Biofertilizer and Biostimulant Potential of Pigeonpea (Cajanus scarabaeoides L.) Bacterial Endophytes In vitro and in Planta Study

Abstract

Endophytes are microorganisms that establish intimate, non-pathogenic associations with host plants, were isolated from wild pigeonpea. The study aimed to determine their potential as biofertilizers and biostimulants for enhancing the cultivated pigeonpea variety ICP 8863 growth. The experiment was laid out in completely randomized design with three replications at the Department of Plant Pathology, UAS, Bangalore, between January 2023 and February 2024. Endophytic bacteria were isolated from leaf and stem tissues of Cajanus scarabaeoides. These isolates were subjected to a qualitative screening assay to evaluate their potential for biofertilization, assessing phosphate, potassium, and zinc solubilization, siderophore production, and atmospheric nitrogen fixation. In planta experiments were conducted to determine the biostimulatory effects of these endophytes on plant growth. High-performance liquid chromatography (HPLC) was employed to profile phytohormone production by a selected, effective endophyte. Subsequent molecular characterization was performed for taxonomic identification. Twenty-five bacterial endophytes were isolated from wild pigeonpea, with nine displaying biofertilization potential. In planta evaluation identified SB3 as the most effective, significantly improving germination (91.11%), plant height (83.21 cm), branching (15.66), leaf production (49.66), and dry matter accumulation (139.84 g/plant). SB3 was shown to produce indole acetic acid, cytokinin, gibberellic acid, and abscisic acid via HPLC, and was identified as Bacillus subtilis through 16S rRNA sequencing. This study reveals the potential of wild pigeonpea endophytes as a bioresource for sustainable agriculture due to their ability to enhance plant growth through nutrient solubilization and phytohormone production, making them ideal for eco-friendly biofertilizers and biostimulants.