Pesticidal Activity of Sundarban Mangrove Plant Extracts against Sitophilus Pests and Identification of Active Constituents Using LC-MS

Plants act as a rich source of novel natural pesticides. In the backdrop of the recent revival of interest in developing plant-based insecticides, this study was carried out to investigate the pesticidal activity of Sundarban mangrove plants. A total of nine different plant parts from five plants, namely, Aegiceras corniculatum, Excoecaria agallocha, Heritiera fomes, Xylocarpus moluccensis, and Xylocarpus granatum, were extracted with methanol and tested for insecticidal activity against two common stored product pests Sitophilus oryzae and Sitophilus zeamais using direct contact feeding deterrent wafer disc method. Three bark extracts from A. corniculatum, E. agallocha, and H. fomes showed potent and statistically significant insecticidal activity against both S. oryzae and S. zeamais pests (80–100% mortality). All the active bark extracts were further fractionated using C-18 solid-phase extraction (SPE) columns and tested for their insecticidal activity against S. oryzae pest to identify the active fraction. Only the SPE4 fraction (100% MeOH) from all the three active plants showed the activity against S. oryzae pest with a lethal concentration 50% (LC50) value of 0.5, 1.0, and 1.5 mg/disc for A. corniculatum, E. agallocha, and H. fomes, respectively. The active fraction of A. corniculatum was further profiled for identification of active compounds using LC-ESI-MS and identified (along with some unknown peaks) two previously reported compounds at m/z 625.17630 (isorhamnetin 3-O-rutinoside) and 422.25346 (paspaline) as major constituents. Insecticidal activities of these plants are reported in this study for the first time and would be useful in promoting research aiming for the development of new biopesticides from mangrove plants.

Dynamics of salinity intrusion in the surface and ground water of Sundarban Biosphere Reserve, India

Sundarban is the world’s largest transboundary contiguous mangrove ecosystem and home of the mangrove dwelling tigers. Sea level rise is destabilizing this ecosystem which is experiencing a rising salinity in surface and ground waters (shallow aquifer). In this study ground water salinity was investigated across Sundarbans and surface water seasonal salinity changes has been investigated along East-west gradient in the region. Statistically significant seasonal as well as spatial variations has been observed in the surface water salinity pattern across this gradient. The post monsoon average surface water salinity was 10.58 ppt while in pre-monsoon it was 27.31 ppt. Ground water salinity was lowest (0.95 ppt) in monsoon while highest in the pre-monsoon season (7.4 ppt). There was a clear east-west gradient in the surface salinity distribution across the delta, indicating a source of fresh water in the eastern corner, bordering Bangladesh. Increasing salinity indicate impact on mangrove diversity with salinity sensitive species (Heritiera fomes, Nypa fruticans) limited to the eastern corner while salinity resilient species (Avicennia marina and Phoenix paludosa) were dominating the western and central part of the Indian Sundarbans. Mangrove associate Acanthus ilicifolius and Heliotropium currasavicum were abundant in the forests under anthropogenic disturbances.

Population status of Heritiera fomes Buch.-Ham., a threatened species from Mahanadi Mangrove Wetland, India

Heritiera fomes Buch.-Ham. is assessed as an endangered mangrove species by IUCN, and information on population status is lacking. The present study assesses the status of H. fomes in Mahanadi Mangrove Wetland on the east coast of India. Three forest blocks were selected and sampled for this study. Among these, the mean girth at breast height (GBH) of H. fomes was the highest in Hetamundia (HD) forest block. GBH of H. fomes was inversely proportional to the cumulative disturbance index (R2= 0.7244, p value <0.005). The relative density was maximum for H. fomes (56%) at Bhitarkharnasi (BK), and for Excoecaria agallocha at Hetamundia (HD; 35%) & Kansaridia (KD; 54%), respectively. Excoecaria agallocha is a dominant species possibly impacting natural populations of H. fomes. Climate change and rising sea levels may also negatively affect the existence of this species. Therefore, appropriate strategies should be taken for conservation of this globally threatened mangrove species prior to its extinction.

