Sub Programme Area 303
Research on diversity assessment of the dimethylsulfoniopropionate (DMSP) bacterial communities of the mangrove ecosystem contributing to the sulfur cycle is continuing. The whole-genome sequence of the Pseudomonas sp. MSSRFD41 extensively tested under field conditions was analysed. Further, microbe-mediated biofortification of iron (Fe) and zinc (Zn) in rice by identifying micronutrient-mobilizing bacterial isolates is continuing. In addition, about 37 genotypes of finger millet, including both traditional and improved varieties, were evaluated for abiotic stress tolerance.
303.1 Microbial Community Profiling of Mangrove Ecosystem
Novel Insights into Bacterial Cycling of Dimethylsulfoniopropionate and Related Molecules in South Indian Mangrove Ecosystem: The study on exploring the DMSP-synthesizing and -degrading bacterial communities of the Pichavaram mangroves of South India continued. A total of 950 bacterial isolates from nine different soil samples of the Pichavaram mangroves isolated through enrichment culturable method in DMSP-amended media were selected based on distinctive morphotype and screened for DMSP-synthesizing and -catabolizing genes. Of these, 50 isolates showed positive amplification for DMSP-synthesizing genes with -24 dsyB and -15 mmtN compared with reference-type strains Labrenzia aggregate LZ033 and Novosphingobium sp. BW1, and one strain positive for both dsyB and mmtN. About 66 strains involved in DMSP catabolism showed positive amplification of the following genes – 4 dmdA, 16 dddP, 33 both dmdA and dddP, 2 mmtN and dddP, 8 dsyB and dddP, 3 dddD – compared with reference strains Ruegeria pomeroyi DSS-3 (dmdA and dddP) and Pseudovibrio P12 (dddD). BOX-PCR-based genetic diversity analysis of the total 106 positive isolates formed 67 clusters indicating the diverse groups involved in DMSP cycling. The taxonomical position determined by 16S rRNA sequencing analysis revealed that the isolates mostly belonged to the Roseobacter group. The majority of the isolates participating in DMSP synthesis and catabolism were isolated from the rhizospheric soils of Avicennia marina and Rhizophora mucronata indicating the rhizospheric region as active zones of DMSP cycling in the mangrove ecosystem. Thus, the MSSRF study will provide deeper insights into the diversity of DMSP-synthesizing and -degrading bacterial communities associated with the mangrove ecosystems that contribute to DMSP synthesis, which functions as a key marine nutrient in the microbial food web and the global sulfur cycle, a chemoattractant for marine organisms and a major precursor for the climate active gases dimethylsulfide (DMS) and methanethiol (MeSH).
303.2 Whole-Genome Sequencing of Pseudomonas sp. MSSRFD41
Whole-Genome Analysis of Novel Pseudomonas sp. MSSRFD41: Pseudomonas sp. MSSRFD41 isolated from finger millet rhizosphere holds several plant-growth-promoting and disease-protection traits. The whole genome of strain MSSRFD41 was sequenced using both Illumina Hiseq and Pacbio platforms. A total of 378673 PacBio long reads and 21673550 Illumina short reads were obtained in good quality with an average of 50 bp per read. The sequence assembly produced 65 contigs representing one chromosome having an approximate size of 6053738 bp with a G+C content of 62 per cent. Further, several genes coding for plant-growth-promoting traits, such as osmotic tolerance, lytic enzymes, siderophore biosynthesis, cobalt-zinc-cadmium resistance, phosphodiesterase/alkaline phosphatase, acid phosphatase, dicarboxylate MFS transporter and Na+/H+ antiporter, were identified. The whole genome sequence data will be deposited at the National Centre for Biotechnology Information (NCBI), and the manuscript is under preparation.
303.3 Microbe-Mediated Biofortification of Rice by Enhancing Bioavailability of Iron and Zinc in Soil Using Plant-Growth-Promoting Rhizobacteria (PGPR)
Microbe-mediated biofortification of rice with zinc and iron can be a viable option to overcome low dietary intake and micronutrients deficiency. India being the second-largest producer and consumer of rice accounts for 22.3 per cent of global production; therefore, the present investigation is being carried out to evaluate the potential of micronutrient-mobilizing plant-growth-promoting rhizobacteria (PGPR) for enhancing the zinc and iron content in the edible portion of rice. The rhizosphere soils of about 12 different rice varieties, namely, ADT37, ADT45, ADT43, ASD16, IR50, IR37, CO51, Vellaikar, Andhraponni, IR32, VellaiPonni and SonaMasuri, cultivated in Cuddalore and Villupuram districts of Tamil Nadu were screened for obtaining potential iron- and zinc-mobilizing bacterial isolates. Different zinc sources (e.g., ZnO2, ZnCO3, ZnSO4, Zn3 (PO4)2) and chrome azurols (CAS) agar were used. About 41 zinc-mobilizing, 45 iron-mobilizing and 14 bacterial strains with both zinc- and iron-mobilizing activity were identified by qualitative assay. In addition, these isolates exhibited plant-growth-promoting traits, namely, indole acetic acid (IAA), ammonia production and biocontrol activity against Rhizoctonia solani. Further, taxonomic identification and quantification of zinc- and iron-mobilization potential is in progress.
303.4 Screening of Drought and Salinity Tolerance in Traditional and Improved Finger Millet Varieties
Finger millet is a climate-smart, nutri-dense crop widely cultivated in rain-fed semiarid tropics. In this study, 37 different finger millet varieties, both traditional (22) and improved (15), obtained from MSSRF-Jeypore seed bank, were screened for drought tolerance using polyethylene glycol (PEG) 8000 at 10, 15 and 20 per cent, and salinity tolerance at 50, 100, 150 and 200 mM NaCl conc. under in vitro conditions. Among the varieties screened for salinity tolerance, traditional varieties Duseramandia and Tayamandia and improved varieties Arjun, MR-1, HR-911, GPU-48 and ML 365 showed 90 and 80 per cent seed germination in 150 and 200 mM NaCl conc., respectively. In drought-tolerance assay, traditional varieties Bhairabi and Duseramandia and improved varieties Arjun and HR-911 showed 85 per cent seed germination in 20 per cent PEG, while in 15 per cent PEG, 90 per cent germination was observed in traditional varieties Murdamandia, Birimandia and Kurkutimandia and in improved varieties HR-911, MR-1, Subhara, GPU-28, ML 365 and Arjun. The improved varieties predominantly showed higher levels of tolerance to drought and salinity stress compared with traditional varieties. Further, the significant tolerance level of these varieties to drought and salinity stress needs to be evaluated. Also, comparing of the core microbiome profiles among the tolerant varieties and classifying unique abiotic alleviating traits will lead to the identification of efficient plant-growth-promoting strains to promote eco-friendly agriculture under abiotic stress.