Agricultural and Food Science

Beclardia macrostachya is one of the rarest orchids in Mauritius. In vitro techniques are being used for mass propagation of this orchid for subsequent restoration programs. Successful asymbiotic germination of Beclardia macrostachya was obtained through embryo rescue under in vitro conditions. Modified half MS medium supplemented with 10% coconut milk was used as basal culture medium and the effect of plant growth regulators at different concentrations on embryo development was assessed through qualitative and quantitative parameters. Diameter of embryos, length of protocorm-like bodies (PLBs) and length of developing shoots were calculated using digital photography. Maximal growth was obtained in treatments without any plant growth regulators and with 0.5 mg/L N6-Benzylaminopurine (BAP). Higher levels of Thidiazuron/TDZ (0.3 mg/L) and BAP (1.0 mg/L) though they stimulated embryo development faster, yielded higher level of necrosis later. The results also suggest that plant growth regulator treatments that stimulate fastest embryo development from immature embryos/ovules need not be reliable for further development to PLB and plantlet regeneration.

Clearing of forest land for agriculture and urbanization following colonization have reduced the forest cover in Mauritius to 3% of total land cover. Today exotic species such as Psidium cattleianum (wild guava), Araucaria columnaris, and Ravenala madagascarensis dominate at Pigeon Wood, the only site in Mauritius where Beclardia can be found, leaving little space for very few indigenous tree species like Labourdonnaisia glauca, Apholoia theiformis and Foetida mauritiana. Beclardia macrostachya is an orchid endemic to Mau-ritius, Madagascar and Reunion. Though it is abundant in the latter countries, it is one of the rarest orchids in Mauritius. An assessment of the factors associated with the stability of this orchid was carried out in forests of these three countries to understand the drastic decline of this orchid in Mauritius. Morphomet-ric and fertility counts carried out at different forests revealed differences in fitness and fertility rates among forests of the same countries and between different countries. Stability of the different Beclardia populations was carried out based on counts of juveniles and adults. Higher fertility rates and most stable populations were observed in the forests of Reunion Island (Bebours) and Madagascar (Ambohitanteley), whereas very low fruit set were observed in Mauritius, unless manual pollination was carried out. Microscopic analysis revealed the presence of pelotons of endomy-corrhiza during the early development of the seedlings , in vivo. Based on comparative studies among the different sites, pollinator limitation and absence of suitable hosts were the primary factors that led to the present decline in Mauritius. The high density of wild guava, Psidium cattleianum, which has slowly taken up most of the forest areas in Mauritius has affected the regenerating capacity of Beclardia mac-rostachya and the density of putative hosts of this orchid. GC-MS/MS analysis of nectar revealed α-D-glucopyranose to be the primary reward of the polli-nators and benzyl alcohol, methoxybenzyl alcohol and methoxy methyl phenol to be components floral fragrance .

Marine ecosystem management and conservation is facing growing challenges from multiple and cumulative stressors (Chapin et al., 2000). Marine ecosystems are threatened by global climate change pressures of such as increased sea surface temperatures, ocean acidification due to increased dissolution of one-quarter of atmospheric carbon dioxide (CO2) dissolution by world oceans annually (Figure 2) causing measurable declines in ocean pH (increase in H+ ions), carbonate ion concentration ([CO32−]) and saturation state (Le Quéré et al., 2015). This process, referred to as ocean acidification (OA), represents a major threat to marine ecosystems (McClanahan et al., 2011 see Figure 1).

Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal
fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km
away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion
(489 mM), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 lM and Mn = 78 lM). Chloride
depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than
~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of
around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with
an off-spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The
microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalthosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the
spreading axis, was characterized by high H2 concentration of 2.7 mM. The H2 enrichment was likely attributable
to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents.
Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced
the H2 enrichment. The quantitative cultivation test revealed that the microbial community associated with the
hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs
such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around
the H2-enriched hydrothermal fluid flows was also inferred from the 13C- and D-depleted signature of CH4 in the
collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013.

Concentrations of trace elements zinc, copper, nickel, chromium and heavy metals lead, mercury,
cadmium and arsenic were detected in the muscle tissues of four commercially edible fishes belonging
to the scombridae and related families including yellow fin tuna (Thunnus albacares), Dogtooth tuna
(Gymnosarda unicolor), Marlin (Makaira mazara) and the dolphin fish (Coryphaena hippuru) in the EEZ
(Exclusive Economic Zone) of Mauritius. The concentrations were within the range 1.34-10.03, 0.0-1.42,
0.23-0.89, 0.0-2.43, 0.0, 3.60-5.44, 0.03-0.13 and 0.03-0.07 mg/kg wet weight respectively for summer and
winter seasons. Inter-species variations with respect to elemental accumulations were not significantly
different as compared to seasonal variations for the accumulation of chromium, zinc and lead. Marlin
and Dorado caught during the summer season exceeded the authorised level of chromium in muscle
tissues according to international standards. A survey carried out among fish consumers in Mauritius
revealed that 80 % of the respondents were ignorant about heavy metal bio-accumulation.

