Identification of RYMV resistant varieties in West Africa Y. Séré, Africa Rice Center

1. Identification of RYMV resistant varieties in West Africa Y. Séré, Africa Rice Center A.A. Sy, M. Sié, R.G. Guéi, K.M. Miezan, A. Onasanya, A. Afolabi, S. Akator, M.M. Coulibaly, A. Hamadoun, A.Y. Sido, A. Basso, E.M. Abo, S. Sara, F. Cissé Africa Rice Congress 31 July – 4 August 2006, Dar es Salaam, Tanzania

2. OUTLINE Background Methodology Results Conclusion and way forward

3. Background • The early 90th RYMV spread in WA countries • Hindered the efforts of intensification • Reproduced Tungro scenario in Asia • Main causes (Ghesquiere et al., 2000): • Development of irrigation • Release of susceptible varieties from Asia • Development of transplanting (Office du N)

4. Background • In Cote d’Ivoire (Nguessan et al., 1999, Yoboue et al., 2001) • Yield losses from 20 to 60% reported • Many farmers suffered complete crop failure • In Mali (Coulibaly et al, 2001; Hamadoun et al, 2001) • Estimated losses: 187 millions CFA in O du N • Selingue and inland Vallee arround Sikasso region also highly infected

5. Background • In Niger (Reckauss and Adamou, 1986) • Yield losses between 59 and 68 % • Hot spots: Say1, Saga, Diomana, Bonfeba • Potential yield gap in the WA region for 1998-2000= 329,000 metric tones of rice (Pinto, 2000)

6. Background Varietal resistance is the main component of an Integrate management of RYMV

7. Background • However resistance was found only within: • African Oryza species (glaberrima, longistaminata) and traditional African upland rice varieties such as OS 6, LAC 23, and Moroberekan (Singh and Paul, 1995) • One indica Gigante (Tete) (Ndjiondjop, 1999) • None was suitable for intensive irrigated rice production system

8. Background • Poor diversity of varieties used in West Africa (Séré and Sy, 1994) : • BG 90-2 (Mali), IR 1529-680-3 (Niger), Bouake 18 (Cote d’Ivoire), ITA 212 (Nigeria) and Jaya (Senegal) grown in 90 % of the superficies • They are all highly susceptible to RYMV

9. Background • Therefore is it possible while looking for a long-term solution from breeding programs, • to look for resistant/tolerant varieties • that yield at least as • the susceptible released ones?

10. Methodologies 1. Screening for RYMV resistance

11. Methodologies • First set = 222 varieties collected from • IRRI (as IR 47686-15-1) • NARS (for instance FKR 44, DJ 12-119) • CIAT (CT 9153-11-7-1-1) • Second set japonica from • IRRI (siter lines of IR 47686-15-1) • USA (Norin, Litton, Leah) through INGER

12. Methodology 2.Yield trial for those that perform as well as Moroberekan or Gigante (Tete) ANOVA and mean comparison of yield components and yield

13. Methodology • 3.Special case of japonica: Yield trial under different sowing densities • 20 cm x 20 cm • 20 cm x 10 cm • Continuous line (8 g / m2) • Normal transplanting

14. Methodology • 4. On-farm test of the best candidate for replacement in • Niger • Mali • Côte d’Ivoire • Guinea On-farm test at Selingue (Mali)

15. Results 1.Identification of potential of candidates  First set screened at Gagnoa in CI

16. Results • Some of them were sent in Tanzania where the • following three were found resistant to RYMV • H-232-44-1-1 • H-234-18-1-1-1 • GIGANTE (TETE)

17. Results first generation of japonica

18. Results Second generation of japonica: Reaction of IR 47686 sister lines

19. Results Checking the performance of progenies from a cross between Bouake 189 and Gigante

20. Bouake 189 Gigante (Tete) X 1 2 3 4 1 2 3 4 1 = Control 2 = Part of one leaf 3 = Entire one leaf 4 = The whole plant 1 2 3 4 Influence of inoculum pressure on a susceptible and resistant varieties and one of their progeny

21. Results 2.Performance of selected candidates  First set 16 var. in 6 localities in Côte d’Ivoire

22. Results CT 9153-11-7-1-1 and PNA 647F4 are the best candidate performing as Bouake and • even more in some localities • even in low RYMV pressure * Mean of 4 replications **RYMV score (1-9)

23. Results IR 1529-680-3 IR 62161-22-1-2-1-1 BG 90-2 IR 62161-22-1-2-1-1 Photo 5 : CT 9153-11-7-1-1 dans le bas-fond de Natio en Côte d’Ivoire CT 9153-11-7-1-1 and PNA 647F4 showing some tolerance to iron toxicity in CI

24. Results Same tendencies in 3 localities in Mali Kayao in Office du Niger Selingue * Mean of 3 replications **RYMV score (1-9)

25. Results  first generation of japonica(15 entries)

26. Results Effect of planting method and densities on the yield of two varieties

27. Results  second generation of japonica 1 = mean of 4 replications ** = significant at 1% level * = significant at 5% level ns = not significant

28. Results 2.On farm test of the performing candidates  In Mali at Sélingué in 2004 PNA 647F4-56 PNA 647F4-56 was selected by visiting farmers

29. Results  In Mali at Niono (in 2005) Visiting farmers chosen PNA647 F4-56 and BK x GG116 but: BK x GG116 cycle appeared too long for double cropping

30. Results  In Guinea at Seredou (in 2005)

31. Conclusion and way forward 1.The best materials identified were:  PNA 647F4-56 and CT 9153-11-7-1-1 (indica)  IR 47686-15-1-1 and IR 47686-18-7-2 (japonica) 2.The highly resistance gene have been transferred from Gigante into the susceptible Bouake 189 by WARDA providing another candidates 3. But some questions need clarifications for long term solution:

32. Mainly when looking at disease progression Bouake model PNA model NERICA model

33. Is such a reaction • Adult plant resistance mechanism? • Environment-dependant? • Strain-dependant? What is its the genetic background? •  The highly resistance gene found so far is it the unique monogenic resistance to RYMV?

34. Thank to DFID/CPP Japan IRRI & CIAT

35. Thank you Merci Asante sana Obrigado Melesi