Climate Change Impacts on a Tropical Fishery Ecosystem: Implications and Societal Responses

The present study aimed to map out the current threats and anticipated impacts of climate change on the most important hilsa shad (Tenualosa ilisha) fishery and the associated fishing communities based on fieldwork in six coastal fishing communities. To collect empirical data, individual interviews, focus group discussions, oral history, and key informant interviews were conducted. To supplement the empirical findings, time-series data of cyclones and sea-borne depressions in the Bay of Bengal were also analyzed. Analysis of secondary data regarding climate change-induced events and regional studies suggested that the biophysical conditions of the Bay of Bengal are likely to be aggravated in the future, potentially causing more frequent extreme events and affecting the livelihoods of coastal fishing communities in Bangladesh. The fisher respondents revealed that the main target hilsa shad fishery is particularly vulnerable to climate change in terms of alterations to migration patterns and breeding and growth performance. The fishers reported constant climate-related risks because they live in seafront locations, exposed to extreme events, and their occupation entails risky sea fishing. Fishers claimed that they often need return to the coast due to unsuitable weather conditions related to cyclones and frequent tropical depressions, which can cause financial losses or even causalities. Such events negatively affect fishers’ livelihoods, and wellbeing. To cope with the impacts of climate change the fishers have adopted various strategies at both sea fishing and household levels. However, these strategies only support the fishers in terms of immediate survival; they are not enough for long-term resilience. To improve the resilience of the hilsa fishers, the study argues for the implementation the Small-Scale Fisheries Guidelines (SSF Guidelines), which call for longer-term development goals, including in the immediate relief phase, and rehabilitation, reconstruction, and recovery to reduce vulnerabilities to climate and anthropogenic risks

Systematics, ecology and plant associations of Australian species of the genus metarhizium

Fungi of the genus Metarhizium (Family:Clavicipitaceae, Order: Hypocreales) can be both pathogens of insects and form mutualistic relationship with plants. This research collected and described Metarhizium isolates from agricultural crops, grasslands and forests soils Queensland, Australia and identified crop, soil factors and agricultural management that may affect the distribution of the species. It identified two new taxa of the genus and identified the presence of several species known to occur internationally. There were specific associations of taxa with crop and ecotype. The two new Australian taxa also colonized the roots of maize, a monocot, in contrast to other taxa which typically favor eudicots (legumes). It also identified the potential role of the plant hormone strigolactone in fungal colonization of the plant root. The work identified the potential to select fungal taxa in order to improve crop production through application of these fungi as root inocula

Influence of the plant hormone strigolactone on conidium germination and colonisation of plant roots by Metarhizium anisopliae

Hypocrealean fungi of the genus Metarhizium are known rhizospheric-competent symbionts that support increased plant growth and development. However, the establishment of inocula in the rhizosphere is typically low. We investigated the role of plant: fungal signals and specifically of the plant hormone strigolactone in colonisation of pea plant roots by M. anisopliae. Germination of conidiospores in root exudate and colonisation of the root by M. anisopliae were estimated on wild variety pea (Pisum sativum L. cv Torsdag) and the mutants, rms 5-3: strigolactone-deficient and rms 4-1: strigolactone-overproducing mutants. Condiospore germination was significantly lower in root exudates from the strigolactone-deficient pea (rms 5-3) than in exudates from wild and strigolactone -overproducing (rms 4-1) mutant plants. Colonisation of root segments was higher in wild and strigolactone -overproducing (rms 4-1) mutant plants than the strigolactone-deficient (rms 5-3) plants. This is the first report indicating that plant strigolactone increases both conidiospore germination and colonisation of the root by species of Metarhizium

DNA Fingerprinting and Genotyping of Cotton Varieties Using SSR Markers

DNA fingerprinting and genetic diversity analysis helps direct selective breeding and conservation of plant species. Since simple sequence repeats (SSR) markers are co-dominant, they can predict level of genetic diversity and thereby protect plant genetic resources of a region. Keeping the aforesaid rationale in mind, we worked on molecular characterization of eight cotton varieties in Bangladesh using simple sequence repeat (SSR) or microsatellite DNA markers. All the three microsatellite DNA markers were found to be polymorphic, extracting a total of eight alleles with an average of 2.67 alleles per locus in the present study. Allele sizes were as 149-155 bp, 178-198 bp and 140-202 bp for the loci BNL1551, BNL1721 and BNL2960, respectively. Polymorphism Information Content (PIC) values were ranged from 0.469 to 0.531. UPGMA dendrogram separated 8 varieties of cotton into two clusters. One cluster contained six varieties CB-1, CB-2, CB-3, CB-7, CB-9 and CB-10 while other two varieties CB-5 and HC 1 formed another cluster. The findings of this study would provide a useful guide for selecting specific germplasm with distinct genetic background for diversifying cotton breeding program in Bangladesh

Understanding the political ecology of forced migration and deforestation through a multi-algorithm classification approach: the case of Rohingya displacement in the southeastern border region of Bangladesh

