Characterization of mutants of the chestnut blight fungus (<Emphasis Type="Italic">Cryphonectria parasitica</Emphasis>) with unusual hypovirus symptoms

The type virus of the family Hypoviridae, Cryphonectria hypovirus 1 strain EP713 (CHV1-EP713), infects Cryphonectria parasitica, the filamentous causal fungus of chestnut blight, and reduces its virulence. This pathosystem serves as a model to study fungus-mycovirus interactions. We previously developed a genetic screening protocol for host factors associated with symptom induction by CHV1-EP713 and its mutants. In the procedure the standard field fungal isolate EP155 was transformed by cDNA from a mild hypovirus mutant Cys(72), launching virus infection, and mutagenized by random plasmid insertion with pHygR conferring hygromycin resistance. We now report an extension of the study to characterize different mutant strains, with different phenotypes than their parental strain TCys(72)-1. TCys(72)-1 is moderately reduced in pigmentation and sporulation compared to the uninfected wild-type strain EP155. Mutants sfb1, sfb2 and k202 were characterized biologically and molecularly in comparison to the previously isolated mutant (namA) and the parental strain. These mutants harbored one (sfb1) or more copies (sfb2 and k202) of the mutagenic plasmid, pHygR. The three mutants had similar biological attributes; that is, vegetative growth rate, conidiation and virulence (assay on apples) was reduced on potato dextrose agar media, relative to the parental strain and pigmentation was the same or slightly increased. Interestingly, viral dsRNA accumulation levels were apparently unaltered in these mutants. The screening method was efficient for mining fungal mutants with unusual hypovirus symptoms. Further, characterization of the mutants provides interesting insights into symptom induction by the hypovirus.     

Household and homegarden characteristics in southwestern Bangladesh

Homegardens around the world often exhibit remarkable variation in composition and structure depending on the physiographic and climatic conditions of the area and a wide variety of household characteristics. This research investigated whether households’ contextual attributes have a quantitative and predictable relationship with homegarden vegetation structure from a total of 402 randomly selected households in southwestern Bangladesh. The central analytical tool to test the relationship between household characteristics and the homegarden vegetation structure was multiple regression. The moderate to low regression R ² values revealed that most household characteristics were not strong predictors of homegarden vegetation structure. Despite the weak explanatory power of the majority household characteristics, time spent and homestead size had the strongest relationship with species richness and income in a homegarden. Households being the main source of labor for a majority of households suggest that outside labor shortage would not influence homegarden vegetation structure. We suggest that women’s active participation in homegardening activities to reduce gender inequality in the family which will perhaps result in more diverse and economically viable homegarden. However, increasing population density and the concomitant fragmentation of landholdings to homesteads may create opportunity for homegarden promotion in Bangladesh. Our results of decreased species richness in the homegarden with improved roads and proximity to market support the general hypothesis of subsistence homegardens and did not reinforce the general fears of gradual decline in species richness due to a market economy. Household characteristics had no influence on the presence of IUCN Red Listed species in the homegarden, except for gender and education of the household head. However, most homegardeners were unaware about the status of red listed species, suggesting that occurrence of red listed species in homegardens was by chance. Thus, efforts to improve awareness and to save and conserve rare species from extirpation are needed.     

Traditional utilization of wild date palm （Phoenix sylvestris） in rural Bangladesh： an approach to sustainable biodiversity management

A study was conducted to explore the traditional utilization pattern and indigenous management practices of wild date palm （Phoenix sylvestris Roxb） in the rural agrarian regions of Bangladesh. A multistage sampling method with 10% intensity and a semi-structured questionnaire were used for the study. The farmers manage the palm mainly for sap production with which sugar based secondary goods are manufactured. The sap is either used fresh as drink or after some sort of processing as molasses and/or alcoholic beverage. Seven diversified sites support the palm as its habitat and most palms （20.40%） occur in orchards. Besides growing naturally, the palm is also established in orchards using the wildings as the staple planting material. Although the medium category farmers own most of the palms （33%）, a considerable portion （28.68%） of it is managed by the landless farmers, who earn a substantial livelihood from the palms. The farmers practice their own indigenous wisdom in every stage of the palm＇s maintenance from planting through tapping for sap collec- tion to the processing of products. If managed more scientifically on a sustainable basis with the collaboration of farmers＇ indigenou~ knowledge, this familiar palm could be able to support the rural economy of the country to a great extent. Side by side, it would also be able to contribute to the richness of biodiversity in the region.     

Aphidicidal activity of some indigenous plant extracts against bean aphid <Emphasis Type="Italic">Aphis </Emphasis><Emphasis Type="Italic">craccivora</Emphasis> Koch (Homoptera: Aphididae)

Aphidicidal activity of hot and cold water extracts of some indigenous plants, Azadirachta indica A. Juss (neem), Calotropis procera (Aiton) W.T. Aiton (akanda), Polygonum hydropiper L. (biskatali) and Ipomoea sepiaria J. Koenig ex Roxb. (bankalmi), were tested against the bean aphid, Aphis craccivora Koch. Hot water extract of P. hydropiper and A. indica was found to be the most effective (87.6–94.5 and 80.47–89.6% mortality respectively, P < 0.01) among all the extracts. Other hot and cold water extracts also appeared to be useful (59.5–87.5% mortality) as pesticides for A. craccivora. The highest yield (3.25 kg per plant) was obtained using hot water extract of P. hydropiper followed by hot water extract of A. indica (3.15 kg per plant). The lowest yield (0.32 kg per plant) was recorded from the control block. All the phytoproduct treatments had significantly (P < 0.01) better yield than the control block.     

