Co-inoculation of native multi-trait plant growth promoting rhizobacteria promotes plant growth and suppresses Alternaria blight disease in castor (Ricinus communis L.)

Sosanka Protim Sandilya; B Jeevan; Gangavarapu Subrahmanyam; Kironta Dutta; N Vijay; Nabanita Bhattacharyya; Mahananda Chutia

doi:10.1016/j.heliyon.2022.e11886

Co-inoculation of native multi-trait plant growth promoting rhizobacteria promotes plant growth and suppresses Alternaria blight disease in castor (Ricinus communis L.)

Heliyon. 2022 Nov 24;8(12):e11886. doi: 10.1016/j.heliyon.2022.e11886. eCollection 2022 Dec.

Authors

Sosanka Protim Sandilya^{1

2}, B Jeevan^{1

3}, Gangavarapu Subrahmanyam^{1

4}, Kironta Dutta¹, N Vijay¹, Nabanita Bhattacharyya⁵, Mahananda Chutia^{1

6}

Affiliations

¹ Central Muga Eri Research & Training Institute, Central Silk Board, Jorhat, 785700, Assam, India.
² Department of Microbiology, The Assam Kaziranga University, Jorhat, 785006, Assam, India.
³ ICAR- National Rice Research Institute, Cuttack, Odisha, 753006, India.
⁴ Seribiotech Research Laboratory, Central Silk Board, Kodathi, Bangalore, 560035, India.
⁵ Department of Botany, Gauhati University, Guwahati, 781014, India.
⁶ Muga Eri Silkworm Seed Organization, Central Silk Board, Guwahati, 781022, India.

Abstract

Background: Castor (Ricinus communis L.) is cultivated for seed oil and to feed (leaves) Eri silkworm, Samia ricini (Donovan) Hutt. Alternaria blight affects castor cultivation resulting substantial yield loss (∼30%). Uses of synthetic fertilizers and agrochemicals for disease management have serious concerns as the castor leaves are fed to eri silkworms for rearing. Application of plant growth promoting rhizobacteria for disease suppression and to enhance plant growth will be a healthier choice in castor cultivation. The aim of this study was to assess the efficacy of Alternaria blight disease suppression by native rhizobacteria isolated from wasteland castor and their ability on plant growth promotion.

Methodology: We isolated 50 bacterial antagonists from castor rhizosphere using the dilution plate method and evaluated their antagonistic activity against the castor blight pathogen, Alternaria ricini. Based on antimicrobial bioassay and plant growth promotion (PGP) traits (phosphate solubilization, ACC deaminase activities, production of IAA, GA₃, HCN, NH₃ and siderophore), salt and acid tolerance; we have chosen ten potential isolates and identified them through 16SrRNA gene sequencing and analysis. Disease suppression and plant growth studies were evaluated in pot experiments.

Results and conclusion: Three isolates namely, Enterobacter hormaechei (LRP-2), Bacillus mycoides (HF-1) and B. aryabhattai (UR-6) showed potential antagonistic activities and PGP traits which were selected for disease suppression and PGP studies. Application of PGPR consortia (LRP-2+HF-1) could suppress the plants from A. ricini infection in challenged inoculation. Mix inoculation of LRP-2 and UR-6 showed synergistic effect and enhanced plant growth in pot experiments. Combinations of E. hormaechei (LRP-2), B. mycoides (HF-1) and B. aryabhattai (UR-6) can be applied as bio-control and bio-fertilizer formulation to protect castor from Alternaria blight and also to enhance plant growth.

Keywords: Alternaria blight; Antagonists; Castor; Plant growth promoting rhizobacteria (PGPR); Wasteland.