Growth and Yield of Avicennia Officinalis (Baen) L. And Heritiera Fomes (Sundri) Buch. Ham. Plantations Established From Plus Tree Seeds in the Western Coastal Belt of Bangladesh

not available Asiat. Soc. Bangladesh, Sci. 46(2): 209-214, December 2020

Carbon Stock of Different Parts of Major Plant Species of Three Ecological Zones of Bangladesh Sundarbans

The biomass and carbon sequestration by different parts namely leaf, stem and roots of major dominant plant species of different quadrats established in three ecological zones of Bangladesh Sundarban Mangrove Forests (SMF) were determined. A visit was done during 28 March to 1 April 2016 covering the oligohaline, mesohaline and polyhaline zones of SMF. Plant parts (stem, branch and leaf) of major plant species were collected from 16 quadrats of different locations. The major plant species were selected on the basis of abundance (number). Aboveground biomass (AGB) was estimated as the product of tree volume and wood density. Below ground biomass (BGB) were estimated from the 20% of above ground stem biomass. Carbon stock and CO2 sequestration were estimated from the dry weight of AGB and BGB. A total of 20 species in 16 different quadrats in three ecological zones and overall SMF was recorded. Among 20 species 10 dominant tree species were considered on the basis of abundance (number) for the estimation of AGB, BGB and CO2 sequestration. Species wise mean AGB (ton/ha) of 10 dominant mangrove trees are in order Heritiera fomes (186.423) > Excoecaria agallocha (28.752) > Avicennia officinalis (24.082) > Ceriops decandra (5.021) > Cynometra ramiflora (1.403) > Tamarix dioica (0.592) > Xylocarpus moluccensis (0.500) > Bruguiera gymnorrhiza (0.307) > Aegiceras corniculata (0.241) > Aglaia cuculata (0.038).Species wise mean BGB (ton/ha) of 10 dominant mangrove trees are in order H. fomes (34.99) > E. agallocha (4.94) > A. officinalis (4.79) > C. decandra (0.704) > X. moluccensis (0.47) > C. ramiflora (0.15) > B. gymnorrhiza (0.018) > A. corniculata (0.015) > T. dioica (0.008) >A. cuculata (0.004). The total CO2 sequestered (above ground and below ground) in overall SMF (considered land area 4143 km2) was 192.869 megaton. Bangladesh J. Bot. 50(2): 373-385, 2021 (June)

Molecular identification and antimicrobial activity of endophytic fungi isolated from Heritiera fomes (Buch. -Ham), a mangrove plant of the Sundarbans

Background Endophytic fungi play a vital role in plant defense system by secreting various antimicrobial agents. To evaluate the antimicrobial activity of the endophytic fungi of the mangrove plant Heritiera fomes (Buch. -Ham), plants were collected from the Sundarbans, Bangladesh. The endophytic fungi were subsequently isolated and identified. Results Fifty-five endophytic fungi were isolated from the leaves, root, and bark of H. fomes (Buch. -Ham). Genomic DNA was extracted for PCR (polymerase chain reaction) by specific primers to multiply ITS region and sequences were determined. Nucleotide sequence data were submitted to the Genbank and accession number for each fungal strain was obtained. Antimicrobial activity of the ethyl acetate (EtOAc) and methanolic extracts of eleven species from both fermentation and mycelium, respectively, were analyzed by microtiter plate-based antimicrobial assay incorporating resazurin as an indicator of cell growth against two Gram-positive bacteria namely Staphylococcus aureus NCTC 12981 and Micrococcus luteus NCTC 7508, two Gram-negative bacteria namely Escherichia coli NCTC 12241 and Pseudomonas aeruginosa NCTC 12903, and a fungus Candida albicans ATCC 90028. All the endophytic fungal extracts exhibited antimicrobial activities against more than one-tested pathogenic microbial strains. Overall, methanolic extracts showed greater activity than EtOAc extracts. Pseudopestalotiopsis camelliae-sinensis, Pestalotiopsis microspora, and Penicillium copticola were the most active endophytic fungal strains and exhibited strong inhibitory activity against the microorganisms under investigation and their MIC values ranged from 0.0024 to 5.0 mg/mL. Methanolic extracts of both P. camelliae-sinensis and P. microspora showed the highest antibacterial activity (MIC value of 0.0024 mg/mL) against P. aeruginosa NCTC 12903. Conclusion This study showed that the isolated and identified endophytic fungi from H. fomes (Buch. -Ham) could be potential sources of antimicrobial agents.