msc thesis-stefanie-final
TRANSCRIPT
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
Outline
� Introduction
� Objectives
� Materials & Methods
� Results & Discussion
� Conclusions
� Recommendations
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
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
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
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 dryweight
-Rh +Rh
Rice
-Rice +Rice
Rh
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?
Objectives
� 1) Effect of host plant size on parasite growth
� 2) Effect of parasite on host growth
� 3) Effect of parasite on host photosynthesis
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
Materials & Methods
Treatments: 2 rice ages
1 R. fistulosa age & density (30 plants per pot)
. . .. .. . .. . ... . . . .. . .. .
+T2 T1
T2
R. fistulosa (control)
. . .. .. . .. . ... . . . .. . .. .
. . .. .. . .. . ... . . . .. . .. .
+
3 weeks
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
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
Results & discussion – R. fistulosa
R. fistulosa R. fistulosa + rice R. fistulosa + rice
control T1 T2
Results & discussion – rice growth
Total dry weights
T1 T2
Results & discussion – rice growth
Total dry weights of controls and associations
T1 T2
Results & discussion – rice growth
Relative reductions related to R. fistulosa dry weight
Results & discussion – rice growth
� Further effects:
Dry matter allocation Morphology
● Height
● Leaf area
● Leaf nr (T1)
● Tiller nr
leaf
root
stem
Results & discussion – rice growth
C T1 C T2
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
Results & discussion – rice photosynthesis
Maximum photosynthetic rate
T1 T2
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
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 severityof effects
� Effect on rice photosynthesis
� Sequence of effects:
● 1st reductions in rice biomass production
● 2nd reductions in host photosynthesis
Recommendations
� Repeat and extend experiment (in progress)
● More infection times and/or densities
� Individual contribution of the induced effects
● Modelling study with collected data
Thank you for
your attention!
Questions?
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.