Characterization of native plant growth promoting rhizobacteria and their anti-oomycete potential against Phytophthora capsici affecting chilli pepper (Capsicum annum L.)

Abstract

Phytophthora capsici is a notorious fungus which infects many crop plants at their early and late growth stages. in the present study, twelve P. capsici isolates were morphologically characterized, and based on pathogenicity assays; two highly virulent isolates causing post-emergence damping-off on locally cultivated chilli pepper were screened. two P. capsici isolates, HydPak1 (MF322868) and HydPk2 (MF322869) were identified based on internal transcribed spacer (ITS) sequence homology. Plant growth promoting rhizobacteria (PGPR) play a significant role in disease suppression and plant growth promotion in various crops. Out of fifteen bacterial strains recovered from chilli rhizosphere, eight were found potential antagonists to P. capsici in vitro. Bacterial strains with strong antifungal potential were subjected to biochemical and molecular analysis. All tested bacterial strains, were positive for hydrogen cyanide (HCN), catalase production and indole-3-acetic acid (IAA) production (ranging from 6.10 to 56.23 µg ml −1), while siderophore production varied between 12.5 and 33.5%. The 16S rRNA sequence analysis of tested bacterial strains showed 98-100% identity with Pseudomonas putida, P. libanensis, P. aeruginosa, Bacillus subtilis, B. megaterium, and B. cereus sequences available in the National Center for Biotechnology Information (NCBI) GenBank nucleotide database. All sequences of identified bacteria were submitted to GenBank for accessions numbers (MH796347-50, MH796355-56, MH801129 and MH801071). Greenhouse studies concluded that all tested bacterial strains significantly suppressed the P. capsici infections (52.3-63%) and enhanced the plant growth characters in chilli pepper. Efficacy of many of these tested rhizobacteria is being first time reported against P. capsici from Pakistan. Plant growth promoting rhizobacteria (PGPR) exhibiting multiple traits may be used in the development of new, eco-friendly, and effective bioformulations as an alternative to synthetic fungicides. Chilli, also red pepper or chilli pepper (Capsicum annuum L.) is among the extensively grown spice crop in Pakistan like many other countries around the globe. Quality and quantity of the crop are adversely affected by numerous soil-borne and areal pathogens of which Phytophthora capsici is one of the most devastating oomycete pathogens, resulting into damping-off and blight diseases 1. This pathogen causes complete crop failure under favorable environmental conditions 2. Synthetic pesticides are frequently applied to attain a high yield of the produce however, this disease management strategy comes with potential risks to the environment and human

Characterization and Diversity of plant growth promoting Endophytic and Rhizosphere Bacteria isolated from theRhizosphere and tissues of Pepper and their effect on plant growth promotion and disease suppression of Phytophthora capsici

“…Concerning the isolated bacteria, 11.67 % were from roots, 63.33 % from the rhizosphere, 8.3 % from leaves and 11 % from stem. Previous studies also report on various biocontrol potential of bacteria belonging to the genera Pseudomonas and Bacillus 36 , Bacillus subtlis and Actinomycetes 37 being the most common bacterial groups showing in pepper plants. Bacterial colonization appeared to be abundant in the rhizosphere pepper plants, which may be a re ection of a primary site for bacterial nutrients.…”

“…V.H.18, AULE41-Pseudomonas uorescence and AAULE51-un identi ed showed > 52.5% mycelial growth inhibition of Phytophthora capsici. 36 studied the antagonistic effects of bacterial strains and found that, out of fteen tested rhizospheric bacteria, ve bacterial strains showed > 70% of antagonistic potential against P.capsici. In other study from 48 threeisolates were found to control P.capsici both in vivo and in vitro 44 .…”

Seed treatment using rhizobacteria as plant growth promotion of two chili variety (Capsicum annuum L.)

“…Auxinitriggersiainumber of cellularifunction rangingifrom differentiationiof vascular tissues,iinitiation ofilateral and adventitiousiroots, stimulation oficell division, elongationiof stems andiroots, and orientationiof root and shoot growth in response to light and gravity [21,22]. Six rhizobacteria strains, were produce IAA that able to increased shoot, stem and root length of chilli pepper [23].…”

Reflections and Insights on the Evolution of the Biological Remediation of Contaminated Soils

“…1aminocyclopropane-1-carboxylate deaminase activity, nitrogen fixation, phosphorus solubilization, potassium solubilization, indolacetic acid production, siderophore production, production of hydrolytic enzymes (e.g., α-amylase, cellulase, chitinase, pectinase, protease), antibiotic production, hydrogen cyanide production, ammonia production, fungal antagonistic activity, etc. (Glick, 2012;Dinesh et al, 2015;Burges et al, 2017;Hyder et al, 2020). It must be emphasized that all these lab-tested traits only represent potentiality but not reality, since the inoculated microbial strains must also show ecological competence and functional performance in the specific soilplant system under consideration (actually, in many cases, they do not survive or grow properly, or do not produce the required phenotype, once they have been inoculated) (Nelson, 2004;Backer et al, 2018).…”