Wolbachia Infection in Populations of Ostrinia furnacalis: Diversity,Prevalence, Phylogeny and Evidence for Horizontal Transmission

Wolbachia are maternally inherited endosymbiotic bacteria infecting a wide range of arthropods and filarial nematodes. They can induce various reproduction alterations in their hosts, including thelytokous parthenogenesis, cytoplasmic incompatibility (CI), feminization of genetic males and male killing. Here we investigated diversity and prevalence patterns of Wolbachia infection in 43 geographical populations of the Asian corn borer, Ostrinia furnacalis, in China and one population in North Korea. Based on Wolbachia surface protein gene (wsp) sequences, nine strains of Wolbachia (wFur1-wFur9), belonging to supergroups A and B, were identified in populations of O. furnacalis with an average infection rate of 10.5%. Superinfection commonly appeared in individuals of O. furnacalis and coinfection patterns were very complex. There was no specific pattern for the prevalence and distribution of the nine Wolbachia strains suggesting an intricate evolutionary history of Wolbachia infection in this species. The genetic similarity of the wFur1-wFur9 strains with those detected in two parasitoids of O. furnacalis, Macrocentrus cingulum and Lydella grisescens, strongly suggests host-parasitoid horizontal transmission.     

In vitro regeneration of Irvingia gabonensis by somatic embryogenesis

A productive genotype of Irvingia gabonensis were cultured in vitro for induction embryogenic calli, somatic embryogenesis and regeneration of plantlets. Fragments of young leaves were used as primary explants. Callogenesis was initiated by culture of explants during 30 days on Murashige and Skoog medium half strength (MS/2) supplemented with 1-6 mg L(-1) of 2,4-dichlorophenoxyacetic acid (2,4-D). The highest percentage of explants forming calli is 85.1% at 3 mg L(-1) of 2,4-D. Somatic embryos were obtained after a subculture of embryogenic calli during 60 days on MS/2 supplemented with 1-3 mg L(-1) of BAP. The highest percentage of embryogenic calli which differentiates somatic embryos is 63.8 +/- 2.3% at 1 mg L(-1) of 6-benzylaminopurine (BAP). The highest number of somatic embryos per callus which is 43.6 is obtained with 2 mg L(-1) of this phytohormone. When isolated from calli and sub-cultured during 30 days on MS/2 supplemented with 2 mg L(-1) of BAP, somatic embryos germinate with a highest percentage of 83%. The subculture of germinated somatic embryos on the same Basal Medium (BM) supplemented with 4 mg L(-1) of BAP and 2 mg L(-1) of Naphthalene Acetic Acid (NAA) during 80 days gives rise to the plantlets with 82.7 +/- 4.8% of success. With this combination, each plantlet has average length of 5.6 cm, bears 3.3 leaves and 7.2 roots with 1 or 2 pivoting roots. Plantlets acclimatized on a mixture sterilized soil/vermiculite at equal volume survive at 93%. Results of this study constitute a new way for a production of Irvingia gabonensis seedlings with pivoting root and they permit to arrest the difficulties of natural and horticultural reproduction.     

Evapotranspiration,irrigation water requirement,and water productivity of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) in the Sahelian environment

Rice is the main crop produced in the Senegal River Valley under the semiarid Sahelian climate where water resource management is critical for the resource use sustainability. However, very limited data exit on rice water use and irrigation water requirement in this water scarcity environment under climate change conditions. Understanding crop water requirements is essential for better irrigation practices, scheduling and efficient use of water. The objectives of this study were to estimate crop water use and irrigation water requirement of rice in the Senegal River Valley at Fanaye. Field experiments were conducted during the 2013 hot and dry season and wet season, and 2014 hot and dry season and wet seasons. Three nitrogen fertilizer treatments were applied to rice variety Sahel 108: 60, 120, and 180 kg N ha^?1. Rice water use was estimated by the two-step approach. Results indicated that crop actual evapotranspiration (ETa) varied from 632 to 929 mm with the highest ETa obtained during the hot and dry seasons. Irrigation water requirement varied from 863 to 1198 mm per season. Rice grain yield was function of the growing season and varied from 4.1 to 10.7 tons ha^?1 and increased with nitrogen fertilizer rate. Rice water use efficiency relative to ETa and irrigation requirements increased with nitrogen fertilizer rate while rice nitrogen use efficiency decreased with the nitrogen fertilizer rates. The results of this study can be used as a guideline for rice water use and irrigation water requirement for the irrigation design projects, consultants, universities, producers, and other operators within rice value chain in the Senegal River Valley.     

Economic impacts of climate change: profitability of freshwater aquaculture in China

Aquaculture is threatened by the climate change which includes changes in temperature, precipitation, drought, storms and floods. The socio‐economic impacts of climate change on aquaculture are difficult to assess due to the uncertainties regarding the extent and rate of predicted changes. By including bond indexes as climate change variables, this study constructed a provincial‐level panel data set to estimate the profits and productivity of the Chinese aquaculture. Results indicate that aquaculture production has heterogeneous responses to climate change. However, the majority of climate variables, including extreme weather events and long‐term climate changes, strongly affect aquaculture profits. Future research needs to focus on designing suitable adaptation measures in an interdisciplinary setting to address the challenges from natural risks and economic volatility.     

