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The year 2015 marked the 20th year of the commercialisation of genetically modified (GM) crops. During the period from 1996 to 2014, the global hectarage of these crops increased 100-fold, making it the fastest adopted crop technology in recent times. The overall economic gains from these crops have been estimated to be USD133.4 billion over the period from 1996 to 2013, and have been divided roughly 50% each to farmers in developed and developing countries. The environmental benefits include contributing to the practice of minimal till agriculture and a decrease in the use of pesticides. But what are the downsides of this technology? In this review I look at some of the problems related to weeds becoming resistant to glyphosate (the main ingredient that is used on herbicide tolerant crops), how these can be overcome and whether glyphosate can cause cancer. I also discuss the problem of insects becoming resistant to the toxins that are used in insect resistant crops and how these are being addressed. I look at what scientists around the world are saying on this topic and then consider GM crops that are in the pipeline of benefit to developing countries and whether any of these are likely to be commercialised in the foreseeable future. [ABSTRACT FROM AUTHOR]

A number of new crops have been developed that address important traits of particular relevance for smallholder farmers in Africa. Scientists, policy makers, and other stakeholders have raised concerns that the approval process for these new crops causes delays that are often scientifically unjustified. This article develops a real option model for the optimal regulation of a risky technology that enhances economic welfare and reduces malnutrition. We consider gradual adoption of the technology and show that delaying approval reduces uncertainty about perceived risks of the technology. Optimal conditions for approval incorporate parameters of the stochastic processes governing the dynamics of risk. The model is applied to three cases of improved crops, which either are, or are expected to be, delayed by the regulatory process. The benefits and costs of the crops are presented in a partial equilibrium that considers changes in adoption over time and the foregone benefits caused by a delay in approval under irreversibility and uncertainty. We derive the equilibrium conditions where the net-benefits of the technology equal the costs that would justify a delay. The sooner information about the safety of the technology arrive, the lower the costs for justifying a delay need to be i.e. it pays more to delay. The costs of a delay can be substantial: e.g. a one year delay in approval of the pod-borer resistant cowpea in Nigeria will cost the country about 33 million USD to 46 million USD and between 100 and 3,000 lives. [ABSTRACT FROM AUTHOR]

Plant diseases not found in many other parts of the world can be found in Africa. These diseases severely hinder crop production, potentially resulting in a lack of food security. Many of the disease problems are amenable to both classical and modern breeding solutions. However, some are challenging diseases that require the use of genetic modification. This paper discusses some of the diseases whereby genetically modified crops (GMO) can provide a solution. They include maize resistant to the endemic African Maize streak virus, cassava resistant to Cassava mosaic virus, and bananas resistant to bacterial wilt. In addition, other traits of value to farmers in Africa may include maize resistant to insects, post-harvest fungi and to weeds, drought-tolerant maize and vitamin-enriched crops. Consideration is given to some of the concerns preventing governments from approving the commercialization of these crops, including food and safety issues. [ABSTRACT FROM AUTHOR]

Maize streak virus (MSV), which causes maize streak disease (MSD), is the major viral pathogenic constraint on maize production in Africa. Type member of the Mastrevirus genus in the family Geminiviridae, MSV has a 2.7 kb, single-stranded circular DNA genome encoding a coat protein, movement protein, and the two replication-associated proteins Rep and RepA. While we have previously developed MSV-resistant transgenic maize lines constitutively expressing “dominant negative mutant” versions of the MSV Rep, the only transgenes we could use were those that caused no developmental defects during the regeneration of plants in tissue culture. A better transgene expression system would be an inducible one, where resistance-conferring transgenes are expressed only in MSV-infected cells. However, most known inducible transgene expression systems are hampered by background or “leaky” expression in the absence of the inducer. Here we describe an adaptation of the recently developed INPACT system to express MSV-derived resistance genes in cell culture. Split gene cassette constructs (SGCs) were developed containing three different transgenes in combination with three different promoter sequences. In each SGC, the transgene was split such that it would be translatable only in the presence of an infecting MSV’s replication associated protein. We used a quantitative real-time PCR assay to show that one of these SGCs (pSPLITrepIII-Rb-Ubi) inducibly inhibits MSV replication as efficiently as does a constitutively expressed transgene that has previously proven effective in protecting transgenic maize from MSV. In addition, in our cell-culture based assay pSPLITrepIII-Rb-Ubi inhibited replication of diverse MSV strains, and even, albeit to a lesser extent, of a different mastrevirus species. The application of this new technology to MSV resistance in maize could allow a better, more acceptable product. [ABSTRACT FROM AUTHOR]

Abstract: Geminiviruses infect a wide range of economically important crop plants. This review covers genetic engineering approaches currently being evaluated for the development of crops resistant to geminiviruses. In the past, most of these have involved pathogen-derived resistance strategies such as the expression of mutant or truncated viral proteins that interfere with virus infection, or transcription of viral RNA sequences that silence the expression of virus genes. Recently, however, alternatives to pathogen-derived resistance have been investigated. These include the use of geminivirus-inducible toxic proteins to kill infected cells, and the expression of DNA binding proteins, peptide aptamers or GroEL homologues that either disrupt geminivirus infections or lessen their harmful effects. Despite moderate successes in the engineering of geminivirus resistance using many of these strategies, no comparative data are available either on the relative merits of different approaches, or on how well the various resistant transgenic plants that have been produced will fare in the field. We anticipate that high geminivirus mutation and recombination rates could seriously undermine the durability of most currently available resistance transgenes. It should, however, be possible to achieve robust transgenic geminivirus resistance either by using mixtures of genes targeting multiple virus processes via multiple mechanisms, or by using “tolerance” genes that alleviate symptoms but do not selectively favour resistance-breaking virus mutants. [Copyright &y& Elsevier]