Secondary metabolite induced tolerance to Fusarium oxysporum f.sp. cubense TR4 in banana cv. Grand Naine through in vitro bio-immunization: a prospective research translation from induction to field tolerance.

An innovative tissue culture mediated incorporation of metabolite-based biomolecule (Bio-immune) at in vitro stage itself in banana cv. Grand Naine was developed and validated for the production of Fusarium oxysporum f.sp. cubense TR4 tolerant plantlets. The novel bio-immune formulation developed by us, exhibited a significant antifungal potency against Foc TR4 with a high percent inhibition (100%) at a 2.5% concentration of bio-immune on the 5th, 7th, and 9th DAI. Bio-immune integrated during in vitro shoot proliferation stage in banana cv. Grand Naine recorded significant enhancement in the growth of roots and shoots. Bio-immune (0.5%) fortified media produced 12.67 shoots per clump whereas control registered only 9.67 shoots per clump. Similarly, maximum root numbers (7.67) were observed in bio-immune plants which were significantly higher over control (5.0). The bio-immunized banana transplants recorded a higher survival rate (97.57%) during acclimatization as compared to the control (94.53%). Furthermore, evaluation of the bio-immunized plants in pot experiments revealed that unimmunized plants treated with FocTR4 (TF) exhibited mortality between 60 and 90 days. On the 90th day after planting, a high mean disease severity index (DSI) of 3.45 was observed with unimmunized plantlets while the bio-immunized plants (TFBI) and ICAR-FUSICONT treated plants (TFTR) showed substantially reduced DSI (0.20 and 1.00) compared to FocTR4 treated control (TF). Significant increases in polyphenol oxidase (PPO), peroxidase (POD), ß-1,3-glucanase, phenylalanine ammonia-lyase (PAL), chitinase activities, and enhanced phenol contents were recorded in bio-immunized plants compared to unimmunized plants. Field experiments at two different locations in Bihar, India revealed that bunch weight, no. of hands/bunch, and no. of fingers/hand of bio-immune treated plants were significantly higher compared to the control.

Exploration of Klebsiella pneumoniae M6 for paclobutrazol degradation, plant growth attributes, and biocontrol action under subtropical ecosystem.

In recent times, injudicious use of paclobutrazol (PBZ) in mango orchards deteriorates the soil quality and fertility by persistence nature and causes a serious ecosystem imbalance. In this study, a new Klebsiella pneumoniae strain M6 (MW228061) was isolated from mango rhizosphere and characterized as a potent plant growth promoter, biocontrol, and PBZ degrading agent. The strain M6 efficiently utilizes PBZ as carbon, energy and nitrogen source and degrades up to 98.28% (50 mgL-1 initial conc.) of PBZ at 15th day of incubation in MS medium. In the soil system first order degradation kinetics and linear model suggested 4.5 days was the theoretical half-life (t1/2 value) of PBZ with strain M6. Box Behnken design (BBD) model of Response surface methodology (RSM) showed pH 7.0, 31°C temperature, and 2.0 ml inoculum size (8 x 109 CFU mL-1) was optimized condition for maximum PBZ degradation with strain M6. Plant growth promoting attributes such as Zn, K, PO4 solubilization IAA, HCN and NH3 production of strain M6 showed positive results and were assessed quantitatively. The relation between plant growth promotion and PBZ degradation was analyzed by heat map, principal component analysis (PCA) and, clustal correlation analysis (CCA). Strain M6 was also showing a significant biocontrol activity against pathogenic fungi such as Fusarium oxysporum (MTCC-284), Colletotrichum gloeosporioides (MTCC- 2190), Pythium aphanidermatum (MTCC- 1024), Tropical race 1 (TR -1), and Tropical race 4 (TR -4). Hence, results of the study suggested that strain M6 can be utilized as an effective bio-agent to restore degraded land affected by persistent use of paclobutrazol.

Bacterial structure and dynamics in mango (Mangifera indica) orchards after long term organic and conventional treatments under subtropical ecosystem.

This study explores the comparative effect of conventional and organic treatments on the rhizosphere microbiome of Mangifera indica cv. Dashehari. The long-term exposures (about 20 years) were monitored under a subtropical ecosystem. Based on plant growth properties and acetylene reduction assay, 12 bacterial isolates (7 from G1-organic and 5 from G2-conventional systems) were identified as Pseudomonas and Bacillus spp. In the conventional system, dehydrogenase activity significantly decreased (0.053 µg TPF formed g-1 of soil h-1) and adversely affected the bacterial diversity composition. In comparison, organic treatments had a good impact on dehydrogenase activity (0.784 µg TPF formed g-1 of soil h-1), alkaline phosphatase (139.25 µg PNP g-1 soil h-1), and bacterial community composition. The Metagenomics approach targeted the V3 and V4 regions to see the impact in the phylum, order, family, genus, and species for both the treatments. Results showed that phylum Acidobacteria (13.6%), Firmicutes (4.84%), and Chloroflexi (2.56%) were dominating in the G2 system whereas phylum Bacteroides (14.55%), Actinobacteria (7.45%), and Proteobacteria (10.82%) were abundantly dominated in the G1 system. Metagenome sequences are at the NCBI-GenBank sequence read archive with SRX8289747 (G1) and SRX8289748 (G2) in the study PRJNA631113. Results indicated that conventional and organic conditions affect rhizosphere microbiome and their environment.

