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.
Highlights
Phytophthora capsici is a notorious fungus which infects many crop plants at their early and late growth stages
Results from our studies indicated that seed treatment with bacterial strains significantly enhanced the seed germination over untreated control, and no phytotoxicity was observed in any treatment and our results are supported by the finding o f75
Results from our study indicate that seed treatment with Plant growth promoting rhizobacteria (PGPR) significantly reduced the seedling mortality and disease severity of P. capsici in chilli pepper and studies have proved the role of rhizobacteria as biological control agents[81,82]
Summary
Phytophthora capsici is a notorious fungus which infects many crop plants at their early and late growth stages. 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. 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]. Bacteria are abundant microbes within the soil, and many of them have plant growth promotion traits known as P GPRs5 Their mechanism of action includes the production of indole-3-acetic acid (IAA), nitrogen fixation, soil phosphorus solubilization and various nutrients, and antagonism against pathogens by siderophores, cellulose, protease, antibiotics and cyanide production[6]. The present study is designed to isolate, characterize, to test the disease suppressiveness and PGP effects of native rhizobacterial strains, recovered from chilli rhizosphere. This study will help to explore the potential of these bacterial strains against other soil-borne pathogens and bio-pesticide development
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