Effect of Lherzolite on Chemical Fractions of Cd and Zn and their Uptake by Plants in Contaminated Soil

Immobilizing materials such as lherzolite could reduce metal bioavailability but the effectiveness of lherzolite on the extractability and bioavailability of cadmium (Cd) and zinc (Zn) is rarely investigated. We conducted a greenhouse experiment to investigate the effect of 5% application of lherzolite to a contaminated soil on the chemical fractionation of Cd and Zn and their uptake by radish (Raphanus sativus L.) and Japanese mustard spinach (Brassica rapa L. var. perviridis). Both plants were grown in a highly contaminated (with Cd and Zn) sandy loam soil. Plants were cultivated consecutively three times in the same pots. After the third cultivation, soil samples were collected and analyzed by sequential extraction procedure into five operationally defined fractions (F1—exchangeable, F2—carbonate-bound, F3—oxides-bound, F4—bound with organic matter, and F5—residual). Addition of lherzolite to soil decreased 50% of exchangeable (F1) Cd but it increased the carbonate (F2), oxide (F3), and organic (F4) fraction Cd. For Zn, application of lherzolite resulted into the reduction of both F1 (87%) and F2 (33%) fractions but it increased the F3, F4, and F5 fractions. The reduction in exchangeable fraction of Cd and Zn in the soil resulted in higher plant growth and lower concentrations of both Cd (64% to 92%) and Zn (78% to 99%) in plant tissues of both plant species grown. We may thus conclude that application of lherzolite resulted into lower availability of these metals in the soil leading to lower uptake of Cd and Zn by plant roots, lower toxicity, and ultimately higher plant growth.     

Sawfish exploitation and status in Bangladesh

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Characterization of plant and animal based natural fibers reinforced polypropylene composites and their comparative study

Natural fibers are largely divided into two categories depending on their origin: plant based and animal based. Plant based natural jute fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated by compression molding. Bending strength (BS), bending modulus (BM), tensile strength (TS), Young’s modulus (YM), and impact strength (IS) of the composites were found 44.2 MPa, 2200 MPa, 41.3 MPa, 750 MPa and 12 kJ/m², respectively. Animal based natural B. mori silk fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated in the same way and the mechanical properties were compared over the silk based composites. TS, YM, BS, BM, IS of silk fiber reinforced polypropylene composites were found 55.6 MPa, 760 MPa, 57.1 MPa, 3320 MPa and 17 kJ/m² respectively. Degradation of composites in soil was measured upto twelve weeks. It was found that plant based jute fiber/PP composite losses its strength more than animal based silk fiber/PP composite for the same period of time. The comparative study makes it clear that mechanical properties of silk/PP composites are greater than those values of jute/PP composites. But jute/PP composites are more degradable than silk/PP composites i.e., silk/PP composites retain their strength for a longer period than jute/PP composites.     

Vertical transmission of sublethal granulovirus infection in the tobacco caterpillar <Emphasis Type="Italic">Spodoptera litura</Emphasis>

Larvae that survived sublethal infection of Spodoptera litura granulovirus (SlGV) as 4th and 5th instars led to an increase in the larval period of treated larvae when compared with control. While pupal period and pupal weight remained unaffected, a significant alteration in sex ratio was observed. Although survivor moths could mate successfully, there was a significant reduction in the proportion of ovipositing females in treated larvae as compared with control. A significant reduction in fecundity of moths emerging from treated larvae was also noticed, but the egg viability was never influenced by the treatment. However, there was a significant increase in progeny mortality in treated larvae over control. The offspring mortality in survivors increased up to three subsequent generations but not thereafter. Hence, repeated field applications of inoculum are required. The implication of the present findings in terms of reduced fecundity coupled with increased larval development indicates that vertical transmission can lead to increased virus dispersal, both of which would reduce the host's innate capacity for population increase. This is particularly important in S. litura, which is a migratory species and occurs sporadically in a particular agro-ecosystem.     

Stochastic modeling of production risk and technical efficiency of Thai koi (Anabas testudineus) farming in Northern Bangladesh

Thai koi is one of the high commercially valued farm fishes which have expanded tremendously in the northern part of Bangladesh. However, despite its impressive growth in the initial years, output of the industry is highly volatile across different years and farms. This research, following the Just and Pope framework, has made use of Kumbhakar’s (2002 Kumbhakar, S.C. (2002) Specification and estimation of production risk, risk preferences, and technical efficiency. American Journal of Agricultural Economics, 84, 8–22.[Crossref], [Web of Science ®] , [Google Scholar]) extended stochastic frontier model (SFM) to estimate production risk and technical efficiency (TE) in Thai koi farming. Results show that feed is the most important input significantly influencing production. Zeolite and pesticide appear to be risk-reducing, while fingerlings, labor, feed and salt turn out to be risk-increasing inputs. The inefficiency model indicates that labor and pond area significantly reduce the technical inefficiency. Feed, fingerling and lime also act as TE-improving factors. Education of farmers improves TE, while experience, training and frequency of water change do not impact the TE. The mean TE scores are 0.73 and 0.96 for the flexible risk estimate and conventional SFM estimates, respectively. TE values appear to become exaggerated when production risk is excluded from the model. SFM recognizes that risk is involved in Thai koi farming that causes lower TE.