Documents

MSc-thesis Luuk van Dijk

Over the last decades rice (Oryza spp) became more important as a staple food crop for the African continent. In two decades, the locally produced rice in Africa doubled to almost 30 Mt in 2013. Still, the local production is insufficient to meet local demand and this particularly holds for Sub-Saharan Africa (SSA). Rice yields in SSA pertain to the lowest in the world. One of the major constraints accountable for these low yields are weeds. The parasitic weeds Striga asiatica and Rhamphicarpa fistulosa can cause devastating yield loses in SSA rice production. Recent field observations suggest that the presence of parasitic weeds influences the competitive relations between rice and non-parasitic (or ordinary) weeds. In the presence of S. asiatica the competitiveness of ordinary weeds was increased, whereas in the presence of R. fistulosa the ordinary weeds were further suppressed. Two pot experiments, carried out under greenhouse conditions, were used to study how the competitive relations between rice and the ordinary weed Mitracarpus villosus was affected by the presence of either S. asiatica or R. fistulosa. Plant dry biomass was used as a measure for the competitive effects. S. asiatica caused significant reductions in total pot biomass compared to pots with rice alone. Such a reduction was however not observed if next to rice also the M. villosus was present. This absence of a reduction in total pot biomass was not because the ordinary weed filled the gap that was created through the negative effect of the parasite on its rice host, rather rice biomass did not decrease in the rice-ordinary weed mixture. Emergence of S. asiatica in this mixture was lower, and this might be accountable for the minor effect of the parasite on the host. It is suggested that the root system of the ordinary weed might have disturbed the establishment of a connection between the host and the parasite, resulting in a reduced emergence of S. asiatica. R. fistulosa reduced rice biomass much more strongly than S. asiatica. In the rice-weed mixture, the ordinary weed was not able to profit from the reduced growth of the rice plant, as R. fistulosa grew fiercely and developed into a strong competitor. Consequently, the competitive ability of the ordinary weed, just as that of the rice plant, was strongly decreased. The experiments clearly show that the presence of a parasitic weed affects the growth and competitive relation between rice and ordinary weeds both directly and indirectly. The outcome of this complex multi-species interaction depends a lot on the parasitic weed species. R. fistulosa showed to be a damaging pest and utilized its ability to parasitize rice to gain a stronger competitiveness against the developed into the species dominating not only the rice, but also the ordinary weed. In case of S. asiatica, the ordinary weed reduced the infestation level of the parasitic weed and consequently the competitive relation between rice and the ordinary weed remained relatively undisturbed.

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Tropenzentrum presentation Jonne Rodenburg

Tropenzentrum presentation Jonne Rodenburg - 7 July 2014: "Multi-disciplinary and multi-stakeholder approaches in crop protection – the case of parasitic weeds in rainfed rice systems in Africa"

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Presentation Stella Kabiri (subproject 1)

Presentation by Stella Kabiri during the Parasite mid-term workshop, 17 June 2014

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Presentation Jonne Rodenburg (subproject 2)

Presentation by Jonne Rodenburg during the Parasite mid-term workshop, 17 June 2014

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Presentation Simon N’cho (subproject 3)

Presentation by Simon N'cho during the Parasite mid-term workshop, 17 June 2014

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Presentation Marc Schut (subproject 4)

Presentation by Marc Schut on postdoc project during the Parasite mid-term workshop, 17 June 2014

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Brochure: Rapid Appraisal of Agricultural Innovation Systems (RAAIS)

RAAIS is a participatory, diagnostic tool for integrated analysis of complex agricultural problems. RAAIS has been developed and tested to identify and analyze opportunities for dealing with parasitic weeds in rainfed rice production in Tanzania and Benin

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Innovation Platform Practice Briefs

Developed during a Humidtropics Writeshop in June 2013. The 13 short papers include background on various aspects of innovation platforms, such as their facilitation, monitoring and evaluation, communication, the role of research, etc.

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An ex-ante impact assessment of a Striga control programme in East Africa

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Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co-occur in rain-fed rice?

Power point presentation by Stella Kabiri on 12 December 2013 entitled: "Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co-occur in rain-fed rice?"

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