Relationships of overstory trees and shrubs with forage species portray ecosystem service interactions in smallholder fallows

Interactions among ecosystem services are increasingly perceived as important to ecosystem service delivery. Synergies and trade-offs among ecosystem services arise through direct ecological interactions or indirectly through correlated responses to other factors. To investigate whether and how interactions of overstory trees and shrubs with livestock forage species growing beneath generate ecosystem service interactions, overstory and forage species were examined in smallholder fallows in western Kenya. In 18 grazed and 21 improved fallows, we estimated biomass and quantified soil properties. We assessed whether the overstory reduces forage biomass and quality through competition, and whether overstory niche complementarity ameliorates competition or enhances facilitation. In improved fallows, forage biomass declined with overstory biomass, indicating competition and a wood-forage trade-off. In grazed fallows, biomass of higher quality forage species increased with overstory biomass, indicating a synergy, likely indirect. Niche complementarity, quantified as taxonomic and functional diversity, did not appear influential. Forage quality was not associated with overstory characteristics, but declined with grazing intensity. The contrasting relationships between overstory and forage species among fallow types appear ultimately attributable to the presence and intensity of grazing and the dense overstory in improved fallows.     

The functions of biological diversity in an age of extinction

Ecosystems worldwide are rapidly losing taxonomic, phylogenetic, genetic, and functional diversity as a result of human appropriation of natural resources, modification of habitats and climate, and the spread of pathogenic, exotic, and domestic plants and animals. Twenty years of intense theoretical and empirical research have shown that such biotic impoverishment can markedly alter the biogeochemical and dynamic properties of ecosystems, but frontiers remain in linking this research to the complexity of wild nature, and in applying it to pressing environmental issues such as food, water, energy, and biosecurity. The question before us is whether these advances can take us beyond merely invoking the precautionary principle of conserving biodiversity to a predictive science that informs practical and specific solutions to mitigate and adapt to its loss.     

Heat stress and plant development: role of sulphur metabolites and management strategies

Temperature plays a crucial role in plants development whereas a sudden rise may cause severe consequences. Heat stress impairs plant growth, photosynthesis, pollen development and reproduction. The plant photosynthetic efficiency is mainly reduced by the over production of reactive oxygen species, denaturation of heat shock proteins and alteration in many enzymes activities. Unlike drought stress, plants have developed a very few mechanisms to encounter heat stress problem. Recently, the use of nutrients such as sulphur has emerged as one of the efficient methods to enhance plant tolerance against high temperature stress. The mechanistic understanding of sulphur-based strategies could be very helpful to sustain plant development and global food supplies in future hotter climates. The present review mainly focuses on (1) high temperature induced changes in plant functions, (2) possible roles of sulphur metabolites in heat stress tolerance and (3) possibilities of using sulphur as a management strategy. Moreover, the review consolidates the future research needs that must focus on (i) heat tolerant germplasm screening; (ii) sulphur dose optimisation, application method and crop growth stages response; (iii) finding of sulphur induced heat tolerance mechanisms and (iv) the use of omic approaches to discover sulphur metabolites role in heat stress tolerance.     

Structure, diversity, and regeneration potential of Monotheca buxifolia (Falc.) A. DC. dominated forests of Lower Dir District, Pakistan

This study reports on the multivariate analysis of the vegetation of Hindukush Range in Pakistan, concentrating on the structure and regeneration potential of Monotheca buxifolia and associated tree species. Twenty stands at different locations in the Dir District of the Hindukush Range in Pakistan were chosen for the study. A point centered quarter method for trees and 5m × 5m size quadrats were used for the sampling of understorey vegetation, including shrubs, seedlings, and saplings, respectively. The underlying group structure in vegetation was exposed by an agglomerative clustering technique, while major trends were disclosed by DCA ordination. Size class structure and regeneration potential of M. buxifolia and associated tree species were also examined, which reflects the future trend of species and, consequently, the forests where they dominate. The relationships between environmental factors and vegetation were investigated.     

