Thermotolerant and halotolerant Streptomyces sp. isolated from Ajuga parviflora having biocontrol activity against Pseudomonas syringae and Xanthomonas campestris acts as a sustainable bioadditive in growth promotion of Cicerarietinum

Abstract

Beneficial rhizobacteria are important determinants of plant health and productivity. They influence nutrient uptake, stress tolerance, disease resistance, biodiversity etc. We have isolated bacterial isolate Streptomyces sp. (AB-11) from rhizospheric soil of an important medicinal plant Ajuga parviflora, displaying growth promoting attributes like production of siderophores, indole acetic acid, phosphate solubilization, calcite solubilization, nitrogen fixation etc. In-vitro plate assay of AB-11 displayed heat stress tolerance up to 45 °C and salt stress tolerance up to 0.9 M NaCl. The culture filtrate of bacterial isolate AB-11 showed antagonistic activity against two different plant pathogens Pseudomonas syringae pv. tomato and Xanthomonas campestris with inhibition zones 26 ± 1 mm and 21 ± 1 mm respectively. Due to increase in world's population by 2050, sustainable agricultural practices as envisaged in United Nations (UN) Sustainable Development Goals (SDGs) are being focused nowdays, thus the role of AB-11 supplementation both by primary inoculation (1°) using seed biopriming and subsequent secondary inoculation (2°) (supplementation in plants) in chickpea plants was investigated. Bioinoculation led to increase in root length (25.52%), fresh weight (37.10%), relative water content (10.94%) and total chlorophyll content (37.28%). Development of shoot and root system was also prominent due to multiple branching in shoots and roots and appearance of numerous root hairs was also observed. This is the first study related to Streptomyces sp. from A. parviflora which suggests that Streptomyces sp. (AB-11) can be considered as a sustainable bioadditive.