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.