Triticum aestivum L.) and results showed that co-inoculation gives the best results. 6th experiment was carried under field condition entitled, “Use of Azospirillum brasilense as a drought management tool in wheat crop” and noticed that A. brasilense inoculated wheat plants under drought showed more yield as compared to un-inoculated treatments. 7th, 2 years experiment was arranged to investigate the combine effect of PGPR and CK under drought stress in wheat crop. 13 treatments were used (To=Control, T1=Drought at tillering, T2=Drought at tillering +PGPR, T3=Drought at tillering +CKs, T4 = Drought at tillering +PGPR+CKs, T5 = Drought at anthesis, T6=Drought at anthesis +PGPR, T7=Drought at anthesis +CKs, T8=Drought at anthesis +PGPR+CKs, T9 = Drought at grain filling, T10 = Drought at grain filling +PGPR, T11 = Drought at grain filling+ CKs, T12 = Drought at grain filling +PGPR+CKs) in this experiment having three replications. Combined application of PGPR and CK is more beneficial for alleviation of drought. 5.90%, 3.49%, 4.09% and 6%, 8.51%, 4.07% more grain yield was recorded during 2016-17 and 2017-18 respectively, by combine application of PGPR and CK under drought. Beneficial bacteria colonize the rhizosphere impart drought tolerance. CK participate in removing of ROS from the cell and increases antioxidant enzymes during drought stress so plant growth and yield improved under such condition.