Impacts of abiotic factors on population fluctuation of insect fauna of Vigna radiata and Tetranychus urticae Koch in Sindh, Pakistan

Effect of temperature and relative humidity on population dynamics of insect pests of mung bean was studied during mung bean growing season of 2005. Insect pests included thrips (Thrips tabaci Lind.) and field cricket (Gryllus assimilis) and one arachnid pest mite (Tetranychus urticae Koch). Results revealed that the maximum population of thrips and mites was observed on August 23, 2005 with 1.537±0.031 per leaf and July 6, 2005 with 3.271±0.09 per leaf, respectively. The population of field cricket differed significantly during crop season and reached its peak during the initial stage of crop growth on June 14, 2005, i.e., 0.873±0.014 per plant at the temperature and relative humidity of 32°C and 54%, respectively, while the minimum population was noted on August, i.e., 0.710±0.010 per plant. Present studies conclusively document the correlation of weather factors and insect pest population. Temperature had a negative and significant correlation with thrips (r = −0.860) and a positive and significant correlation with mites (r = 0.606) and field cricket (r = 0.439). However, the relative humidity displayed a positive and significant correlation with thrips (r = 0.569), a negative non-significant correlation with mites (r = −0.313), and a significant negative correlation with field cricket (r = −0.770).     

An analysis of the resistance of Gossypium arboreum to cotton leaf curl disease by grafting

Cotton leaf curl disease (CLCuD) is a serious constraint to cotton production across Pakistan and north-western India. In the Punjab province of Pakistan at this time CLCuD is associated with one virus, Cotton leaf curl Burewala virus (CLCuBuV), and its associated betasatellite, Cotton leaf curl Multan betasatellite (CLCuMuB). Although some resistance to the virus complex causing CLCuD has been identified in Gossypium hirsutum, this has in the past proven not to be durable. At this time no commercial lines with strong resistance (immunity) to CLCuD are available. Although the cotton fibre produced by Gossypium arboreum is not of the quality required by processors, the species has a number of desirable characters, including resistance to a number of abiotic and biotic stresses, including CLCuD. For this reason there have been efforts to introgress CLCuD-resistance from G. arboreum into G. hirsutum. However, the nature of the resistance of G. arboreum to the viruses causing CLCuD remains unknown. An initial analysis of the resistance was herein conducted by graft inoculation. Graft inoculation of G. arboreum genotype Ravi with scions from severely infected G. hirsutum genotype CIM 496 plants showed that G. arboreum is able to support virus/betasatellite replication and long-distance spread. However, following grafting, only a small number of leaves developing at the time of grafting became mildly symptomatic and symptomatic tissue contained low amounts of virus/satellite DNA, as detected by Southern blot hybridisation; significantly less than the levels seen in G. hirsutum. The symptoms did not spread to the young upper leaves of graft inoculated plants, which contained DNA levels that could only be detected by polymerase chain reaction (PCR) or PCR following an initial amplification by rolling circle amplification–indicating very low DNA levels. The results showed that the resistance of G. arboreum to the virus complex causing CLCuD likely does not involve a mechanism that interferes with delivery of virus by the insect vector. Rather the resistance appears to be due to poor virus replication and possibly interference in short distance (cell-to-cell) spread.     

ORIGINAL ARTICLE: Effect of the level of cholecalciferol supplementation of broiler diets on the performance and tibial dyschondroplasia

A study was conducted to evaluate four different cholecalciferol levels (NRC; modified), using diets supplemented with 200 (control), 1500, 2500 or 3500 IU/kg of cholecalciferol (VIT‐D3). Each treatment was assigned to 3 pens of 17 broiler chicks of a commercial strain grown in an open‐sided house with sidewall curtains. At 21and 42 days, BW and feed conversion (FCR) were determined. At 42 days, five birds per pen were slaughtered to evaluate tibia and toe ash of the right leg, and incidence and severity of tibial dyschondroplasia (TD) of the left tibia and also measured dressing percentage and breast meat yield. Serum calcium and phosphorus concentrations were also determined. Haemagglutination inhibition antibody titre against Newcastle disease virus and lymphoid organs weight/body weight ratio were also determined. At both 21 and 42 days, the BW of birds fed 1500 IU/kg to 3500 IU/kg of VIT‐D3 was significantly greater than birds fed 200 IU/kg. Similarly, better FCR was observed in birds those fed diets of high level of VIT‐D3. No significant difference was observed for mortality at any age. Better dressing percentage and breast meat yield were noted in birds fed diets containing 2500 or 3500 IU/kg VIT‐D3. Both tibia and toe ash contents were increased (p < 0.05) progressively with increased concentrations of cholecalciferol in feed. The incidence of TD (percentage of birds having TD scores greater than zero) was significantly (p < 0.05) influenced by level of 3500 IU VIT‐D3/kg at 42 days. The severity of TD in birds fed diets containing 200 IU/kg VIT‐D3 was apparently higher than birds fed diets with higher levels of VIT‐D3. Concentrations of calcium and phosphorus minerals in the serum increased progressively with the high level of VIT‐D3 supplementation to birds at both 21 and 42 days of age. Feeding levels of 1500 or 3500 IU of vitamin D3 did positively affect the immune system within the parameters measured. It may be concluded that performance, bone mineralization, blood chemistry and immunity against disease in broilers could be maintained when supplementing high level of VIT‐D3 incorporated in broiler diets.     

