On trial: agricultural biotechnology in Africa

Increasing agricultural productivity and adapting farming to climate change are central to Africa’s development prospects. There are important opportunities to enhance yields and increase resilience through the adoption of improved crop varieties. In some cases, biotechnology, and in particular genetic modification (GM), offers advantages over conventional plant-breeding approaches. Accordingly there are a various projects under way to develop new GM varieties for African farmers, ranging from drought-resistant maize to varieties of cassava, banana, sorghum, cowpea and sweet potato with resistance to pests and disease. In addition to government funds, these projects have also attracted the support of influential donor agencies and philanthropic foundations. However, despite the expenditure of considerable resources, the potential of GM in Africa is not being realized. So far no GM trait developed for African farmers has been put to use. Multiple barriers inhibit the development and adoption of pro-poor GM varieties in Africa. On the demand side, farmers may be reluctant to adopt GM varieties owing to a lack of export opportunities and distrust of the technology among local consumers. Farmers may also be concerned about exploitation by transnational seed companies (despite the fact that development of new GM technologies in Africa is dominated by the public sector). On the supply side, donor funding struggles to match the long timescales of research and development, while incentives among research scientists may be poorly aligned with farmer outcomes. Non-existent, poorly functioning or overly punitive regulatory regimes discourage investment. The most important barriers – such as regulatory constraints, consumer distrust and weak farmer demand – must be understood in the context of wider social and political dynamics surrounding GM, typified by misinformation, polarized public discourse, and dysfunctional and opportunistic politics. The result is most GM projects becoming ‘stuck’ at the field trial stage without ever progressing to release. This ‘convenient deadlock’ of continual field trials allows governments to manage political risks by effectively balancing the demands of pro-GM and anti-GM lobbies – proponents of GM have a pipeline of technologies, while opponents are appeased by the failure of any to gain approval. The disabling socio-political environment for GM development in Africa greatly reduces the efficacy of investment in this technology. This has two important implications. First, technology development needs to be located within a wider project of transformation that engages key actors – most notably politicians, policy-makers and farmers – as stakeholders from the outset, and includes strategies to address multiple demand- and supply-side barriers. Second, successful adoption is more likely in countries with less disabling political conditions, characterized by lower levels of consumer distrust and opposition, genuine farmer demand and demonstrable commitment from government. Focusing efforts and resources on a small number of ‘best bet’ countries will also allow donors and technology providers to support more ambitious, transformational projects led by national governments

Renormalized One-loop Theory of Correlations in Disordered Diblock Copolymers

A renormalized one-loop theory (ROL) is used to calculate corrections to the random phase approximation (RPA) for the structure factor \Sc(q) in disordered diblock copolymer melts. Predictions are given for the peak intensity $S(q^{\star})$, peak position $q^{\star}$, and single-chain statistics for symmetric and asymmetric copolymers as functions of $\chi N$, where $\chi$ is the Flory-Huggins interaction parameter and $N$ is the degree of polymerization. The ROL and Fredrickson-Helfand (FH) theories are found to yield asymptotically equivalent results for the dependence of the peak intensity $S(q^{\star})$ upon $\chi N$ for symmetric diblock copolymers in the limit of strong scattering, or large $\chi N$, but yield qualitatively different predictions for symmetric copolymers far from the ODT and for asymmetric copolymers. The ROL theory predicts a suppression of $S(q^\star)$ and a decrease of $q^{\star}$ for large values of $\chi N$, relative to the RPA predictions, but an enhancement of $S(q^{\star})$ and an increase in $q^{\star}$ for small $\chi N$ ($\chi N < 5$). By separating intra- and inter-molecular contributions to $S^{-1}(q)$, we show that the decrease in $q^{\star}$ near the ODT is caused by the $q$ dependence of the intermolecular direct correlation function, and is unrelated to any change in single-chain statistics, but that the increase in $q^{\star}$ at small values of $\chi N$ is a result of non-Gaussian single-chain statistics.Comment: 16 pages, 13 figures, submitted to J. Chem. Phy

Inactivation of baculovirus by isoflavonoids on chickpea (Cicer arietinum) leaf surfaces reduces the efficacy of nucleopolyhedrovirus against Helicoverpa armigera

