Mechanism of root growth and promotion of nodulation in vegetable soybean byAzospirillum Brasilense

Abstract

Stimulation of root growth and promotion of nodulation in vegetable soybean (Glycine max ) by Azospirillum brasilense was studied under lightroom conditions to understand the possible mechanism of root growth as well as the enhancement of nodule initiation when co-inoculated with Bradyrhizobium. Root growth stimulation of vegetable soybean was positively influenced by the cell-free supernatant of Azospirillum brasilense Sp7 as well as Sp7 itself, and by indole acetic acid (IAA) application. The cell-free supernatant of Sp7 treated plants produced the highest number of roots and root length plant 21 followed by bacterial cells of Sp7 2177 ORDER REPRINTS and IAA log 10 9 M) application. Control plants were the lowest. The cell-free supernatant of Sp7 may contain growth stimulants similar to IAA, which was responsible for enhanced root growth. Nitrite and nitrate did not show positive role in increasing root growth in vegetable soybean. Co-inoculation of Azospirillum with Bradyrhizobium significantly ðP , 0:05Þ promoted nodulation in vegetable soybean. Bradyrhizobium strain UPMR48 performed superior role on promotion of nodule growth by co-inoculation to the strain TAL102. Azospirillum has the potential as a coinoculant with Bradyrhizobium in vegetable soybean cultivation.

Legume Crops, Importance and Use of Bacterial Inoculation to Increase Production

“…cells (Burdman et al, 1996;Dardanelli et al, 2008, Volpin et al, 1996 induce the synthesis of flavonoids by roots of chickpea, common bean and alfalfa, in experiment of co-inoculation with rhizobia. Interestingly, it is not strictly necessary the presence of the bacteria, the application of bacteria-free exudates of symbiotic enhancers to the root exert similar effect that during bacterial-co-inoculation (Molla et al, 2001b). For example, the application of NFs analogues produced by Serratia proteamaculans 1-102 promotes soybeanbradyrhizobia nodulation and soybean growth (Bai et al, 2002b).…”

Potential of Rhizosphere Bacteria for Improving Rhizobium-Legume Symbiosis

“…Phytohormones and vitamins have also been coupled with the positive outcome of combined inoculation of legumes with Azospirillum plus Rhizobium (Plazinski and Rolfe 1985 ;. Growth of various legumes have been improved as a result of combined inoculation with Azospirillum and Rhizobium via enhanced production of plant hormones such as indole-3-acetic acid, gibberellic acid, and zeatin claimed as a mechanism for enhancement in rhizobial infection, nodule formation, and N 2 fi xation activity (Hungria and Vargas 2000 ;Molla et al 2001b ;Dardanelli et al 2008 ;Cassan et al 2009 ). In addition to plant hormone, the production of siderophores has also been reported when Azospirillum was used in combination with Rhizobium and stimulated legumes growth (Khan et al 2002 ;Wani et al 2007b ).…”

Co-Inoculation on Vegetative Growth and Soybean Seedlings Nodulation Subjected to Liming, Nitrogen Fertilization and Application of Micronutrients

“…Em condições laboratoriais, Molla et al (2001) analisaram o potencial de melhoria de crescimento das raízes e nodulação em soja co-inoculada com Azospirillum e Bradyrhizobium, sendo verificado que Azospirillum tem potencial para estimular significativamente o crescimento radicular até mesmo em plantas com raízes cortadas, o que implica em influência positiva sobre o crescimento e desenvolvimento radicular. Ainda, esses mesmos autores concluíram que Azospirillum não apenas influencia o crescimento radicular, mas também pode melhorar a iniciação e o desenvolvimento de nódulos em plantas de soja por co-inoculação com Bradyrhizobium.…”