Modern and paleolimnological evidence for accelerated leaching and metal accumulation in soils in New England,caused by atmospheric deposition

Empirical field evidence for changing chemical processes in soils caused by atmospheric deposition of pollutants consists of: (1) Long-term water quality data including total dissolved solids, concentrations of specific metals (e.g. Ca), and conductivity; (2) Cation exchange capacity and base saturation values for soils located on precipitation pH gradients; (3) Lysimeter studies; and (4) Chemical analysis of organic soils on precipitation pH and metal gradients. For well-drained organic soils, as precipitation pH decreases, metals are differentially leached at an accelerated rate (Mn>Ca>Mg≥Zn>Cd and Na>Al). Experimental field and laboratory lysimeter studies on soil columns yield similar results, with increases in leaching rates for soil solutions with pH=3 up to 100 × values for soil solutions with pH=5. Nearly 100% of the Pb from precipitation is accumulating in the organic soil layer or sediments. Zn is accumulating in soils and sediments where the pH's of precipitation, soil solutions, and surface waters are generally above 5 to 5.5. At lower pH values Zn and other chemically similar elements are desorbed/leached (net) at an accelerated rate. Chemical analyses of dated sediment cores from high and low altitude lakes, with drainage basins relatively undisturbed for the last 200+ yr, reveal that increased deposition of metals on a regional scale started in the northeastern United States as early as 1880, consistent with increased fossil fuel consumption. This suggests acidified precipitation as early as 1880. Cores from historically acidified lakes (pH<≈5.3 to 5.5) indicate that, as acidification of surface waters occurs (caused by acidic deposition), concentrations of Zn, Mn, and Ca decrease in the sediment. Apparently the metals are leached from the detritus prior to sedimentation. This conclusion results from data from experimental acidification of sediment cores and the general observation that precipitation pH is generally ≥0.5 pH units lower than lake water pH. Accelerated leaching of soil in New England dates to earlier than 1900.     

Variability of stem and branch maintenance respiration in a Pinus pinaster tree

The relationship between maintenance respiration (Rm) of woody organs and their structural characteristics was explored in adult Pinus pinaster Ait. trees. We measured Rm on 75 stem and branch segments of different ages (from 3 to 24 years) and diameters (from 1 to 35 cm). The temperature response of Rm was derived from field measurements based on a classical exponential function with Q10 = 2.13. Relationships between Rm and the dimensions of the woody organs were analyzed under controlled conditions in the laboratory. The surface area of a woody organ was a better predictor of Rm than volume, but surface area failed to account for the observed within-tree variability of Rm among stems, branches and twigs. Two simple models were proposed to predict the variability of Rm at 15 degrees C in an adult tree. Model 1, a linear function model based on the dry mass and nitrogen concentration of sapwood and phloem tissues, explained most of the variability of Rm in branches and stems (R2 = 0.97). We concluded that the respective contributions of the phloem and sapwood depend on the location and diameter of the woody organ. Model 2, a power-law function model based on the length, diameter and age of the sample, explained the same variance of Rm as Model 1 and is appropriate for scaling Rm to the stand level. Models 1 and 2 appear to explain a larger variability of Rm than models based on stem area or sapwood mass.     

Infection of citrus pollen grains by Colletotrichum acutatum

Postbloom fruit drop (PFD), an important disease caused by Colletotrichum spp., affects citrus yields in Brazil. PFD is characterised by the presence of necrotic lesions on the petals and stigmas of citrus flowers and by the subsequent abscission of young fruit. PFD epidemics have high disease progress rates, which is unusual for a pathogen that produces acervuli and is dispersed by rain. It is possible that other dispersal agents, such as insects and pollen, are involved in the spread of this disease. The objective of this work was to test whether citrus pollen grains can be colonised by Colletotrichum acutatum. Studies using light and electron microscopy showed that the pollen of Citrus sinensis can be infected by C. acutatum. This pathogen can penetrate and colonise citrus pollen grains 24 h after inoculation with the pathogen. The germ tube of conidia either penetrates the pollen sporodermis directly or passes through pollen germ pores. A single hypha can colonise more than one pollen grain. On the surface of the stigma, conidium formation can be observed. This study shows that Citrus sinensis pollen may, in fact, play a role in the spread of C. acutatum in citrus orchards.     

Thinking outside the patch: a multi-species comparison of conceptual models from real-world landscapes

Context

When modeling a species’ distribution, landscapes can alternatively be conceptualized following patch- or gradient-based approaches. However, choosing the most suitable conceptualization is difficult and methods for empirical validation are still lacking.

Objectives

To address the conditions under which a given conceptual model is more suitable, taking into account landscape context and species trait dependency effects. Patch- and gradient-based conceptualizations were built based on two structurally different landscapes: variegated and mosaic. We hypothesize that: (H1) gradient-based models better describe variegated landscapes while patch-based models perform better in mosaic landscapes; and (H2) gradient-based models will fit generalist species better while patch-based models will suit specialists better.

Methods

We modeled the distribution of eleven bird species in each landscape using each conceptualization. We determined the suitability of each conceptual model to fit statistical models by looking for cross-species responses and deviations from best models.

Results

We found no clear support for our hypotheses. Although patch-based models performed better in mosaic landscapes (H1), they also provided useful conceptualizations in variegated landscapes. However, when patches showed high heterogeneity, gradient-based approaches better fit specialist species (H2).

Conclusions

The suitability of a given conceptual model depends on the interaction between species habitat specialization, and the intrinsic spatial heterogeneity of the landscape and the ability of each conceptualization to capture it. Gradient-based models provide better information on resource allocation, while patch-based models offer a simplified perspective on landscape attributes. Future research should consider the nature of both species and landscapes in order to avoid bias from inadequate landscape conceptualizations.