Abstract
Fusarium oxysporum f.sp. strigae (Fos) is an effective biocontrol agent (BCA) against the parasitic weed Striga hermonthica. It acts in the rhizosphere of several tropical cereals, where it may interfere with indigenous microbial populations. To test this impact, we assessed in a 2-season field experiment at two contrasting tropical agro-ecological sites the response of nitrifying and total indigenous prokaryotic communities in the rhizosphere of maize to the exposure of the Fos-BCA “Foxy-2”. At early leaf development (EC30), flowering (EC60) and senescence (EC90) stage of maize, rhizosphere samples were obtained and subjected to community analysis of bacterial and archaeal amoA (ammonia monooxigenase) (AOB, AOA) and 16S rRNA genes. Abundance and community composition of all studied genes were predominantly influenced by soil type, crop growth stage and seasonality. No major effect of “Foxy-2” was found. Notably, total archaeal community relative to bacteria dominated in the clayey soil which was linked to its strong soil organic carbon (SOC) background. Compared to bacterial nitrifiers, domination of nitrifying archaea increased towards senescence stage which was explained by biochemical differences in organic resource availability between the crop growth stages. During the short rain season, the higher archaeal abundance was mainly driven by increased availability of organic substrates, i.e., extractable organic carbon. Our findings suggested that archaea had greater rhizosphere competence than “Foxy-2” in soils with higher clay and SOC contents. We verified that “Foxy-2” in maize rhizospheres is compatible with nitrifying prokaryotes under the given environments, in particular in clayey soils dominated by archaea.
Highlights
The fungal strain Fusarium oxysporum f.sp strigae (“Foxy-2”) has been acknowledged as a potent biological control agent (BCA) against Striga hermonthica which is parasitic to several cereals cultivated in Sub-Saharan Africa (Schaub et al, 2006; Venne et al, 2009; Elzein et al, 2010)
A clear distinction of archaeal abundance was revealed in response to the three crop growth stages, where EC90 showed generally highest 16S RNA archaeal gene copies during the short rains (SR) season, while archaeal abundance was dominating during EC60 during the long rains (LR) season (P > 0.001) (Fig. 2a and b)
An interaction was found between factors “Season” and “Site”, where higher bacterial 16S rRNA gene copies were measured at Busia during SR season (P < 0.001) (Table 2 and Fig. 2c)
Summary
The fungal strain Fusarium oxysporum f.sp strigae (“Foxy-2”) has been acknowledged as a potent biological control agent (BCA) against Striga hermonthica which is parasitic to several cereals cultivated in Sub-Saharan Africa (Schaub et al, 2006; Venne et al, 2009; Elzein et al, 2010). The rhizosphere is a hot spot of microbial activities interacting with plants (Grayston et al, 1998), but no understanding is currently available regarding the interactions of “Foxy-2” with indigenous microorganisms colonizing the roots of cereals and environmental factors including site-specific soil and climatic conditions. This is of particular relevance since “Foxy-2” is often delivered via seed coating and proliferates subsequently along the roots where it directly interacts with other rhizosphere organisms.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
