title: Proliferation of the biocontrol agentFusarium oxysporumf. sp.strigaeand its impact on indigenous rhizosphere fungal communities in maize under different agro-ecologies.
abstract: Our objectives were to (1) monitor the proliferation of the biocontrol agent (BCA)Fusarium oxysporumf. sp.strigaestrain "Foxy-2", an effective soil-borne BCA against the parasitic weedStriga hermonthica, in the rhizosphere of maize under different agro-ecologies, and (2) investigate its impact on indigenous rhizosphere fungal community abundance and composition. Field experiments were conducted in Busia and Homa Bay districts in western Kenya during two cropping seasons to account for effects of soil type, climate, growth stage and seasonality. Maize seeds were coated with or without "Foxy-2" and soils were artificially infested withS. hermonthicaseeds. One treatment with nitrogen rich organic residues (Tithonia diversifolia) was established to compensate hypothesized resource competition between "Foxy-2" and the indigenous fungal community. Rhizosphere soil samples collected at three growth stages (i.e., EC30, EC60, EC90) of maize were subjected to abundance measurement of "Foxy-2" and total indigenous fungi using quantitative polymerase chain reaction (qPCR) analysis. Terminal restriction fragment length polymorphism (TRFLP) analysis was used to assess potential alterations in the fungal community composition in response to "Foxy-2" presence. "Foxy-2" proliferated stronger in the soils with a sandy clay texture (Busia) than in those with a loamy sand texture (Homa Bay) and revealed slightly higher abundance in the second season. "Foxy-2" had, however, only a transient suppressive effect on total indigenous fungal abundance which ceased in the second season and was further markedly compensated after addition ofT. diversifoliaresidues. Likewise, community structure of the indigenous fungal community was mainly altered by maize growth stages, but not by "Foxy-2". In conclusion, no adverse effects of "Foxy-2" inoculation on indigenous fungal rhizosphere communities were observed corroborating the safety of this BCA under the given agro-ecologies.
authors.affiliation: Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Stuttgart, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Zimmermann
authors.affiliation: Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Stuttgart, Germany.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Musyoki
authors.affiliation: Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Stuttgart, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Cadisch
authors.affiliation: Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Stuttgart, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Rasche
keywords: 18S rDNA; Fusarium oxysporum f.sp. strigae; Quantitative PCR; TRFLP analysis; maize