PhytoFrontiers (Jan 2021)
Role and In Vivo Localization of Fusarium oxysporum f. sp. strigae and Bacillus subtilis in an Integrated Striga hermonthica Biocontrol System
Abstract
To improve the efficiency of Striga hermonthica biological control in the context of an integrated biocontrol system, the role/impact of coinoculating the mycoherbicide Fusarium oxysporum f. sp. strigae (Fos) with a plant growth promoting rhizobacterium, Bacillus subtilis isolate GB03, on S. hermonthica attachment and sorghum biomass was investigated. Fos isolates (Foxy-2, FK3) and GB03, including Trichoderma viride (IMB12098 strain) as reference, were applied as single and combined treatments to S. hermonthica-infested rhizoboxes with sorghum as the host crop. In vivo localization/interaction of Fos and GB03 in S. hermonthica was monitored by fluorescent gene expression of transformed Fos and transformed GB03. Combined treatments of FK3 + GB03 and Foxy-2 + GB03 increased sorghum aboveground dry biomass (P < 0.05), but not IMB12098 + GB03. None of the combined treatments suppressed S. hermonthica attachment. Single treatments of FK3 and GB03 increased sorghum aboveground dry biomass (P < 0.05), but Foxy-2 and IMB12098 did not. Only FK3, of all single treatments, suppressed S. hermonthica attachment (P < 0.05). GB03 promoted sorghum yield when applied alone or combined with Fos (P < 0.05). Fos penetration of S. hermonthica through trichome entry was revealed. Although Fos, either as sporal (conidia) or vegetative form (mycelium), co-occupied common ecological niches with GB03 (they colocalize) in diseased S. hermonthica shoots, mainly in flavonoid-rich regions. Nevertheless, GB03 thwarted Fos suppressive activity against S. hermonthica attachment. In the given setup, coinoculation of Fos with GB03 presented no added advantage in suppressing the incidence of the sampled S. hermonthica.[Figure: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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