Evaluation of plant growth promotion properties and induction of antioxidative defense mechanism by tea rhizobacteria of Darjeeling, India

Abstract

A total of 120 rhizobacteria were isolated from seven different tea estates of Darjeeling, West Bengal, India. Based on a functional screening of in vitro plant growth-promoting (PGP) activities, thirty potential rhizobacterial isolates were selected for in-planta evaluation of PGP activities in rice and maize crops. All the thirty rhizobacterial isolates were identified using partial 16S rRNA gene sequencing. Out of thirty rhizobacteria, sixteen (53.3%) isolates belong to genus Bacillus, five (16.6%) represent genus Staphylococcus, three (10%) represent genus Ochrobactrum, and one (3.3%) isolate each belongs to genera Pseudomonas, Lysinibacillus, Micrococcus, Leifsonia, Exiguobacterium, and Arthrobacter. Treatment of rice and maize seedlings with these thirty rhizobacterial isolates resulted in growth promotion. Besides, rhizobacterial treatment in rice triggered enzymatic [ascorbate peroxidase (APX), catalase (CAT), chitinase, and phenylalanine ammonia-lyase (PAL)], and non-enzymatic [proline and polyphenolics] antioxidative defense reactions indicating their possible role in the reduction of reactive oxygen species (ROS) burden and thereby priming of plants towards stress mitigation. To understand such a possibility, we tested the effect of rhizobacterial consortia on biotic stress tolerance of rice against necrotrophic fungi, Rhizoctonia solani AG1-IA. Our results indicated that the pretreatment with rhizobacterial consortia increased resistance of the rice plants towards the common foliar pathogen like R. solani AG1-IA. This study supports the idea of the application of plant growth-promoting rhizobacterial consortia in sustainable crop practice through the management of biotic stress under field conditions.

Plant-PGPR interaction study of plant growth-promoting diazotrophs Kosakonia radicincitans BA1 and Stenotrophomonas maltophilia COA2 to enhance growth and stress-related gene expression in Saccharum spp.

“…Antioxidant enzymes are produced by plants under stress imparted by the reactive oxygen species. Interaction between PGPR and host plants has also been observed to increase the biosynthesis of defense-related molecules under normal conditions that can defend against further attacks by pathogens or other interactions between plant microbes (Cassán et al 2014;Fukami et al 2017;Bhattacharyya et al 2020). The effect on the expression of these enzymes in the plantlets inoculated with the GFP tagged strains was assessed, resulting in enhanced expression of the antioxidant enzymes inoculated with the selected strains as compared to the controls.…”

Diazotrophic Bacteria Pantoea dispersa and Enterobacter asburiae Promote Sugarcane Growth by Inducing Nitrogen Uptake and Defense-Related Gene Expression

“…This is because gene expression is controlled at many different stages and in many different ways such as transcriptional and posttranscriptional regulations (RNA processing, RNA stability, etc.). Previous reports show that rhizosphere microbial inoculation enhances growth and antioxidant enzyme activities in different plants as compared to control under normal conditions ( Bhattacharyya et al, 2020 ; Wang et al, 2020 ). Increased expression of ScChi , ScGluD1 , SuCAT , SuSOD , and S uPAL genes was observed following artificial inoculation of PGP strains in GT11 and GXB9 ( Singh et al, 2020 ) and smut pathogen in sugarcane varieties ( Su et al, 2013 , 2014 ; Singh et al, 2018 , 2019 ).…”

“…PAL provides the plant’s physiological and systemic support by changing L-phenylalanine to trans-cinnamic acid and ammonia. In rice, microbial treatment has been shown to increase the activity of PAL and the aggregation of polyphenols in the leaves, thus helping to enhance stress conditions ( Bhattacharyya et al, 2020 ). By the production of defense-related antioxidant enzymes and molecules, PGPR primes host plants to avoid pathogen attacks ( Choudhary et al, 2007 ).…”

“…The mechanism of ROS detoxification differs with plant species and age and the occurrence and severity of abiotic and biotic stresses plants experience ( Hodges et al, 1996 ). Plant growth-promoting rhizobacteria (PGPR) induce plant defense-related genes such as phenylalanine ammonia-lyase (PAL), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and superoxide dismutase (SOD), which may assist the plant to protect from or reduce the impact of pathogens attacks ( Cassán et al, 2014 ; Fukami et al, 2017 ; Bhattacharyya et al, 2020 ).…”

Indicative Value of the Dominant Plant Species for a Rapid Evaluation of the Nutritional Value of Soils

“…While Peter et al [52] propose the use of Google Earth to select the best biotopes for cultivation, this tool is useful but not satisfactory; the use of bioclimatic maps and the phytosociological study of plant covers is necessary to obtain the amount and type of nutrients ground. Cover crops are necessary to maintain the richness of rhizobacteria, which intervene in the assimilation of nutrients and in plant growth [53,54]. The cover crop acts as a protective element of the soils, which reduces evapotranspiration, minimizing crop irrigation [55,56], and not being necessary the breakages that destroy the soil mycorrhizae that allow the nitrogen entry into nodular systems [57][58][59][60][61].…”