Somatic embryogenesis in strawberry (<Emphasis Type="Italic">Fragaria</Emphasis> sp.) through callus culture

Somatic embryogenesis was achieved from callus from leaf and nodal segments of strawberry clone pbgel-2000. The highest percent of cultures with somatic embryos was achieved on MS medium supplemented with 1.0 mg/l 2,4-D, 0.5 mg/l BAP and 50% proline. Darkness was the best condition for incubation with daily light periods over 6 h reducing the frequency of embryogenesis. Regenerated plants (90–95%) were successfully transferred to soil, showed normal morphology and produced fruit four months after planting.     

Human–Tiger Conflict in Context: Risks to Lives and Livelihoods in the Bangladesh Sundarbans

People’s perceptions of the risk posed by wild animals to human lives and/or livelihoods can influence the rate at which people intentionally kill these species. Consequently, human–wildlife conflict (HWC) management strategies may benefit from the inclusion of actions which reduce risk perceptions. This study uses Participatory Risk Mapping (PRM) and semi-structured interviews to explore local perceptions and the wider socio-economic context of human–tiger conflict (HTC) in the Bangladesh Sundarbans area. Of the 24 locally-relevant problems identified by the PRM process, tigers were the only problem to be cited by >50 % of respondents. The ‘tiger problem’ was also perceived by villagers to be of relatively high severity. Negative perceptions of tigers in the Sundarbans communities are exacerbated by other locally-experienced poverty-related problems, as well cyclones, floods and soil erosion. Interactions between the problems experienced by villagers, including HTC, result in a complex ‘risk web’ which detrimentally affects lives and livelihoods and ultimately perpetuates poverty levels in the Sundarbans communities. This research demonstrates that PRM and in-depth, qualitative research can enhance understanding of the perceived magnitude and wider socio-economic context of risks from wildlife and aid the identification of risk perception management actions which may help to reduce the number of animals killed by people.     

Accumulation of arsenic in soil and rice under wetland condition in Bangladesh

Shallow tube well (STW) water, often contaminated with arsenic (As), is used extensively in Bangladesh for irrigating rice fields in the dry season, leading to potential As accumulation in soils. In the current study the consequences of arsenic from irrigation water and direct surface (0–15 cm) soil application were studied under field conditions with wetland rice culture over 2 years. Twenty PVC cylinders (30-cm length and 30-cm diameter) were installed in field plots to evaluate the mobility and vertical distribution of soil As, As mass balance, and the resulting influences on rice yield and plant-As concentration in Boro (dry season) and transplanted (T.) Aman (wet season) rice over the 2-year growth cycle. Treatments included irrigation-water As concentrations of 0, 1 and 2 mg L^?1 (Boro season only) and soil-As concentrations of 10 and 20 mg kg^?1. Following the 2-year cropping sequence the major portion (39.3–47.6%) of the applied arsenic was retained within the rooting zone at 0–15 cm depth, with 14.7–19.5% of the total applied As at the 5–10 cm and 10–15 cm soil depths compared to 1.3–3.6% at the 35–40 cm soil depth. These results indicate the relatively low mobility of applied As and the likely continued detrimental accumulation of As within the rooting zone. Arsenic addition in either irrigation water or as soil-applied As resulted in yield reductions from 21 to 74 % in Boro rice and 8 to 80 % in T. Aman rice, the latter indicating the strong residual effect of As on subsequent crops. The As concentrations in rice grain (0.22 to 0.81 µg g^?1), straw (2.64 to 12.52 µg g^?1) and husk (1.20 to 2.48 µg g^?1) increased with increasing addition of As. These results indicate the detrimental impacts of continued long-term irrigation with As-contaminated water on agricultural sustainability, food security and food quality in Bangladesh. A critical need exists for the development of crop and water management strategies to minimize potential As hazard in wetland rice production.     

Chitinase of Bacillus licheniformis from oyster shell as a probe to detect chitin in marine shells

Bacillus licheniformis CBFOS-03 is a chitinase producing bacteria isolated from oyster (Crassostrea gigas) shell waste. We have cloned and expressed the chi18B gene of B. licheniformis CBFOS-03, which encodes a glycohydrolase family 18 chitinase (GH18). Chi18B is a predicted 598 amino acid protein that consists of a catalytic domain (GH18), a fibronectin type III domain (Fn3), and a chitin binding domain (CBD). Purified Chi18B showed optimum chitinase activity at pH 9 and 55 °C, and activity was stimulated with 25 mM Mn²⁺. In kinetic analysis, Chi18B showed Km values of 9.07?±?0.65 μM and 129.27?±?0.38 μM with the substrates 4-methylumbelliferyl-N-N′-diacetylchitobiose and α-chitin, respectively. Studies of C-terminal deletion constructs revealed that the GH18 domain with one amino acid in C-terminal region was sufficient for chitinase activity; however, fusions of full length and CBD-deleted constructs to green florescent protein (GFP) and yellow florescent protein (YFP) suggest that the C-terminus is supposedly important in binding to shell powder. Full length Chi18B with GFP showed green fluorescence with oyster shell powder, but GH18+Fn3 with GFP did not. Similarly, full length Chi18B with YFP showed yellow fluorescence with clam (Chamelea gallina) shell and disk abalone (Haliotis discus) shell powder, but GH18+Fn3 with YFP construct did not. So, the CBD domain of Chi18B appears to play an important role in binding of oyster and other marine shells. It is likely to be used as a probe to identify the presence of chitin in marine shells like oyster shell, clam shell, and disk abalone shell using fusions of Chi18B with fluorescent proteins.     

Fatal Outbreak from Consuming Xanthium strumarium Seedlings during Time of Food Scarcity in Northeastern Bangladesh

Background

An outbreak characterized by vomiting and rapid progression to unconsciousness and death was reported in Sylhet Distrct in northeastern Bangladesh following destructive monsoon floods in November 2007.

Methods and Findings

We identified cases presenting to local hospitals and described their clinical signs and symptoms. We interviewed patients and their families to collect illness histories and generate hypotheses about exposures associated with disease. An epidemiological study was conducted in two outbreak villages to investigate risk factors for developing illness. 76 patients were identified from 9 villages; 25% (19/76) died. Common presenting symptoms included vomiting, elevated liver enzymes, and altered mental status. In-depth interviews with 33 cases revealed that 31 (94%) had consumed ghagra shak, an uncultivated plant, in the hours before illness onset. Ghagra shak was consumed as a main meal by villagers due to inaccessibility of other foods following destructive monsoon flooding and rises in global food prices. Persons who ate this plant were 34.2 times more likely (95% CI 10.2 to 115.8, p-value<0.000) than others to develop vomiting and unconsciousness during the outbreak in our multivariate model. Ghagra shak is the local name for Xanthium strumarium, or common cocklebur.

Conclusions

The consumption of Xanthium strumarium seedlings in large quantities, due to inaccessibility of other foods, caused this outbreak. The toxic chemical in the plant, carboxyatratyloside, has been previously described and eating X. strumarium seeds and seedlings has been associated with fatalities in humans and livestock. Unless people are able to meet their nutritional requirements with safe foods, they will continue to be at risk for poor health outcomes beyond undernutrition.