The VIRCA Project

Taylor, Nigel J.; Halsey, Mark; Gaitán-Solís, Eliana; Anderson, Paul E.; Gichuki, S.; Miano, Douglas Watuku; Bua, A.; Alicai, Titus; Fauquet, Claude

doi:10.4161/gmcr.19144

Cited by 36 publications

(16 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is, however, highly susceptible to CBSD. These qualities make TME 204 an ideal target for improvement within the VIRCA project, which aims to bring CMD- and CBSD-resistant planting material to smallholder farmers in East Africa (Taylor et al, 2012). We previously reported field resistance to CBSD generated from an inverted repeat construct carrying the CP of UCBSV (p718) (Ogwok et al, 2012; Odipio et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Field Level RNAi-Mediated Resistance to Cassava Brown Streak Disease across Multiple Cropping Cycles and Diverse East African Agro-Ecological Locations

et al. 2017

Self Cite

View full text Add to dashboard Cite

Cassava brown streak disease (CBSD) presents a serious threat to cassava production in East and Central Africa. Currently, no cultivars with high levels of resistance to CBSD are available to farmers. Transgenic RNAi technology was employed to combat CBSD by fusing coat protein (CP) sequences from Ugandan cassava brown streak virus (UCBSV) and Cassava brown streak virus (CBSV) to create an inverted repeat construct (p5001) driven by the constitutive Cassava vein mosaic virus promoter. Twenty-five plant lines of cultivar TME 204 expressing varying levels of small interfering RNAs (siRNAs) were established in confined field trials (CFTs) in Uganda and Kenya. Within an initial CFT at Namulonge, Uganda, non-transgenic TME 204 plants developed foliar and storage root CBSD incidences at 96–100% by 12 months after planting. In contrast, 16 of the 25 p5001 transgenic lines showed no foliar symptoms and had less than 8% of their storage roots symptomatic for CBSD. A direct positive correlation was seen between levels of resistance to CBSD and expression of transgenic CP-derived siRNAs. A subsequent CFT was established at Namulonge using stem cuttings from the initial trial. All transgenic lines established remained asymptomatic for CBSD, while 98% of the non-transgenic TME 204 stake-derived plants developed storage roots symptomatic for CBSD. Similarly, very high levels of resistance to CBSD were demonstrated by TME 204 p5001 RNAi lines grown within a CFT over a full cropping cycle at Mtwapa, coastal Kenya. Sequence analysis of CBSD causal viruses present at the trial sites showed that the transgenic lines were exposed to both CBSV and UCBSV, and that the sequenced isolates shared >90% CP identity with transgenic CP sequences expressed by the p5001 inverted repeat expression cassette. These results demonstrate very high levels of field resistance to CBSD conferred by the p5001 RNAi construct at diverse agro-ecological locations, and across the vegetative cropping cycle.

show abstract

Section: Discussionmentioning

confidence: 99%

“…The Virus Resistant Cassava for Africa (VIRCA) project aims to utilize RNAi to generate and deliver cassava with enhanced resistance to CBSD to farmers in East Africa (Taylor et al, 2012). Proof of concept in cassava cv.…”

Section: Introductionmentioning

confidence: 99%

Field Level RNAi-Mediated Resistance to Cassava Brown Streak Disease across Multiple Cropping Cycles and Diverse East African Agro-Ecological Locations

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…To this end, the Virus Resistant Cassava for Africa (VIRCA) (Taylor et al, 2012) project at the Danforth Plant Science Center (St. Louis, MO, USA) recently organized a workshop to assess the risks and consequences of gene flow from transgenic cassava containing CBSV resistance to wild relatives. Based on existing information, this forum concluded that although gene flow is likely to occur, there is only a very small chance that this could lead to a reduction of genetic diversity in the germplasm pool (Hokanson et al, 2016).…”

Section: Regulations Of Genetically Modified (Gm) Crops In Developingmentioning

confidence: 99%

The Search for Resistance to Cassava Mosaic Geminiviruses: How Much We Have Accomplished, and What Lies Ahead

Fondong

2017

Front. Plant Sci.

View full text Add to dashboard Cite

The cassava mosaic disease (CMD), which occurs in all cassava growing regions of Africa and the Indian subcontinent, is caused by cassava mosaic geminiviruses (CMGs). CMGs are considered to be the most damaging vector-borne plant pathogens. So far, the most successful approach used to control these viruses has been the transfer of a polygenic recessive resistance locus, designated CMD1, from wild cassava to cassava cultivars. Further progress in harnessing natural resistance to contain CMGs has come from the discovery of the dominant monogenic resistance locus, CMD2, in some West African cassava cultivars. CMD2 has been combined with CMD1 through genetic crosses. Because of the limitations of the cassava breeding approach, especially with regard to time required to produce a variety and the loss of preferred agronomic attributes, efforts have been directed toward the deployment of genetic engineering approaches. Most of these approaches have been centered on RNA silencing strategies, developed mainly in the model plant Nicotiana benthamiana. Early RNA silencing platforms assessed for CMG resistance have been use of viral genes for co-suppression, antisense suppression or for hairpin RNAs-mediated gene silencing. Here, progress and challenges in the deployment of these approaches in the control of CMGs are discussed. Novel functional genomics approaches with potential to overcome some of the drawbacks of the current strategies are also discussed.

show abstract

“…In view of the difficulties associated with conventional breeding, genetic engineering offers great potential for the rapid transfer of resistance genes to traditional cultivars, bypassing the possibility of the appearance of undesirable traits. Among the available biotechnological approaches, RNA interference (RNAi) or gene silencing technology, also called post-transcriptional gene silencing, offers significant potential for the control of CBSD Prins et al, 2008;Reddy et al, 2009) (Ezezika et al, 2012;Taylor et al, 2012). Three RNAi constructs targeting different parts of the CP of UCBSV-[UG:Nam:04] were generated, which consisted of the 894 nt (FL, full-length), 397 nt N-terminal (NT) and 491 nt C-terminal (CT) portions of the CP and expressed constitutively in the model host N. benthamiana (Fig.…”

Section: Genetic Engineering For Cbsd Resistancementioning

confidence: 99%