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MsC Thesis-Stefanie-final

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MsC Thesis-Stefanie-final

  1. 1. Effects of the parasitic weed Rhamphicarpa fistulosa (Hochst.) Benth. on growth and photosynthesis of its host, Oryza sativa L. Stefanie Pflug (Utrecht University) Supervisors: Lammert Bastiaans, Aad van Ast Examiner: Niels Anten 29 May 2013
  2. 2. Outline Introduction Objectives Materials & Methods Results & Discussion Conclusions Recommendations
  3. 3. Introduction: rice Rice in Sub-Saharan Africa ● increasing demand --> increasing production (FAO 2010), production cannot meet demand --> imports ● rainfed inland valleys as new production areas (Balasubramanian et al. 2007) ● rice is only crop that can be grown there ● available area ● problem: parasitic plant Rhamphicarpa fistulosa
  4. 4. Introduction: Rhamphicarpa fistulosa Facultative hemiparasitic plant Attachment: haustoria (root-xylem) Increasing occurrence in rainfed rice production systems (Rodenburg et al. 2011) ● yield losses: 30-100% (Benin, Tanzania) (Gbèhounou & Assigbé 2003; Rodenburg et al. 2011; Kayeke et al. 2010) --> increasing importance ● little is known about interaction with host Picture: A. van Ast
  5. 5. Introduction: rice --> R. fistulosa Mutual influence host- parasite Source-sink relationship What is the role of host size for R. fistulosa growth? --> profit from larger source or limited by sink? R. fistulosa
  6. 6. Introduction: R. fistulosa --> rice Motive ● MSc thesis A. T. Asfaw (2011) ● rice: reduced growth, R. fistulosa: increased growth ● dry matter loss rice > dry matter gain R. fistulosa Plant dry weight -Rh +Rh Rice -Rice +Rice Rh
  7. 7. Introduction: R. fistulosa --> rice Reasons for this ‘gap’: ● infection at early growth stage of rice --> additive effects over time ● additional effects on rice next to water and solute removal --> photosynthesis?
  8. 8. Objectives 1) Effect of host plant size on parasite growth 2) Effect of parasite on host growth 3) Effect of parasite on host photosynthesis
  9. 9. Materials & Methods Greenhouse Radix Serre April – July 2012 Day/night temperature: 26/23°C, day length: 12 h Arable soil/sand mixture (1:1 by vol.), no fertilizer Daily watering Rice: IR64 R. fistulosa: seeds from Tanzania
  10. 10. Materials & Methods Treatments: 2 rice ages 1 R. fistulosa age & density (30 plants per pot) . . .. . . . .. . . .. . . . . . . .. . +T2 T1 T2 R. fistulosa (control) . . .. . . . .. . . .. . . . . . . .. . . . .. . . . .. . . .. . . . . . . .. . + 3 weeks
  11. 11. Materials & Methods Measurements: R. fistulosa ● Height (average per pot) ● Dry weights: shoot, root Rice ● Growth: height, leaf nr, tiller nr leaf area, dry weight: leaf, stem, root ● Photosynthesis: youngest fully developed leaf -->Light response curves 6 samplings (1-week interval), 4-5 replicates
  12. 12. Results & discussion – R. fistulosa R. fistulosa attached 2 weeks earlier to T2 plants --> actual difference in attachment time: 1 week Earlier attachment -->no final growth advantage: R. fistulosa growth is sink-driven Average plant height (cm) T2 T1
  13. 13. Results & discussion – R. fistulosa R. fistulosa R. fistulosa + rice R. fistulosa + rice control T1 T2
  14. 14. Results & discussion – rice growth Total dry weights T1 T2
  15. 15. Results & discussion – rice growth Total dry weights of controls and associations T1 T2
  16. 16. Results & discussion – rice growth Relative reductions related to R. fistulosa dry weight
  17. 17. Results & discussion – rice growth Further effects: Dry matter allocation Morphology ● Height ● Leaf area ● Leaf nr (T1) ● Tiller nr leaf root stem
  18. 18. Results & discussion – rice growth C T1 C T2
  19. 19. Results & discussion – rice photosynthesis Amax: strong effect Initial light use efficiency: no clear effect Dark respiration: no effect --> photosynthesis only affected at high light levels Photosynthetic-light response curve
  20. 20. Results & discussion – rice photosynthesis Maximum photosynthetic rate T1 T2
  21. 21. Synthesis Final sampling date: ● R. fistulosa dry matter gain ~ 32% of dry matter loss of rice Remaining 68% attributable to: ● subsequent disturbances for host development ● + reductions in photosynthesis Rice Rh
  22. 22. Conclusions R. fistulosa growth is sink- rather than source-driven Effects on rice growth: reduced growth, alterations in dry matter allocation and morphology Size of host plant at infection has influence on severity of effects Effect on rice photosynthesis Sequence of effects: ● 1st reductions in rice biomass production ● 2nd reductions in host photosynthesis
  23. 23. Recommendations Repeat and extend experiment (in progress) ● More infection times and/or densities Individual contribution of the induced effects ● Modelling study with collected data
  24. 24. Thank you for your attention! Questions?
  25. 25. References Asfaw, A.T., 2011. Different aspects of the germination and attachment phase of Rhamphicarpa fistulosa, a newly emerging parasitic weed species. MSc Thesis Wageningen UR, The Netherlands. Balasubramanian, V., Sie, M., Hijmans, R.J., Otsuka, K., 2007. Increasing rice production in Sub-Saharan Africa: challenges and opportunities. Advances in Agronomy 94, 55-133. FAO, 2010. FAO Statistical Databases. http://faostat.fao.org/, accessed on 16- 1-13. Kayeke, J., Rodenburg, J., Mwalyego, F., Mghogho, R., 2010. Incidence and severity of the facultative parasitic weed Rhamphicarpa fistulosa in lowland rainfed rice in southern Tanzania. In: Kiepe, P., Diatta, K., Millar, D. (Eds.), 2nd Africa Rice Congress. Innovation and Partnerships to Realize Africa’s Rice Potential. Africa Rice Center, Cotonou. Ouédraogo, O., Neumann, U., Raynal-Roques, A., Salle, G., Tuquet, C., Dembele, B., 1999. New insights concerning the ecology and the biology of Rhamphicarpa fistulosa (Scrophulariaceae). Weed Research 39, 159–169. Rodenburg, J., Zossou-Kouderin, N., Gbèhounou, G., Ahanchede, A., Touré, A., Kyalo, G., Kiepe, P., 2011. Rhamphicarpa fistulosa, a parasitic weed threatening rain-fed lowland rice production in sub-Saharan Africa – A case study from Benin. Crop Protection 10, 1306-1314.

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