Setting the net lower: A potential low-cost mitigation method to reduce cetacean bycatch in drift gillnet fisheries

1. Bycatch is the most significant threat to marine megafauna (sea turtles, marine mammals, elasmobranchs, seabirds) worldwide, and the leading cause of the decline of several cetacean species. The bycatch issue in the Indian Ocean is poorly understood, but high bycatch levels in gillnet fisheries have been documented for the past two decades, in both small-scale and semi-industrial fisheries. Unfortunately, methods to reduce bycatch are often unavailable, financially non-viable or socially unacceptable to fishermen.
2. Using a network of trained boat captains in the tuna drift gillnet fishery in the Arabian Sea, targeted catch and bycatch data were collected from 2013 to 2017 off the coast of Pakistan (northern Indian Ocean). Two fishing methods using multifilament gillnets were used: surface deployment and subsurface deployment (i.e. headline of net set below 2 m depth).
3. Predicted catch rates for targeted species did not differ significantly between the two fishing practices, although a drop in tuna (6.2%) and tuna-like (10.9%) species captures was recorded in subsurface sets. The probability of cetacean bycatch, however, was 78.5% lower in subsurface than in surface sets.
4. Cetacean bycatch in tuna drift gillnet fisheries has the potential to be significantly reduced at a relatively low cost for fishers. However, further research with an appropriate sampling design and a large sample size is required to confirm the efficacy of the proposed mitigation method. The acceptability and adoption of subsurface setting by fishers also needs to be further investigated. Despite some limitations, this preliminary study also highlights the importance of crew-based observer data as an alternative source of data when observers cannot be deployed on fishing vessels.

     

Multiple antibiotic resistant fecal coliforms in raw sewage

Fecal coliforms in raw sewage from three localities in Bahrain were tested for resistance to 9 commonly available antibiotics. Nineteen percent of the isolates resistant to at least two antibiotics, showed resistance to Nalidixic acid and 10% were resistant to all other 8 antibiotics tested. Transmissability of antibiotic resistance was temperature dependent and was demonstrated in 86.0% of resistant isolates. The antibiotic resistant organisms also survived longer than sensitive isolates in seawater under laboratory conditions. Over the counter availability of antibiotics and a high incidence of multiple antibiotic resistant coliforms have possible implications on public health.     

Characterization of resistance gene analogs from <Emphasis Type="Italic">Gossypium arboreum</Emphasis> and their evolutionary relationships with homologs from tetraploid cottons

Four cotton species (genus Gossypium) produce spinable fiber. The two diploid species of Asiatic origin, Gossypium arboreum and G. herbaceum, have been largely replaced by G. hirsutum. However, these diploid species are potentially a rich source of genes for the improvement of G. hrisutum, particularly in terms of providing resistance against biotic and abiotic stresses. As a first step towards understanding the mechanisms of resistance in cotton, we designed 24 non-degenerate primers based on resistance gene analogs (RGAs) cloned from G. hirsutum for screening a number of cotton species with the A and D genomes. Most of these RGAs are conserved on the A genome (G. arboreum), suggesting a bias towards this genome. The amplified RGAs from G. arboreum were cloned and their nucleotide and amino acid sequences compared with RGA sequences available in public databases. The majority of the RGAs identified were homologous to those isolated from G. hirsutum and G. barbadense, but their diversity was greater than expected at both the nucleotide and amino acid levels. These RGAs provide useful tools for the identification of full-length resistance genes from bacterial artificial chromosome and cDNA libraries.