An Ulva armoricana extract protects plants against three powdery mildew pathogens

The protective activity of a crude extract prepared from the green macroalga, Ulva armoricana, previously shown to induce plant defence responses, was evaluated on three plant species, common bean, grapevine and cucumber, cultivated in the greenhouse and inoculated with three powdery mildew pathogens Erysiphe polygoni, E. necator and Sphareotheca fuliginea respectively. Chemical analyses showed that the extract was enriched in ulvans, which are green algae polysaccharides essentially composed of uronic acid and sulphated rhamnose. Weekly applications were performed by spraying of the green algal extract at various dilutions on bean, grapevine and cucumber leaves. A significant effect (50% protection) was observed using a dilution corresponding to about 3 g l⁻¹ dry matter and up to 90% reduction of symptom severity was obtained for the highest concentration (1/9 dilution, 6 g l⁻¹ dry matter) for the three plant species. To study the natural variability of the protective activity, five extracts prepared from algae batches harvested at different year periods were evaluated. Although polysaccharide composition varied among batches, all extracts elicit a reporter gene regulated by a defence-gene promoter in a transgenic tobacco line, and protect cucumber plants against powdery mildew infection. Together, these data demonstrate that U. armoricana is a reproducible source of active compounds which can be used to efficiently protect crop plants against powdery mildew diseases.     

Promoting native trees in shade coffee plantations of southern India: comparison of growth rates with the exotic <Emphasis Type="Italic">Grevillea robusta</Emphasis>

Traditional shade coffee plantations of Kodagu district, in the Western Ghats of southern India, harbor a high density and diversity of trees. Local farmers appreciate native biodiversity, but plantation economics and public policies drive them to gradually replace the original diversified cover with exotic shade trees such as Grevillea robusta, which grows fast and can be easily traded as timber. In order to identify and recommend native timber trees with fast growth rates, we compared the growth performance of four common native species against that of G. robusta, by fitting steel dendrometer bands on 332 shade trees. Results showed that in general G. robusta had the fastest growth rates, but large trees of the native Acrocarpus fraxinifolius had faster growth in the wet western side of the district. Computer projections of long term performance showed that most species were influenced by bioclimatic zone. Species-specific local environmental effects also occurred, including competition from coffee bushes for A. fraxinifolius, influence of aspect for G. robusta, and management block effects for Lagerstroemia microcarpa. Our results show that native species potentially could produce timber at rates equivalent to those of exotic species. However, as in many tropical countries, data on growth rates of native trees within mixed-cover plantations are scarce and this study underlines the urgent need to screen for fast-growing species. Such information provides a strong basis for recommending appropriate changes in public policies that would improve tree tenure security and encourage farmers to grow more native species.     

From inventory to consumer biomass availability—the ITOC model

Key message The application of the ITOC model allows the estimation of available biomass potentials from forests on the basis of National Forest Inventory data. The adaptation of the model to country-specific situations gives the possibility to further enhance the model calculations.

Context

With the rising demand for energy from renewable sources, up-to-date information about the available amount of biomass on a sustainable basis coming from forests became of interest to a wide group of stakeholders. The complexity of answering the question about amounts of biomass potentials from forests thereby increases from the regional to the European level.

Aims

The described ITOC model aims at providing a tool to develop a comparable data basis for the actual biomass potentials for consumption.

Methods

The ITOC model uses a harmonized net annual increment from the National Forest Inventories as a default value for the potential harvestable volume of timber. The model then calculates the total theoretical potential of biomass resources from forests. By accounting for harvesting restrictions and losses, the theoretical potential of biomass resources from forests is reduced and the actual biomass potentials for consumption estimated.

Results

The results from ITOC model calculations account for the difference between the amounts of wood measured in the forests and the actual biomass potentials which might be available for consumption under the model assumptions.

Conclusion

The gap between forest resource assessments and biomass potentials which are available for consumption can be addressed by using the ITOC model calculation results.

     

Competing Visions: Domestic Forests, Politics and Forest Policy in the Central Western Ghats of South India

Rural people in developing countries including India continue to access a number of types of ‘forests’ to meet specific needs such as fuelwood, fodder, food, non-timber forest produce and timber for both subsistence and income generation. While a plethora of terms exist to describe the types of forests that rural people use—such as farm forests, social forests, community forests and small-scale forests—the expression domestic forest has recently been proposed. Domestic forest is a term aimed at capturing the diversity of forests transformed and managed by rural communities and a way to introduce a new scientific domain that recognises that production and conservation can be reconciled and that local communities can be effective managers. This paper argues in the context of the central Western Ghats of south India that while the domestic forest concept is a useful umbrella term to capture the diversity of forests used by rural people, these domestic forests are often not autonomous local forests but sites of contestation between local actors and the state forest bureaucracy. Hence, a paradigm shift within the forest bureaucracy will only occur if the scientific forestry community questions its own normative views on forest management and sees forest policy as a means to recognise local claims and support existing practices of forest dependent communities.     

Forest liming durably impact the communities of ectomycorrhizas and fungal epigeous fruiting bodies

? Liming is a forestry practice used to counteract forest decline in acidic soils. It consists of direct Ca and Mg input to forest soil, which restores tree mineral nutrition, but also modifies microbial communities in soil. The aim of this study was to assess the effects of liming on both belowground (ectomycorrhizal root tips) and aboveground (epigeous sporocarps) fungal communities.

? Results showed that the modification of soil chemical properties (pH, and Ca-Mg contents versus total free Al and Fe concentrations) was a stronger factor of ECM community structuring than tree host. The species appearing in limed plots were ubiquist or known as good competitors and replaced acidophilic and stress species.