Biological pesticides based on nucleopolyhedroviruses (NPVs) can provide an effective and environmentally benign alternative to synthetic chemicals. On some crops, however, the efficacy and persistence of NPVs is known to be reduced by plant specific factors. The present study investigated the efficacy of Helicoverpa armigera NPV (HearNPV) for control of H. armigera larvae, and showed that chickpea reduced the infectivity of virus occlusion bodies (OBs) exposed to the leaf surface of chickpea for at least 1 h. The degree of inactivation was greater on chickpea than that previously reported on cotton, and the mode of action is different from that of cotton. The effect was observed for larvae that consumed OBs on chickpea leaves, but it also occurred when OBs were removed after exposure to plants and inoculated onto artificial diet, indicating that inhibition was leaf surfacerelated and permanent. Despite their profuse exudation from trichomes on chickpea leaves and their low pH, organic acids—primarily oxalic and malic acid—caused no inhibition. When HearNPV was incubated with biochanin A and sissotrin, however, two minor constituents of chickpea leaf extracts, OB activity was reduced significantly. These two isoflavonoids increased in concentration by up to 3 times within 1 h of spraying the virus suspension onto the plants and also when spraying only the carrier, indicating induction was in response to spraying and not a specific response to the HearNPV. Although inactivation by the isoflavonoids did not account completely for the level of effect recorded on whole plants, this work constitutes evidence for a novel mechanism of NPV inactivation in legumes. Expanding the use of biological pesticides on legume crops will be dependent upon the development of suitable formulations for OBs to overcome plant secondary chemical effects

Renormalization of the one-loop theory of fluctuations in polymer blends and diblock copolymer melts

Attempts to use coarse-grained molecular theories to calculate corrections to the random-phase approximation (RPA) for correlations in polymer mixtures have been plagued by an unwanted sensitivity to the value of an arbitrary cutoff length, {\it i.e.}, by an ultraviolet (UV) divergence. We analyze the UV divergence of the inverse structure factor $S^{-1}(k)$ predicted by a `one-loop' approximation similar to that used in several previous studies. We consider both miscible homopolymer blends and disordered diblock copolymer melts. We show, in both cases, that all UV divergent contributions can be absorbed into a renormalization of the values of the phenomenological parameters of a generalized self-consistent field theory (SCFT). This observation allows the construction of a UV convergent theory of corrections to SCFT phenomenology. The UV-divergent one-loop contribution to $S^{-1}(k)$ are shown to be the sum of: (i) a $k$-independent contribution that arises from a renormalization of the effective $\chi$ parameter, (ii) a $k$-dependent contribution that arises from a renormalization of monomer statistical segment lengths, (iii) a contribution proportional to $k^{2}$ that arises from a square-gradient contribution to the one-loop fluctuation free energy, and (iv) a $k$-dependent contribution that is inversely proportional to the degree of polymerization, which arises from local perturbations in fluid structure near chain ends and near junctions between blocks in block copolymers.Comment: 35 pages, 2 figure

Development of a real-time qPCR assay for quantification of covert baculovirus infections in a major African crop pest

Many pathogens and parasites are present in host individuals and populations without any obvious signs of disease. This is particularly true for baculoviruses infecting lepidopteran hosts, where studies have shown that covert persistent viral infections are almost ubiquitous in many species. To date, the infection intensity of covert viruses has rarely been quantified. In this study, we investigated the dynamics of a covert baculovirus infection within the lepidopteran crop pest Spodoptera exempta. A real-time quantitative polymerase chain reaction (qPCR) procedure using a 5' nuclease hydrolysis (TaqMan) probe was developed for specific detection and quantification of Spodoptera exempta nucleopolyhedrovirus (SpexNPV). The qPCR assay indicated that covert baculovirus dynamics varied considerably over the course of the host life-cycle, with infection load peaking in early larval instars and being lowest in adults and final-instar larvae. Adult dissections indicated that, contrary to expectation, viral load aggregation was highest in the head, wings and legs, and lowest in the thorax and abdomen. The data presented here have broad implications relating to our understanding of transmission patterns of baculoviruses and the role of covert infections in host-pathogen dynamics

Promoting the adoption of improved ICM technologies in chickpea by poor farmers in Nepal

