Antifungal Potential of Plant Growth Promoting Bacillus Species Against Blossom Blight of Rose

Blossom blight caused by Botrytis cinerea is one among the most devastating diseases that cause complete post-harvest loss in flower crops. The present study focuses on the development of effective bioformulation towards suppression of blossom blight and plant growth promotion in rose. Bacillus amyloliquefaciens (VB2) and Bacillus subtilis (AP) effectively inhibited mycelial growth of B. cinerea in vitro. Genome screening of VB2 and AP revealed the presence of antimicrobial peptide genes including, ituD, ipa14, bacA, bacD, srfA, sfP, spaC, spaS responsible for the biosynthesis of antibiotics such as iturin, bacilysin, bacillomycin, surfactin and subtilin. Further, the presence of volatile antifungal compounds in the bacterial secretome was identified through gas chromatography–mass spectrometry (GC/MS) analysis. Upon treatment, AP accelerated the metabolite profile of the plants and a rise in peak area of antifungal compounds such as, pentadecanoic acid, n-hexadecanoic acid, octadecanoic acid (stearic acid) and tetradecanoic acid was observed. In vitro, VB2 produced maximum indole acetic acid (9.17 µg/ml) and gibberellic acid (8.20 µg/ml) in nutrient broth. Under field conditions, foliar spray of VB2 at 0.5% (5 ml/l), four times at weekly interval suppressed blossom blight incidence (64% reduction over control) and also promoted yield. Future research towards development of an effective bioformulation with extended shelf life will aid in the management of various fungal, bacterial and viral diseases in different crop plants.

     

PGPR mediated management of stem blight of Phyllanthus amarus (Schum and Thonn) caused by Corynespora cassiicola (Berk and Curt) Wei

Bacillus subtilis (BSCBE4), Pseudomonas chlororaphis (PA23), endophytic P. fluorescens (ENPF1) inhibited the mycelial growth of stem blight pathogen Corynespora casiicola (Berk and Curt)Wei under in vitro. All these bacterial isolates produced both hydroxamate and carboxylate type of siderophores. But the siderophore production was maximum with the isolate ENPF1. Delivering of talc based formulation of BSCBE4 through seedling dip and foliar application effectively reduced stem blight disease incidence and increased the dry matter production under pot culture and field conditions. Application of BSCBE4, PA23 and ENPF1 increased the defense related enzymes such as peroxidase, polyphenol oxidase, chitinase and β-1,3 glucanase in P. amarus up to ten days after challenge inoculation with C. cassicola. Native gel electrophoretic analysis revealed that challenge inoculation of pathogen with BSCBE4 and PA23 induced both peroxidase and polyphnol oxidase isoforms.     

Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves

In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions.     

Multitudinous Potential of Trichoderma Species in Imparting Resistance Against F. oxysporum f. sp. cucumerinum and Meloidogyne incognita Disease Complex

Journal of Plant Growth Regulation - Trichoderma spp. effectively inhibited mycelial growth of Fusarium oxysporum f. sp. cucumerinum F1, egg hatchability and juvenile mobility of M. incognita....     

A GacS deficiency does not affect Pseudomonas chlororaphis PA23 fitness when growing on canola, in aged batch culture or as a biofilm

Pseudomonas chlororaphis PA23 is a biocontrol agent that protects against the fungal pathogen Sclerotinia sclerotiorum. Employing transposon mutagenesis, we isolated a gacS mutant that no longer exhibited antifungal activity. Pseudomonas chlororaphis PA23 was previously reported to produce the nonvolatile antibiotics phenazine 1-carboxylic acid and 2-hydroxyphenazine. We report here that PA23 produces additional compounds, including protease, lipase, hydrogen cyanide, and siderophores, that may contribute to its biocontrol ability. In the gacS mutant background, generation of these products was markedly reduced or delayed with the exception of siderophores, which were elevated. Not surprisingly, this mutant was unable to protect canola from disease incited by S. sclerotiorum. The gacS mutant was able to sustain itself in the canola phyllosphere, therefore, the loss of biocontrol activity can be attributed to a reduced production of antifungal compounds and not a declining population size. Competition assays between the mutant and wild type revealed equivalent fitness in aged batch culture; consequently, the gacS mutation did not impart a growth advantage in the stationary phase phenotype. Under minimal nutrient conditions, the gacS-deficient strain produced a tenfold less biofilm than the wild type. However, no difference was observed in the ability of the mutant biofilm to protect cells from lethal antibiotic challenge.     

