Effects of Contrasting Soil Types, Organic Fertilisation and Striga Presence on the Abundance of the Biocontrol Agent Fusarium oxysporum F.sp. strigae in Soils
Judith Zimmermann1, Alan Watson2, Markus Gorfer3, Georg Cadisch1, Frank Rasche1
1University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Germany
The parasitic weed species Striga hermonthica is one of the major constraints to cereal production in sub-Saharan Africa affecting the livelihood of about 100 million people. Striga lives parasitically on cereal crops such as millet, sorghum, maize, rice and sugar cane where it can lead to up to 100% crop loss in the field. The soil-borne biocontrol agent (BCA) Fusarium oxysporum f.sp. strigae (acronym: Foxy 2) has shown superior suppression ability of all growing stages of the weed Striga and seems to be a promising control tool for the African farmers. For the wide spread application in the field it is necessary to assess the control stability and therefore the persistence of the BCA under contrasting environmental conditions to investigate necessary re-inoculation times. Therefore a molecular detection tool based on quantitative polymerase chain reaction (qPCR) was developed to specifically quantify Foxy 2 in soil samples. In the presented study, a rhizobox experiment was performed with a Striga tolerant maize variety under controlled conditions in a climate chamber. Since the persistence of Foxy 2 can vary under different soil conditions and with presence or absence of the weed Striga we have included two contrasting tropical soil types, organic fertilisation with Tithonia diversifolia and Striga presence and absence in the experimental design. Foxy 2 was introduced via seed coating of the maize seed with 1.15*105 colony forming units per seed. Rhizosphere soil samples were obtained 14, 28 and 42 days after planting and further analysed on the abundance of Foxy 2.
Keywords: Biological control agents, Fusarium oxysporum f.sp. strigae, Striga hermonthica
Contact Address: Judith Zimmermann, University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Stuttgart, Germany, e-mail: judith.zimmermann2gmx.de