Some highlights of CBSD research at NaCRRI National Cassava Research Programme National Crops Resources Research Institute (NaCRRI), NARO Key Milestones in history of CBSD On-going CBSD research activities Emerging ideas on CBSD Where we are located Hellen Apio NaCRRI, Namulonge Year Key Historic Highlights 1935 1st report in Tanzania (Storey, 1936) 1945 1st report in UG, introduced from TZ (Jameson, 1964) 1946 Sap transmission (Lister, 1959) 1950 Details of symptoms, report in Kenya (Nichols, 1950) 1946 Virus-like particles under EM ( Kitajama & Costa, 1964) 1994 CBSD re-appears in Uganda (Thresh et al., 1994) 1995 Tolerance identified in a landrace in TZ (Hillocks et al.,) 2000 Re-appears in Kenya (Munga et al., unp.) 2000 Gen. Ipomovirus, Fam. Potyviridae (Monger et. al., 2001a) 2000 PCR diagnostic test (Monger et. al., 2001b) 2004 CBSD re-emerges in Uganda (Alicai et al., 2007) 2005 1st National Consultative Workshop on CBSD 2005 CBSV transmission by whiteflies Bemisia tabaci (Maruthi et al., 2005) 2009 Two genetically distinct strains of CBSV (Mbazibwa et al. 2009) 2009 1st Complete CBSV genome sequence (Mbazibwa et al. 2009) 2009 Evidence of CBSV transmission by spiralling whiteflies (Mware et al.,2009(b)) 2009 1st CBSV antibodies for use in ELISA (Winter et al., 2009) 2010 CBSD International Workshop in Uganda 2005 Districts surveyed 18 2007 Districts with CBSD 4 Districts surveyed 20 CBSD Incidence in Uganda 2009 2008 Districts with CBSD 8 Districts surveyed 25 Districts with CBSD 18 “Biotechnology Applications to Combat Cassava Brown Streak Disease” (2010 – 2013): Tanzania, Uganda & IITA Improve existing markers for CBSD field resistance from Namikonga: Fine map genomic regions showing QTLs; transcriptome sequencing; Generate SNP resources; Develop new markers and breeding resources for new sources of field resistance to CBSD: markers linked to new sources of resistance; (AR400-6; NDL06/132) Test strain x genotype effects; (AR40-6, Mkombozi, Muzege, Mufarasa, I96/1089A) Generate partial inbred lines -12 parental lines Utilize markers in Tanzania and Uganda to begin breeding new CBSD-resistant cultivars suitable for the region: Uganda: Namikonga X (TME14, MM96/4271, NASE12, MH97/2961) Tanzania Namikonga X (AR37-80; Mreteta; Libaga; Albert) Test a transgenic approach to controlling CBSD: 7 siRNA lines derived from FL 7 siRNA lines derived from N-terminal 2 non-trangenic (TMS60444 & Ebwanatereka) Towards understanding and developing varieties resistant to cassava brown streak virus disease in Uganda Determine the genetic diversity and population structure of CBSV in Uganda; Isolates from Uganda + controls Symptom variability Determine the rate of spread and impact on growth of CBSV infection in Cassava: 3 locations; 3 varieties inoculation levels Identify sources of CBSD resistance genes from both local and introduced cassava germplasm: 116 genotypes field evaluated 116 genotyped with 30 SSR markers Understand the genetics of CBSD: Genetic analysis of F1s S1 evaluations; mapping in one family Regional project under CRCoE • Four target countries: Uganda, Kenya, Tanzania & Ethiopia • Concept of genetic stocks – Genetic stocks that combine CMD & CBSD resistance – Genetic stocks that combine CMD & CBSD resistance with beta carotene – Genetic stocks that combine CMD & CBSD resistance with earlybulking – Genetic stocks that combine CMD, CBSD & whitefly resistance • Establishment of core collection • Validation of CBSD markers associated with different sources of resistance • Advance back-up cassava breeding materials Emerging ideas on CBSD • Breeding programmes vision – “Superb” variety – Can be achieved or missed- several examples – If missed go with best alternative stabilize/ increase production – Meantime Tolerance + Phytosanitation for CBSD • Back-up CBSD resistance breeding; reflect on the past – Wild relatives; phenomenal progress made between 1930s to 1950s – Cultivated cassava; post-independence tolerance/ partial resistance – All countries to evaluate available germplasm in hot spots • Fine-tuning CBSD evaluations protocols – Standardize phenotypic scores; leaf vs stem symptoms! – Combine quantitative with qualitative measures – Increasing evidence of genotype x strain interaction; story of the 8 clones Thank you