Induction of plant defence compounds by Pseudomonas chlororaphis PA23 and Bacillus subtilis BSCBE4 in controlling damping-off of hot pepper caused by Pythium aphanidermatum

Bacillus subtilis strain BSCBE4 and Pseudomonas chlororaphis strain PA23 (=P. aureofaciens) were effective biocontrol agents against Pythium aphanidermatum, the causal agent of damping-off of hot pepper (Capsicum annum L.) in greenhouse vegetable production systems. Application of strains BSCBE4 and PA23 at the rate of 20 g kg^-1 of seed significantly increased the growth of hot pepper seedlings. The efficacies of various carriers in sustaining the population of these strains in storage were assessed. Both the antagonists survived up to 180 days of storage in peat and talc-based formulations. The two bacterial strains induced development of plant defence-related enzymes including phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, phenol content, suppressed incidence of damping-off and increased growth of hot pepper seedlings.     

Aspergillus carbonarius polygalacturonases purified by integrated membrane process and affinity precipitation for apple juice production

Aspergillus carbonarius, when grown by submerged and solid-state fermentation, produces different molecular forms of polygalacturonase (PG; EC 3.2.1.15), among them a 42 kDa PG with a high specific activity of 7000 U/mg protein. When the enzymes were purified by integrated membrane process (IMP) and alginate affinity precipitation (AAP), the two processes concentrated different forms of the enzyme. The AAP process selectively purified and concentrated the high active PG whereas the IMP yielded different PGs and also amylase and protease. Evaluation of the AAP enzyme preparations for apple juice preparation under conditions usually employed commercially demonstrated that the high activity PG did not result in good juice clarity. With IMP processed enzymes, juice yields and clarity were similar to that obtained with commercial PG from A. niger.     

First report of anthracnose on noni caused by Colletotrichum gloeosporioides in India

Noni, an important medicinal plant grown in southern India suffered heavy loss due to anthracnose disease in 2008–2009. Based on their pathogenicity, morphological and cultural characters and ribosomal DNA spacer sequences, the pathogen was identified as Colletotrichum gloeosporioides. This is the first report of anthracnose on noni in India.     

Broad spectrum action of phenazine against active and dormant structures of fungal pathogens and root knot nematode

Antifungal antibiotic from Pseudomonas chlororaphis isolate PA23 was identified as Phenazine using TLC and HPLC. Phenazine recorded the highest inhibition zone of 21?mm with 35.55% percent inhibition of mycelial growth of Pythium aphanidermatum over control. It had a significant effect on the hyphal morphology of P. aphanidermatum and on spore germination of Botryodiplodia theobromae and Alternaria solani. Disorganization of hyphal morphology of P. aphanidermatum includes vacuolization, cell content degeneration and hyphal lysis. Similarly interaction of phenazine with Rhizoctonia solani resulted in abnormal swelling of hyphal tips was noticed in the hyphal tips. Similarly the germination of sclerotia of Macrophomina phaseolina, R. solani and Sclerotium rolfsii were completely inhibited by phenazine at a concentration 50?μl. Incubation of the eggs of the root knot nematode Meloidogyne incognita in 30?μl concentration of phenazine, completely suppressed the hatching of juveniles.     

Differential bacterial endophytome in Foc-resistant banana cultivar displays enhanced antagonistic activity against Fusarium oxysporum f.sp. cubense (Foc)

Diverse endophytes with multiple functions exist in different banana cultivars. However, the diversity of cultivable bacterial endophytome that contributes to antifungal activity against Fusarium oxysporum f.sp. cubense (Foc) in resistant and susceptible banana cultivars is mostly unknown. In the present study, we isolated bacterial endophytes from resistant Yengambi KM5 (AAA) and susceptible banana cultivar Ney Poovan (AB) to determine the diversity of cultivable bacterial endophytes. Our study revealed the presence of 56 cultivable bacterial endophytes and 6 nectar-associated bacteria in YKM5 and 31 cultivable bacterial endophytes in Ney Poovan. The identified cultivable bacterial genera in YKM5 included Alcaligenes, Arthrobacter, Azotobacter, Acinetobacter, Agrobacterium, Bacillus, Brucella, Brevundimonas, Brachybacterium, Beijerinckia, Klebsiella, Leclercia, Lysinibacillus, Myroides, Ochrobactrum, Pseudomonas, Rhizobium, Stenotrophomonas, Serratia, and Verticiella. In Ney Poovan, the cultivable endophytic bacterial genera present were Agrobacterium, Bacillus, Bradyrhizobium, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Rhizobium, and Sphingobium. Thus, the composition and diversity of cultivable endophytic bacterial genera were higher in Foc-resistant YKM5. The antifungal efficacy of bacterial endophytes Brachybacterium paraconglomeratum YEBPT2 (65.5%), Brucella melitensis YEBPS3 (63.3%), Bacillus velezensis YEBBR6 (63.3%), and nectar-associated Bacillus albus YEBN2 (61.1%) from YKM5 showed the highest antifungal activity against Foc, compared with the antifungal activity of endophytes from the susceptible cultivar.