Salvinia plants in trade: what species are we actually talking about?

Incorrect labelling of plants in trade and misidentification are widespread. Likewise, in trade numerous names are being used for the ornamental aquatic plant known as ‘Kariba weed’, but rarely the correct scientific name Salvinia molesta Mitch. For inspection services of EPPO member countries, correct identification of S. molesta has become important since the species was added to the EPPO A2 List and the List of Union concern in accordance with EU regulation 1143/2014 based on an EPPO Pest Risk Analysis (PRA) for the species. Inspections and a targetted survey of Salvinia plants in trade in the Netherlands were performed and additional material was obtained from wild sources in South Africa, Hungary and the United States. Specimen identification was verified by comparison with the herbarium collection at Naturalis Biodiversity Center in Leiden and with the sequences available in NCBI GenBank database. This paper provides the tools to correctly identity the relevant Salvinia species.     

Quantum spin hall insulator state in HgTe quantum wells

Recent theory predicted that the quantum spin Hall effect, a fundamentally new quantum state of matter that exists at zero external magnetic field, may be realized in HgTe/(Hg,Cd)Te quantum wells. We fabricated such sample structures with low density and high mobility in which we could tune, through an external gate voltage, the carrier conduction from n-type to p-type, passing through an insulating regime. For thin quantum wells with well width d < 6.3 nanometers, the insulating regime showed the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d > 6.3 nanometers), the nominally insulating regime showed a plateau of residual conductance close to 2e(2)/h, where e is the electron charge and h is Planck's constant. The residual conductance was independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance was destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d = 6.3 nanometers, was also independently determined from the magnetic field-induced insulator-to-metal transition. These observations provide experimental evidence of the quantum spin Hall effect.     

Adaptive management in agricultural innovation systems: The interactions between innovation networks and their environment

The purpose of this article is to investigate effective reformism: strategies that innovation networks deploy to create changes in their environment in order to establish a more conducive context for the realization and durable embedding of their innovation projects. Using a case study approach, effective reformism efforts are analyzed in a technological innovation trajectory related to the implementation of a new poultry husbandry system and an organizational innovation trajectory concerning new ways of co-operation among individual farms to establish economies of scale. The findings reinforce the idea, emerging from a complexity perspective on agricultural innovation systems, that interaction between innovation networks and their environment is only steerable to a limited extent. Nonetheless, innovation networks can enhance effective reformism by creating tangible visions that serve as vehicles to create understanding about the innovation and mobilize support for it, and by employing several kinds of boundary spanning individuals that are able to forge effective connections between innovation networks and their environment. Because innovation networks can only partially influence their institutional environment, and because unintended consequences of actions and random events influence the course of the innovation process, innovation network actors need to continuously re-interpret the contexts in which they move. This constant reflection by the innovating actors on their position vis-à-vis their environment needs to be supported by dedicated facilitators and monitoring and evaluation methods aimed at system learning. This implies that agricultural innovation policies should, instead of aiming to fully plan and control innovation, foster the emergence of such flexible support instruments that enable adaptive innovation management.     

Breakdown of Pl2, a major gene of resistance to apple powdery mildew, in a French experimental orchard

Pl2 , a major resistance gene to powdery mildew originating from Malus zumi , is mainly used in apple-breeding programmes. In an experimental orchard in France, an increase of susceptibility to powdery mildew was observed on apple genotypes carrying Pl2 . This increase of susceptibility could not be explained by an effect of the age of the trees, or by an effect of the amount of inoculum on expression of the resistance Pl2 . It was demonstrated by tests of pathogenicity in controlled conditions that isolates of Podosphaera leucotricha sampled in this orchard were virulent to Pl2 . The appearance of virulent isolates within 6 years after planting apple genotypes selected for the presence of Pl2 resulted in a breakdown of the resistance. Ten years after planting, the percentage of genotypes that were still resistant to powdery mildew varied between 2 and 56%, depending on the progenies. This suggested that additional quantitative resistance genes may influence the durability of the resistance Pl2 .     

Live attenuated malaria vaccine designed to protect through hepatic CD8⁺ T cell immunity

Our goal is to develop a vaccine that sustainably prevents Plasmodium falciparum (Pf) malaria in ≥80% of recipients. Pf sporozoites (PfSPZ) administered by mosquito bites are the only immunogens shown to induce such protection in humans. Such protection is thought to be mediated by CD8(+) T cells in the liver that secrete interferon-γ (IFN-γ). We report that purified irradiated PfSPZ administered to 80 volunteers by needle inoculation in the skin was safe, but suboptimally immunogenic and protective. Animal studies demonstrated that intravenous immunization was critical for inducing a high frequency of PfSPZ-specific CD8(+), IFN-γ-producing T cells in the liver (nonhuman primates, mice) and conferring protection (mice). Our results suggest that intravenous administration of this vaccine will lead to the prevention of infection with Pf malaria.     