Cadmium, lead and mercury and trace elements chromium, copper, nickel and zinc were tested in the muscle tissue of four commercial edible lethrinids fish species from different region of Mauritius. Skyemperor (Lethrinus mahsena) was collected from coastal regions as well as offshore regions (banks) for this study. Blackspot emperor (Lethrinus harak) and spangled
emperor (Lethrinus nebulosus) were also studied for their popularity in the fish market. Condition factor was calculated for each fish and the highest value obtained
was in Lethrinus mahsena collected from offshore regions (2.598 cm/g). Flame atomic absorption spectrometry was used to analyse copper, nickel and zinc while, graphite furnace technique was used for
cadmium, chromium and lead. Mercury levels were evaluated with the cold vapour technique and arsenic with the thermal hydride cell. The level of lead, mercury,
copper, nickel and zinc ranged from 0.0011- 0.0024 mg/L, 0.0016-0.0036 mg/L, 0.080- 0.389 mg/L, 0.566-1.192 mg/L and 0.219- 0.422 respectively in wet weight. Interspecies variations in levels of heavy metals and trace elements were observed for nickel and no ignificant variations occurred for mercury, lead and zinc. Concentrations of heavy metals and trace elements were all within the permissible level except for nickel. As per this study, the Food Act 1998 of Mauritius must be reviewed in order to  incorporate the Maximum Permissible Level for nickel.

The pulp extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses), commonly grown in Mauritius, were characterised in terms of their total soluble solids (TSS), titratable acidity (TA), polyphenol composition and vitamin C contents. Total phenolics ranged from 406.3±14 to 1694±19μgg−1 fresh weight (FW). Total flavonoids varied between 133±6 and

ABSTRACT Natural products as disease remedies have a history of near 5,000 years (India, China and Greece), and even today, in this advanced technological age, a revival of interest is being witnessed in the use of natural or plant-based therapeutic agents for the treatment of several pathological conditions. Citrus fruits have been utilised as a traditional medicine in India, China, Korea and Japan, and many studies have highlighted the various biological properties of their phytophenolics which are suggested to be responsible for the prevention of degene­rative diseases such as diabetes and cancer. With the background of comprehensive studies conducted on Mauritian citrus fruits, this chapter reviews some of the literature data on the phytophenolic contents, vitamin C composition and antioxidant functions of citrus extracts and emphasises on their potential applications in nutrition management programmes for diabetes and cancer chemoprevention.

Plant natural products have offered multiple bioactive phytochemicals in the past some of which are currently used as anticancer drugs. These include vinblastine, vincristine, the camptothecin derivatives, topotecan and irinotecan, etoposide, derived from epipodophyllotoxin, and paclitaxel (taxol). Madagascar and Small Indian Ocean Islands (Comoros, Mauritius, Reunion, Rodrigues, Seychelles) have inherited
a rich biodiversity with an immense and distinctive flora and fauna. The so called vinca Alkaloids isolated from the Madagascar Periwinkle Catharanthus roseus endemic to Madagascar island showcase the need to further screen other plants of Indian Ocean for their medicinal attributes including their anticancer potential. In this paper, we review the mode of action of common anticancer compounds and we target selected Mauritian endemic plant families to highlight their potential worth for in depth anticancer study in relation to their phytochemical profile

Purpose: To investigate the antimicrobial activity of crude and fractionated extracts of Biemna tubulosa
and Stylissa spp. thriving in Trou aux Biches lagoon, North East Mauritius.
Methods: Crude extracts (methanol: dichloromethane 1:1) and fractions of Biemna tubulosa and
Stylissa spp (hexane, ethyl acetate and butanol) were tested against some bacterial organisms,
namely, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis, using broth microdilution
assay. The extracts were screened for the presence of compounds that could be responsible for
bioactivity.
Results: Preliminary chemical screening revealed the presence of tannins, saponins, terpenes,
alkaloids and phenols. The hexane fraction of Stylissa spp. and the ethyl actetate and butanol extracts
of Biemna tubulosa were more active than the control antibiotic. Maximum antimicrobial activity was
noted for the butanol fraction of Biemna tubulosa with minimum inhibitory concentration (MIC) of 0.091
mg/ml against E. coli. The hexane soluble fraction of Stylissa spp. was more active with MIC of 0.125
mg/ml against S. aureus and E. coli and 0.250 mg/ml against E. faecalis.
Conclusion: The broad spectrum antibacterial activity of these sponges seemed to be due to the
presence of sesterterpenes and triterpenes, alkaloids and tannins detected in the extract fractions. This
is probably the first report on the antimicrobial activity of Biemna tubulosa and Stylissa spp. from
Mauritius waters.