Mechanisms and kinetics for the degradation of paclobutrazol and biocontrol action of a novel Pseudomonas putida strain T7.

The present study explores biodegradation kinetics and process optimization of plant growth retardant from triazole group paclobutrazol (PBZ; C15H20ClN3O mol. wt. 293.79 g mol-1) in a batch experiment. A gram-negative rod-shaped bacterium T7 was isolated from PBZ applied agricultural field by enrichment technique and characterized as Pseudomonas putida strain T7. Strain was tested for PBZ biodegradation and plant growth-promoting characteristics. Results revealed that strain T7 utilizes PBZ as a carbon and energy source and showing degradation up to 98.30% on the 15th day. First-order degradation kinetics and a linear model were well fitted and showing a maximum t1/2 value on 9th day. Biodegradation optimization by Box Behnken design (BBD) of Response surface methodology (RSM) showed maximum degradation at pH 7.0, 31 °C temperature, and 2 mL inoculum size (8 × 109 CFU mL-1). The bacterium was also able to solubilize Zn, K, and PO4 and produced a copious amount of IAA, HCN, and Ammonia. The biocontrol activity against plant pathogens like Fusarium oxysporum (MTCC-284), Colletotrichum gloeosporioides (MTCC 2190), Pythium aphanidermatum (MTCC - 1024), Tropical race-1 (TR -1), and Tropical race - 4 (TR-4) showed the great antagonistic effect. Hence, this strain can be employed as an effective bio-agent for eco-friendly cleanup strategies and pathogen suppressive agents in paclobutrazol contaminated soil.

Biological Management of Banana Fusarium Wilt Caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 Using Antagonistic Fungal Isolate CSR-T-3 (Trichoderma reesei).

Fusarium wilt in bananas is one of the most devastating diseases that poses a serious threat to the banana industry globally. With no effective control measures available to date, biological control has been explored to restrict the spread and manage the outbreak. We studied the effective biological control potential of different Trichoderma spp. in the management of Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4). Expression of the defense related genes and metabolites in banana plants inoculated with Foc TR4 and treated with effective Trichoderma sp interactions were also studied. The in vitro growth inhibition of Foc TR4 by Trichoderma reesei isolate CSR-T-3 was 85.19% indicating a higher antagonistic potential than other Trichoderma isolates used in the study. Further, in in vivo assays, the banana plants treated with the isolate CSR-T-3 T. reesei had a significant reduction in the disease severity index (0.75) and also had increased phenological indices with respect to Foc TR4 treated plants. Enhanced activity of defense enzymes, such as ß-1, 3-glucanase, peroxidase, chitinase, polyphenol oxidase, and phenylalanine ammonia lyase with higher phenol contents were found in the Trichoderma isolate CSR-T-3 treated banana plants challenge-inoculated with Foc TR4. Fusarium toxins, such as fusaristatin A, fusarin C, chlamydosporal, and beauveric acid were identified by LC-MS in Foc TR4-infected banana plants while high intensity production of antifungal compounds, such as ß-caryophyllene, catechin-o-gallate, soyasapogenol rhamnosyl glucoronide, peptaibols, fenigycin, iturin C19, anthocyanin, and gallocatechin-o-gallate were detected in T. reesei isolate CSR-T-3 treated plants previously inoculated with Foc TR4. Gene expression analysis indicated the upregulation of TrCBH1/TrCBH2, TrXYL1, TrEGL1, TrTMK1, TrTGA1, and TrVEL1 genes in CSR-T-3 treatment. LC-MS and gene expression analysis could ascertain the upregulation of genes involved in mycoparasitism and the signal transduction pathway leading to secondary metabolite production under CSR-T-3 treatment. The plants in the field study showed a reduced disease severity index (1.14) with high phenological growth and yield indices when treated with T. reesei isolate CSR-T-3 formulation. We report here an effective biocontrol-based management technological transformation from lab to the field for successful control of Fusarium wilt disease caused by Foc TR4 in bananas.

MiSNPDb: a web-based genomic resources of tropical ecology fruit mango (Mangifera indica L.) for phylogeography and varietal differentiation.

Mango is one of the most important fruits of tropical ecological region of the world, well known for its nutritive value, aroma and taste. Its world production is >45MT worth >200 billion US dollars. Genomic resources are required for improvement in productivity and management of mango germplasm. There is no web-based genomic resources available for mango. Hence rapid and cost-effective high throughput putative marker discovery is required to develop such resources. RAD-based marker discovery can cater this urgent need till whole genome sequence of mango becomes available. Using a panel of 84 mango varieties, a total of 28.6 Gb data was generated by ddRAD-Seq approach on Illumina HiSeq 2000 platform. A total of 1.25 million SNPs were discovered. Phylogenetic tree using 749 common SNPs across these varieties revealed three major lineages which was compared with geographical locations. A web genomic resources MiSNPDb, available at http://webtom.cabgrid.res.in/mangosnps/ is based on 3-tier architecture, developed using PHP, MySQL and Javascript. This web genomic resources can be of immense use in the development of high density linkage map, QTL discovery, varietal differentiation, traceability, genome finishing and SNP chip development for future GWAS in genomic selection program. We report here world's first web-based genomic resources for genetic improvement and germplasm management of mango.