Compared with numerous existing forced migration scenarios across the globe, migration from Myanmar to Bangladesh through southeastern border region is unique at least for three reasons – (i) very large number of migrants have been displaced to (ii) a very small area in (iii) a relatively short period of time, creating an obvious cumulative impact on forest cover area of the host country. Therefore, this study aims to analyze the dynamics of refugee migration and deforestation in Bangladesh. Satellite images of Landsat-5 & 8 and Sentinel-2 were classified via four different classification algorithms (SVM, Random Forest, CART, and Max Entropy) to measure major land use and land cover changes, namely, (i) dense forest, (ii) sparse forest, (iii) open area, and (iv) settlement from 1988 to 2018. The analysis revealed a declining trend of dense forest area, majority of which took place from 2016 to 2018 triggered by Rohingya migration. As a whole, the dense forest cover has been effectively halved (8531 ha in 2016 to 4498 ha in 2018) in the span of just two years while refugee settlement has increased nine-folds (271 ha in 2016 to 2679 ha in 2018). Aggregated and indisputable conclusion has been derived indicating that forced Rohingya migration and deforestation are indeed positively correlated

Integrated management of Fusarium wilt of chickpea (Cicer arietinum L.) caused by Fusarium oxysporum f. sp. ciceris with microbial antagonist, botanical extract sp. ciceris with microbial antagonist, botanical extract

The present study was carried out to assess the efficacy of an integrated management strategy for Fusarium wilt of chickpea that combined the use of microbial antagonist, botanical extract and fungicide. Before setting the experiment in field micro plots, a series of in vitro and in vivo experiments were conducted to select a virulent isolate of F. oxysporum f. sp. ciceris, an effective antagonistic isolate of Trichoderma harzianum, a fungitoxic botanical extract and an appropriate fungicide. The isolate FS1 of F. oxysporum f. sp. ciceris appeared to be most virulent to chickpea cultivar BU-Chola-1 and selected as test pathogen. Among the 20 isolates screened, T. harzianum isolate T-75 showed the highest (75.89%) inhibition of the radial growth of F. oxysporum f. sp. ciceris in dual culture assay on PDA. Absolute inhibition (100.00%) of colony growth of F. oxysporum f. sp. ciceris was observed where fungicide Provax-200 at 100 ppm was used. Azadirachta indica leaf extract gave maximum inhibition (55.19%) of radial growth of F. oxysporum f. sp. ciceris at all concentrations. The integration of soil treatment with T. harzianum isolate T-75 and Az. indica leaf extract and seed treatment with Provax-200 appeared to be significantly superior in reducing Fusarium wilt and in improving seed yield of chickpea compared to any single or dual application of them in the field. The results of this study exhibit the importance of integrating selective microbial antagonist, botanical extract and fungicide to achieve appropriate management of Fusarium wilt and increase of seed yield in chickpea in Bangladesh.Keywords: Integrated management, Fusarium wilt, Fusarium oxysporum f. sp. ciceris, chickpea (Cicer arietinum L.), antagonists, botanicals, fungicides.African Journal of Biotechnology Vol. 12(29), pp. 4699-470

Biocontrol potential of native isolates of Beauveria bassiana against cotton leafworm Spodoptera litura (Fabricius)

Abstract The entomopathogenic fungus (EPF), Beauveria bassiana, is reported as the most potent biological control agent against a wide range of insect families. This study aimed to isolate and characterize the native B. bassiana from various soil habitats in Bangladesh and to evaluate the bio-efficacy of these isolates against an important vegetable insect pest, Spodoptera litura. Seven isolates from Bangladeshi soils were characterized as B. bassiana using genomic analysis. Among the isolates, TGS2.3 showed the highest mortality rate (82%) against the 2nd instar larvae of S. litura at 7 days after treatment (DAT). This isolate was further bioassayed against different stages of S. litura and found that TGS2.3 induced 81, 57, 94, 84, 75, 65, and 57% overall mortality at egg, neonatal 1st, 2nd, 3rd, 4th, and 5th instar larvae, respectively, over 7 DAT. Interestingly, treatment with B. bassiana isolate TGS2.3 resulted in pupal and adult deformities as well as decreased adult emergence of S. litura. Taken together, our results suggest that a native isolate of B. bassiana TGS2.3 is a potential biocontrol agent against the destructive insect pest S. litura. However, further studies are needed to evaluate the bio-efficacy of this promising native isolate in planta and field conditions

Pseudomonas and Burkholderia inhibit growth and asexual development of Phytophthora capsici

