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.