Plant growth-promoting rhizobacteria (PGPR) is a microbial population found in the rhizosphere of plants that can stimulate plant development and restrict the growth of plant diseases directly or indirectly. In this study, 90 rhizospheric soil samples from five agro climatic zones of chilli (Capsicum annuum L.) were collected and rhizobacteria were isolated, screened and characterized at morphological, biochemical and molecular levels. In total, 38% of rhizobacteria exhibited the antagonistic capacity to suppress Ralstonia solanacearum growth and showed PGPR activities such as indole acetic acid production by 67.64% from total screened rhizobacteria isolates, phosphorus solubilization by 79.41%, ammonia by 67.75%, HCN by 58.82% and siderophore by 55.88%. We performed a principal component analysis depicting correlation and significance among plant growth-promoting activities, growth parameters of chilli and rhizobacterial strains. Plant inoculation studies indicated a significant increase in growth parameters and PDS1 strain showed maximum 71.11% biocontrol efficiency against wilt disease. The best five rhizobacterial isolates demonstrating both plant growth-promotion traits and biocontrol potential were characterized and identified as PDS1—Pseudomonas fluorescens (MN368159), BDS1—Bacillus subtilis (MN395039), UK4—Bacillus cereus (MT491099), UK2—Bacillus amyloliquefaciens (MT491100) and KA9—Bacillus subtilis (MT491101). These rhizobacteria have the potential natural elicitors to be used as biopesticides and biofertilizers to improve crop health while warding off soil-borne pathogens. The chilli cv. Pusa Jwala treated with Bacillus subtilis KA9 and Pseudomonas fluorescens PDS1 showed enhancement in the defensive enzymes PO, PPO, SOD and PAL activities in chilli leaf and root tissues, which collectively contributed to induced resistance in chilli plants against Ralstonia solanacearum. The induction of these defense enzymes was found higher in leave tissues (PO—4.87-fold, PP0—9.30-fold, SOD—9.49-fold and PAL—1.04-fold, respectively) in comparison to roots tissue at 48 h after pathogen inoculation. The findings support the view that plant growth-promoting rhizobacteria boost defense-related enzymes and limit pathogen growth in chilli plants, respectively, hence managing the chilli bacterial wilt.

Microbial volatiles benefit the agricultural ecological system by promoting plant growth and systemic resistance against diseases without harming the environment. To explore the plant growth-promoting efficiency of VOCs produced by Pseudomonas fluorescens PDS1 and Bacillus subtilis KA9 in terms of chili plant growth and its biocontrol efficiency against Ralstonia solanacearum, experiments were conducted both in vitro and in vivo. A closure assembly was designed using a half-inverted plastic bottle to demonstrate plant–microbial interactions via volatile compounds. The most common volatile organic compounds were identified and reported; they promoted plant development and induced systemic resistance (ISR) against wilt pathogen R. solanacearum. The PDS1 and KA9 VOCs significantly increased defensive enzyme activity and overexpressed the antioxidant genes PAL, POD, SOD, WRKYa, PAL1, DEF-1, CAT-2, WRKY40, HSFC1, LOX2, and NPR1 related to plant defense. The overall gene expression was greater in root tissue as compared to leaf tissue in chili plant. Our findings shed light on the relationship among rhizobacteria, pathogen, and host plants, resulting in plant growth promotion, disease suppression, systemic resistance-inducing potential, and antioxidant response with related gene expression in the leaf and root tissue of chili.

Mustard (Brassica juncea L.) is an important oil seed crop in the Brassicaceae family. It is widely cultivated in India for its edible leaves, oil and medicinal properties. In January 2022, we noti...

India is one of the leading citrus−producing countries, next to China and Brazil. Despite the sizeable production, especially of lemons and limes, India contributes meagerly to the world’s citrus market. Of the various factors responsible for the restricted quantum of citrus export, citrus canker (Xanthomonas citri pv. citri) is one of the leading serious causes and directly impacts the appearance of the fruits. Considering the extent of damage, the present study aimed to understand the impact of Xanthomonas citri pv. citri (Xcc) on the physio−biochemical responses in contrasting Citrus spp. Two genotypes, each of three citrus species, namely Citrus aurantifolia (Pusa Udit and ALC−35), C. limon (Kagzi Kalan and Konkan Seedless), and C. paradisi (Redblush and Marsh Seedless), were artificially inoculated with Xcc (10⁸ to 10⁹ cfu/ mL) by the pinprick method. The physio−biochemical changes in the host were evaluated after 48 h post inoculation (hpi). The chlorophyll content (total, a, and b) degradation and reduction in leaf gas exchange parameters, such as photosynthetic rate (A), transpiration rate (E), stomatal conductance (g_s), and intrinsic water−use efficiency (iWUE), were measured to a greater extent in susceptible than resistant genotypes. The microscopic observations also evidenced higher stomatal density with larger stomatal areas in susceptible genotypes, favoring the easier penetration of Xcc in host tissues than resistant species or genotypes. The higher activities of various antioxidant enzymes, viz., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), the contents of soluble protein, and phenolics were measured in resistant genotypes in contrast to susceptible genotypes. The activities of phenyl ammonia lyase (PAL) and polyphenol oxidase (PPO) were also higher in resistant genotypes, whilst the levels of ROS (superoxide radical and hydrogen peroxide) production were enhanced in susceptible genotypes. Based on the host–pathogen interaction, the order of resistance in a descending manner was found as Kagzi Kalan, Marsh Seedless, Redblush, Konkan Seedless, Pusa Udit, and ALC−35. Further, the results will enhance the understanding of the pathogen mechanism during pathogenesis in resistant and susceptible Citrus species.

The Brassica oleracea var. botrytis (cauliflower) is an important annual vegetable crop in the Brassicaceae family and is extensively grown worldwide (Singh et al. 2018). In the early summer of 202...