The objective of this study was to isolate and characterize antagonistic rhizobacteria from chili against a notorious phytopathogen Phytophthora capsici. Among the 48 bacteria isolated, BTLbbc-02, BTLbbc-03, and BTLbbc-05 were selected based on their inhibitory activity against P. capsici. They were tentatively identified as Burkholderia metallica BTLbbc-02, Burkholderia cepacia BTLbbc-03, and Pseudomonas aeruginosa BTLbbc-05, respectively, based on their 16S rRNA gene sequencing. All inhibited the growth of P. capsici at varying levels by inducing characteristic morphological alterations of P. capsici hyphae. The cell-free culture supernatant of all three isolates impaired motility (up to 100%) and caused lysis (up to 50%) of the halted zoospores. Bioassays revealed that Pseudomonas sp. had higher antagonism and zoospore motility-inhibitory effects against P. capsici compared with two other isolates, Burkholderia spp. and B. metallica, which caused vacuolation in mycelium. All three bacteria suppressed sporangium formation and zoosporogenesis of P. capsici, and improved the seed germination and growth of cucumber. Our findings suggest that epiphytic bacteria, B. metallica, B. cepacia, and P. aeruginosa, could be used as potential biocontrol agents against P. capsici. A further study is required to ensure conformity with the existing regulations for soil, plant, and human health

Sphingomonas panaciterrae PB20 increases growth, photosynthetic pigments, antioxidants, and mineral nutrient contents in spinach (Spinacia oleracea L.)

Plant growth promoting rhizobacteria (PGPR) have been intensively investigated in agricultural crops for decades. Nevertheless, little information is available on the application of Sphingomonas spp. as a PGPR particularly in vegetables, despite of potential plant growth promoting traits of this group. This study investigated the role of Sphingomonas panaciterrae (PB20) on growth and nutritional profile of spinach applied through seed priming (SP), soil drenching (SD), foliar application (FA), and bacterial culture filtrate foliar (BCF) applications. The results showed that, depending on different methods of application, PB20 significantly increased plant height (19.57–65.65 %), fresh weight (7.26–37.41 %), total chlorophyll (71.14–192.54 %), carotenoid (67.10–211.67 %) antioxidant (55.99–207.04), vitamin C (8.1–94.6 %) and protein content (6.7–21.5 %) compared to control in the edible part of spinach. Among the mineral nutrients, root nitrogen (N) showed greater response to bacterial application (18.65%–46.15 % increase over control) than shoot nitrogen (6.70%–21.52 % increased over control). Likewise, in all methods of application, phosphorus (P) content showed significant increase over control both in root (42.79–78.48 %) and in shoot (3.57–27.0 %). Seed priming and foliar application of PB20 increased the shoot calcium (Ca) content compared to control. BCF foliar application yielded maximum magnesium (Mg), iron (Fe) and zinc (Zn) in shoot. However, seed priming resulted in maximum Fe in root. Overall, seed priming outperformed in growth, vitamin C, antioxidants, N and P uptake, while BCF foliar application resulted in better uptake of several nutrients. Multivariate analysis validated the positive association of most of the growth parameters with SP while several nutrients with FA and BCF. Based on the findings it is evident that this rhizobacteria PB20 has the potentiality to be applied as a biofertilizer to produce nutrient-enriched spinach with an improved yield. Farmers can conveniently incorporate PR20 through seed priming before planting of spinach, with additional benefits through foliar spray

Effect of Metarhizium anisopliae (MetA1) on growth enhancement and antioxidative defense mechanism against Rhizoctonia root rot in okra

Rhizoctonia solani is an important necrotrophic pathogenic fungus that causes okra root disease and results in severe yield reduction. Many biocontrol agents are being studied with the intent of improving plant growth and defense systems and reducing crop loss by preventing fungal infections. Recently, a member of the Hypocrealean family, Metarhizium anisopliae, has been reported for insect pathogenicity, endophytism, plant growth promotion, and antifungal potentialities. This research investigated the role of M. anisopliae (MetA1) in growth promotion and root disease suppression in okra. The antagonism against R. solani and the plant growth promotion traits of MetA1 were tested in vitro. The effects of endophytic MetA1 on promoting plant growth and disease suppression were assessed in planta. Dual culture and cell-free culture filtrate assays showed antagonistic activity against R. solani by MetA1. Some plant growth promotion traits, such as phosphate solubilization and catalase activity were also exhibited by MetA1. Seed primed with MetA1 increased the shoot, root, leaves, chlorophyll content, and biomass content compared to control okra plants. The plants challenged with R. solani showed the highest hydrogen peroxide (H2O2) and lipid peroxidation (MDA) contents in the leaves of okra. Whereas MetA1 applied plants showed a reduction of H2O2 and MDA by 5.21 and 14.96%, respectively, under pathogen-inoculated conditions by increasing antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), glutathione S-transferase (GST), and ascorbate peroxidase (APX), by 30.11, 10.19, 5.62, and 5.06%, respectively. Moreover, MetA1 increased soluble sugars, carbohydrates, proline, and secondary metabolites, viz., phenol and flavonoid contents in okra resulting in a better osmotic adjustment of diseases infecting plants. MetA1 reduced disease incidence by 58.33% at 15 DAI compared to the R. solani inoculated plant. The results revealed that MetA1 improved plant growth, elevated the plant defense system, and suppressed root diseases caused by R. solani. Thus, MetA1 was found to be an effective candidate for the biological control program