? At the sporocarp level, tree host was a stronger factor of community structuring than soil chemical properties associated with liming. On the whole, there was a shift in the community composition from a typical acidophilic forest fungal community of medium altitude in the untreated plots to a less typical one, with the reduced dominance of acidophilic fungi while many late-stage forest species appeared.

? We finally suggest a marker species (Russula ochroleuca) to assess both above and belowground effects of liming on ectomycorrhizal communities.

     

Reframing Community Forestry to Manage the Forest–Farm Interface

At the 2010 Montpellier conference on ‘Taking Stock of Smallholder and Community Forestry: Where do we go from here?’, researchers, policy-makers and practitioners came together to discuss historical trends and future directions for understanding and supporting forest sustainability and local livelihoods in forest-based communities. A consensus arising from these discussions was that there is a need to reframe and broaden approaches to understand forestry practised by smallholders and communities. The paper highlights three key topics from that discussion: (1) the need to reconsider definitions of community forestry, (2) the need to broaden understanding of rights surrounding forest resources and (3) the need to reframe research to focus on management of the forest–farm interface.     

Production of embryogenic tissues and regeneration of transgenic plants in cassava (Manihot esculenta Crantz)

Disorganised embryogenic tissues have been utilised as target tissues for transgene insertion and transgenic plant regeneration in cassava (Manihot esculenta). The production of friable embryogenic callus in fourteen geographically diverse cassava cultivars, from which eleven were established as embryogenic suspension cultures, is reported. Embryogenic tissues were similar in nature in all cultivars tested although there was variation in the time required to generate friable callus and the growth rates of suspension cultures. Regeneration of plants has been achieved from eight cultivars but varied significantly in efficiency, with cv. TMS 60444and Line 2 from Zimbabwe being the most responsive. Tissues from the remaining eight cultivars became arrested at globular and torpedo stages of regeneration indicating that they most likely process an inherent ability to produce plants but require further research to allow this to be realised. Significant numbers of transgenic plants containing transgenes for putative resistance to important viral diseases of cassava in addition to visual marker genes have been regenerated. Transgenic plants from three the cultivars TMS 60444, Bonoua Rouge and M.Col 1505 were recovered after particle bombardment of embryogenic suspension cultures. Correlation's have been made between abnormal leaf morphology and plant vigour with the use of embryogenic suspension cultures for transgene insertion. As an result friable embryogenic callus is now being successfully utilsed as the target tissue for genetic transformation and plant regeneration at ILTAB. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial analysis of soil surface hydraulic properties: Is infiltration method dependent?

The management of irrigated agricultural fields requires reliable information about soil hydraulic properties and their spatio-temporal variability. The spatial variability of saturated hydraulic conductivity, K_s and the alpha-parameter α_vG-2007 of the van Genuchten equation was reviewed on an agricultural loamy soil after a 17-year period of repeated conventional agricultural practices for tillage and planting. The Beerkan infiltration method and its algorithm BEST were used to characterize the soil through the van Genuchten and Brooks and Corey equations. Forty field measurements were made at each node of a 6 m × 7.5 m grid. The soil hydraulic properties and their spatial structure were compared to those recorded in 1990 on the same field soil, through the exponential form of the soil hydraulic conductivity given by the Gardner equation, using the Guelph Pressure Infiltrometer technique. No significant differences in the results obtained in 1990 and 2007 were observed for either particle-size distribution or dry bulk density. The mean value of α_vG-2007 was found to be identical to that of α_G-1990, while that of K_s-2007 was significantly smaller than that of K_s-1990. In contrast to the Gardner equation, the van Genuchten/Brooks and Corey expression was found to be more representative of a well-graded particle-size distribution of a loamy soil. The geostatistical analysis showed the two parameters, K_s and α_vG-2007, were autocorrelated up to about 30 and 21 m, respectively, as well as spatially positively correlated within a range of 30 m. Despite the difference in the mean values of K_s between the two studies, the spatial structures were similar to those found in the 1990 experiment except for the covariance sign. The similarity in autocorrelation ranges indicate that the spatial analysis of soil hydraulic properties is independent of the infiltration methods (i.e., measurement of an infiltration flux) used in the two studies, while the difference in the covariance sign may be linked to the use of two different techniques of soil hydraulic parameterization. The covariance values found in the 2007 campaign indicates a positive relationship between the two parameters, K_s and α_vG-2007. The spatial correlations of soil hydraulic parameters appear to be temporally stabilized, at least within the agro-pedo-climatic context of the study. This may be attributed to the soil textural properties which remain constant in time and to the structural properties which are constantly renewed by the cyclic agricultural practices. However, further experiments are needed to strengthen this result.     

Genotype x Bradyrhizobium japonicum strain interactions in dinitrogen fixation and agronomic traits of soybean (Glycine max L. Merr.)

Summary Bradyrhizobium japonicum strain G49 has been the only inoculum used in French soils. Soybean (Glycine max L. Merr.) cultivars were selected and tested according to their performances with this rhizobial strain. The aim of the present study was to determine the consequences of strain substitution on N₂ fixation abilities of various genotypes. Three genotypes and cultivar Weber, in combination with B. japonicum strain G49 or SMGS1, were cultivated in pots and tested for nitrogenase activity under differing nitrogen nutrition conditions. The reliability of ARA (acetylene reduction activity) measurement for assessing symbiotic nitrogen fixation under the experimental conditions used was checked. Genotypic variability for symbiotic fixation activity was observed with each strain under soil culture conditions; important genotype x strain interactions were also involved. These results were corroborated for the protein yield and other yield component performances of the various genotype-strain associations. Thus, in France, the replacement of strain G49 with another one might result in the alteration of the relative agronomic performances of the soybean cultivars, since N₂ fixation is considered as a major factor of soybean productivity.