Chickpea is an important source of protein in Nepal for both poor rural and urban families. Yields of legumes including chickpea have decreased in recent years, primarily due to disease and insect pest problems, and the reluctance of farmers to invest time and money in a crop which increasingly fails. This project aimed to improve, validate and evaluate a complete integrated crop management (ICM) strategy for chickpea on farms; to persuade farmers to adopt the strategy through workshops and farm trials in some of the poorest areas of Nepal; and to promote the strategy widely to the press. and other stakeholders. The improved seed and technologies offered were in high demand by farmers, and the project produced evidence to show that the outputs (increased yield of a cash crop) have been translated into significant impacts on livelihood, including improved housing, debt repayment, education costs, clothes and healthcare. The value of the improved seed has been impressive and will benefit farmers in the longer term. An innovative promotional strategy promoted the findings to policymakers as well as farmers, and used the popular media in Nepal and the UK to publicise the wor

Orbital dependent nucleonic pairing in the lightest known isotopes of tin

By studying the 109Xe-->105Te-->101Sn superallowed alpha-decay chain, we observe low-lying states in 101Sn, the one-neutron system outside doubly magic 100Sn. We find that the spins of the ground state (J = 7=2) and first excited state (J = 5=2) in 101Sn are reversed with respect to the traditional level ordering postulated for 103Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations, dominate.Comment: 5 pages 3 figure

Trans-generational viral transmission and immune priming are dose-dependent

It is becoming increasingly apparent that trans-generational immune priming (i.e. the transfer of the parental immunological experience to its progeny resulting in offspring protection from pathogens that persist across generations) is a common phenomenon not only in vertebrates, but also invertebrates. Likewise, it is known that covert pathogenic infections may become 'triggered' into an overt infection by various stimuli, including exposure to heterologous infections. Yet rarely have both phenomena been explored in parallel. Using as a model system the African armyworm (Spodoptera exempta), an eruptive agricultural pest, and its endemic dsDNA virus (Spodoptera exempta nucleopolyhedrovirus, SpexNPV), the aim of this study was to explore the impact of parental inoculating-dose on trans-generational pathogen transmission and immune priming (in its broadest sense). Larvae were orally-challenged with one of five doses of SpexNPV and survivors from these treatments were mated and their offspring monitored for viral mortality. Offspring from parents challenged with low viral doses showed evidence of 'immune priming' (i.e. enhanced survival following SpexNPV challenge); in contrast, offspring from parents challenged with higher viral doses exhibited greater susceptibility to viral challenge. Most offspring larvae died of the virus they were orally-challenged with; in contrast, most offspring from parents that had been challenged with the highest doses were killed by the vertically-transmitted virus (90%) and not the challenge virus. These results demonstrate that the outcome of a potentially lethal virus challenge is critically dependent on the level of exposure to virus in the parental generation - either increasing resistance at very low parental viral doses (consistent with trans-generational immune-priming) or increasing susceptibility at higher parental doses (consistent with virus triggering). We discuss the implications of these findings for understanding both natural epizootics of baculoviruses and for using them as biological control agents

Genetic modification for disease resistance: a position paper

This Position Paper was prepared by members of the Task Force on Global Food Security of the International Society for Plant Pathology. An objective approach is proposed to the assessment of the potential of genetic modification (GM) to reduce the impact of crop diseases. The addition of GM to the plant breeder’s conventional toolbox facilitates gene-by-gene introduction into breeding programmes of well defined characters, while also allowing access to genes from a greatly extended range of organisms. The current status of GM crops is outlined. GM could make an additional contribution to food security but its potential has been controversial, sometimes because of fixed views that GM is unnatural and risky. These have no factual basis: GM technology, where adopted, is widely regulated and no evidence has been reported of adverse consequences for human health. The potential benefits of GM could be particularly valuable for the developing world but there are numerous constraints. These include cost, inadequate seed supply systems, reluctance to adopt unfamiliar technology, concern about markets, inadequacy of local regulatory systems, mismatch between research and growers’ needs, and limited technical resources. The lower cost of new gene-editing methods should open the practice of GM beyond multinational corporations. As yet there are few examples of utilization of GM-based resistance to plant diseases. Two cases, papaya ringspot virus and banana xanthomonas wilt, are outlined. In the developing world there are many more potential cases whose progress is prevented by the absence of adequate biosafety regulation. It is concluded that there is untapped potential for using GM to introduce disease resistance. An objective approach to mobilizing this potential is recommended, to address the severe impact of plant disease on food security

Racial Differences in Exposure and Reactivity to Daily Family Stressors

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91326/1/j.1741-3737.2012.00971.x.pd