ABSTRACTENVIRONMENTAL RISK ASSESSMENT FOR INTRODUCTION OF GENETICALLY ENGINEERED WEEVIL RESISTANT SWEETPOTATO IN UGANDABy Barbara Mugwanya ZaweddeGenetic engineering (GE) tools have been used for crop improvement for over two decades, however, widespread acceptance and cultivation of GE crops has been constrained in part by associated environmental concerns. Bt sweetpotato is one of the GE products being developed to address weevil infestation, which causes high yield losses in some parts of Africa where sweetpotato is considered a food security crop. To address the frequently raised concern of possible impact of GE crops on land race and varietal diversity, microsatellite marker analysis was performed to assess the level of genetic diversity in sweetpotato in Uganda and other parts of East Africa and compare to diversity present in samples from the proposed center of origin in South America A total of 260 sweetpotato accessions, collected from Uganda, Kenya, Tanzania, Ghana, Brazil and Peru, were characterized using 13 to 16 microsatellite markers. The Ugandan collection has a large number of distinct landrace genotypes, but there was low (6%) genetic variability between the Ugandan germplasm and accessions obtained from other East African countries. Within Uganda higher genetic variability (76%) was recorded within regions than among regions. To gain a better understanding of how diversity is maintained in farmers' fields, ethno-botanical surveys were performed within three sweetpotato producing regions of Uganda to analyze the considerations used by farmers when making decisions to maintain, incorporate and or discard varieties, and to assess the changes in the crop management practices implemented when adopting new cultivars that are, or are not, introduced in concert with promotional campaigns. In most districts, farmers were growing both landraces and released cultivars. Maintenance of traditional varieties was influenced by ecological conditions, socio-economic factors, and crop management practices such as drought, market and extension service access. To contribute to an environmental risk assessment for Bt sweetpotato, which is required in Ugandan prior to open release of any new GE crops, problem formulation was used to identify valued ecological entities in the receiving environment and possible harms associated with introducing a new technology. A participatory approach was taken using consultations with local Ugandan scientists and regulators with diverse expertise to identify agronomic practices and possible harms that may be associated with three GE crop-trait scenarios. Based on these consultations, the potential harms viewed to be most relevant for each scenario were identified. For GE weevil resistant sweetpotato, development of resistance by the pest, sweetpotato varietal diversity loss, diversity loss for other crops, and secondary pests were identified as the concerns that warrant greatest regulatory consideration. Information obtained from the sweetpotato biodiversity and farmer practices studies combined with existing literature was used to address the prioritized concerns. These analyses indicated that diversity loss for other crops and emergence of secondary pests were unlikely; development of resistance by the pests and loss of sweetpotato varietal diversity appear to be more likely, although not unique to deployment of GE crops. Possible risk management strategies to mitigate these concerns were suggested for consideration prior to open cultivation of weevil resistant sweetpotato varieties.
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