MsC Thesis-Stefanie-final
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1) The study examined the effects of the parasitic weed Rhamphicarpa fistulosa on the growth and photosynthesis of its host, rice. 2) R. fistulosa growth was found to be driven by sink capacity rather than source size, as earlier attachment to larger rice plants did not confer a growth advantage. 3) R. fistulosa infection severely reduced rice growth, dry matter allocation, and morphology. It also negatively impacted rice photosynthesis, especially at high light levels. 4) The reductions in rice biomass production and photosynthesis contributed to the majority of dry matter loss in rice, beyond what was gained by R. fistulosa.
MsC Thesis-Stefanie-final
- 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. Outline Introduction Objectives Materials & Methods Results & Discussion Conclusions Recommendations
- 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. 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. 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. 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. 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. 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. 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. Materials & Methods Treatments: 2 rice ages 1 R. fistulosa age & density (30 plants per pot) . . .. . . . .. . . .. . . . . . . .. . +T2 T1 T2 R. fistulosa (control) . . .. . . . .. . . .. . . . . . . .. . . . .. . . . .. . . .. . . . . . . .. . + 3 weeks
- 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. 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. Results & discussion – R. fistulosa R. fistulosa R. fistulosa + rice R. fistulosa + rice control T1 T2
- 14. Results & discussion – rice growth Total dry weights T1 T2
- 15. Results & discussion – rice growth Total dry weights of controls and associations T1 T2
- 16. Results & discussion – rice growth Relative reductions related to R. fistulosa dry weight
- 17. Results & discussion – rice growth Further effects: Dry matter allocation Morphology ● Height ● Leaf area ● Leaf nr (T1) ● Tiller nr leaf root stem
- 18. Results & discussion – rice growth C T1 C T2
- 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. Results & discussion – rice photosynthesis Maximum photosynthetic rate T1 T2
- 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. 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. 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. Thank you for your attention! Questions?
- 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.