BACTERIAL WILT OF POTATO IN SUB-SAHARAN AFRICA NEW PERSPECTIVES ON AN OLD DISEASE

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2 BACTERIAL WILT OF POTATO IN SUB-SAHARAN AFRICA NEW PERSPECTIVES ON AN OLD DISEASE Kalpana Sharma 1, M.L. Parker 1, B. Ochieng 1, A. Abdurahman 1, J. Kreuze 2, G. Nugundo 3, E. Schulte-Geldermann 1 1 International Potato Center (CIP), Sub-Saharan Africa, Nairobi-Kenya 2 International Potato Center (CIP), Lima-Peru 3 Kenya Plant health inspectorate Service (KEPHIS), Nairobi-Kenya

3 Ralstonia solanacearum on Potato in SSA Notoriously destructive pathogen Numerous economical crops important in tropics: potato, tomato, capsicum, tobacco, eggplant Widespread, essentially endemic in SSA Avoidance/quarantine impossible in many regions Thus needs to be managed

4 Marketable yield (t ha -1 ) Potato Value Chain Bacterial Wilt Yield Losses 35 A B Y = x R 2 = 0.56 (P<0.001) D C Bacterial wilt incedence (Sq root) COUNTRY % loss Burundi Ethiopia Kenya Uganda Bacterial wilt present at all stages of potato value chain Ralstonia is a major cause of poor seed quality Farmers predominately use poor quality seed, & consequently, low yields in SSA (8-12 t/ha)

5 Altitude (m) Survival Proportion Bacterial Wilt, an Increasing Threat Low seed renewal frequency Lack of seed quality control systems Detection of Ralstonia at >3000 masl Climate change in the favor of Ralstonia adaption COUNTRY Ethiopia Kenya Uganda BW prevalence 158 out of 263 farms 128 out of 176 farms 166 out of 288 farms Go Gondar Bacterial wilt reported year Year

6 Bacterial Wilt, an Increasing Threat 372 bp: Phylotype II 280 bp: RS species complex 144 bp: Phylotype I 91 bp: Phylotype III Molecular genotyping of Ralstonia from Eastern Africa East Africa P I P IIA P IIB P III Ethiopia x x Kenya x x x Uganda x x x Rwanda On going Molecular epidemiological studies are underway to understand the movement of Ralstonia within East African region Evidence based findings for policy makers, cross border seed movement Integrated seed health strategy VNTR study of Ralstonia to trace bacterial wilt epidemic in Chencha, Ethiopia

7 Seed Source on Bacterial Wilt On-farm trial in Kenya Three seasons, 8 farms (each a replication) Strategy % bacterial wilt Shangi 100% CF 0 100% PS 4 ± 7 100% RSFS 74 ± 24 20% CF + 80% PS 0 20% CF + 80% RSFS 5.3 ± 7.6 5% SSPT + PS 4 ± 6.9 5% SSPT + RSFS 1 ± 2.3 CF = certified seed PS = positive selection seed RSFS = randomly selected farmers seed SSPT = small seed plot technique

8 Soil Amendments On-station, fully replicated trial, 2 seasons and 2015 Treatment Marketable yield (t/ha) BW Incidence (%) 10³ 10⁷ 10³ 10⁷ Neem 1 t/ha t/ha Control Neem 250 kg/ha Neem 125 kg/ha

9 Rotation Pattern and Best Rotation Crops Bacterial wilt incidence (%) Marketable yield (t/ha) Number of break crops Pre -crops which reduced RS in soil and BW incidence >50% Onion, spring onion, garlic Peru, Ethiopia, Kenya Brassica nigra Ethiopia 25-50% Cabbage, Canola

10 Capturing resistance genes to bacterial wilt from S. commersonii into 4x cultivated genetic background cmm (2n=2x ; 1 EBN) phu 2n=2x ; 2 EBN) F1 (cmm phu ) (2n=3x ; 2 EBN) tbr (2n=4x ; 4 EBN) BC1 tbr (2n=5x ; 4 EBN) EMBRAPABrasil CIPLima INIA-Uruguay BC2 Race 3Bv2 CIPEthiopia Protocol for bacterial wilt resistance implementing a test sensitive method for detection of R. solanacearum in latently-infected tubers Race 1 BC3 Procedures for Generation of Potato Tuber Families from true (botanical) seed

11 Bacterial Wilt Diagnostics NCM-ELISA is the standard test in seed certification LAMP assay CONVENTIONAL/ MULTIPLEX PCR POCKET TEST Kit ImmunoStrip Lateral flow device (LFD) How: Rapid detection of specific DNA or RNA targets; highly sensitive, target specific Users: Public and private seed certification authorities as well as seed producers

12 Concluding Remarks Holistic approach required in BW management combining improvements in: Disease management with suppressive soil amendments/ better rotations Host-plant resistant Disease free seed production and make it accessible to famers Improved diagnostics Positive seed selection for farm saved seed Integrated seed health strategy

13 Ethiopian Institute of Agricultural Research (EIAR) THANK YOU