Chemical Composition of the Uranium Tail Storages at Kadji-Sai (Southern Shore of Issyk-Kul Lake, Kyrgyzstan)

In 1996, an abandoned uranium mine was re-discovered in the Djilubulak ephemeral stream valley on the southern shore of Issyk-Kul - one of the largest and most pristine lakes in the world. The tail storages from the past mining may pose a pollution hazard to the lake water and sediments. A chain of six protective pools interconnected by drain pipes descend from the abandoned mine and processing plant down the Djilubulak stream valley. To assess the effectiveness of these catch pools and the scale of pollution risk the investigation of tail storages composition was performed. As a result, three sources of anomalous radioactivity were discovered: 1. Natural brown coal with the mean total radioactivity value not exceeding 16 kBq kg^-1, with U being in state of equilibrium with Ra. 2. Ashes depleted in U (relative to Ra) with the mean radioactivity reaching 49 kBq kg^-1, mostly due to the Ra content. 3. Clay and silt from the artificial protective pools where U activity (up to 2—2.5 kBq kg^-1) significantly exceeds that of Ra indicating recent process of U enrichment. Uranium in these pools is accompanied by very high contents of heavy metals such as Cu, Zn, Cd, Ni, Cr, and to a smaller degree Pb, Mo, Hg, Ag. From the upper catch pool to the lower ones the content of U and some heavy metals diminishes. Within the two lowest pools neither U nor heavy metal contents exceed background values (U < 0.1 kBq kg^-1). It appears that the system of catch pools effectively protects Lake Issyk-Kul from inorganic pollutants at the present time. However, a flash flood or other catastrophic event could breach the catch pool dams and carry radioactive elements and heavy metals into the Djilubulak stream valley and the lake.     

Genetic analysis of resistance to clubroot (Plasmodiophora brassicae Woron) in two Brassica oleracea groups (ssp. acephala and ssp. botrytis) through diallel analysis

Clubroot, caused by Plasmodiophora brassicae Woron, is a major disease of cruciferous crops and few sources of resistance have been detected and genetically studied in the Brassica oleracea species. In this study, two diallel mating systems using resistant kale lines and susceptible cauliflower lines were performed. Resistance was assessed from a disease index evaluated on young plants artificially inoculated with local isolates of the parasite. Both general and specific combining ability effects (GCA and SCA) and partly reciprocal effects were demonstrated. Resistance inheritance was, however, characterized by a predominance of additive genetic effects (GCA). Three groups of parent lines could be separated; kale lines with very high resistance, kale lines with intermediate resistance and susceptible cauliflower lines. In the two kale groups, two genetically different resistance types were suggested and various recurrent selection procedures are proposed following the diallel results.     

Hands off but Strings Attached: The Contradictions of Policy-induced Demand-driven Agricultural Extension

Although many governments have privatized their agricultural extension services, there is widespread agreement that the public sector still needs to play a role in the “agricultural knowledge market” in order to prevent market failure and other undesirable phenomena. However, appropriate mechanisms for intervention in the agricultural knowledge market are still in their infancy. This article discusses the case of the Nutrient Management Support Service (NMSS), a government-funded support service in The Netherlands designed to optimize the fit between the demand and supply of “agricultural knowledge products” that reduce nutrient emissions into the environment. The activities of the support service were four-fold: (1) distributing vouchers to farmers, (2) establishing mechanisms for quality control, (3) facilitating the articulation of end-users’ needs, and (4) improving market transparency. We analyze the extent to which the NMSS has succeeded in supporting a demand-driven knowledge market for nutrient management issues. We question some of the conceptual and practical assumptions underlying this style of intervention. In addition, we argue that the notion of demand requires considerable refinement before it can be useful for guiding state involvement in demand-driven extension. Laurens Klerkx holds a MSc in Tropical Land Use from Wageningen University. He is currently working on his PhD. His research focuses on how needs are articulated in demand-driven agricultural innovation processes and how newly emerging institutions such as knowledge brokers, knowledge networks, and innovation facilitators support this demand-driven agricultural innovation. Karin de Grip studied Tropical Agriculture (BSc) and, after working for 3 years in Indonesia in development co-operation, joined the MSc program in Management of Agri-ecological Knowledge and Social Change at Wageningen University. Her specific foci and interests include interactive knowledge development processes, learning processes, knowledge exchange and innovation networks, enforcement of knowledge markets, and demand-driven extension. Cees Leeuwis is professor of Communication and Innovation Studies at Wageningen University. He holds a MSc in Rural Sociology and a PhD in Communication and Innovation Studies. His research focuses on (a) the role of new interactive and cross-disciplinary approaches in bringing about coherent innovations, (b) the analysis of social learning and conflict management in networks, and (c) the way in which the privatization of research and extension institutions affects public sphere innovation processes.