Characterisation of microbial communities associated with potato cyst nematodes in a suppressive soil and the bicontrol potential of selected isolates

Jones, Amanda Louise

Abstract

Potato cyst nematodes Globodera pallida and G. rostochiensis (PCN) pose a growing threat to global potato production. As chemical nematicides are increasingly removed from market, novel, environmentally sound methods are needed to manage PCN populations. In the context of developing microbial biocontrol for PCN, this work used a soil naturally suppressive to PCN: 1). to gain fundamental knowledge of microbial communities developing on PCN cysts; 2). to investigate how such communities may be linked to egg viability and hatch; and 3). to assess the ability of a range of fungi and bacteria to control PCN in vitro and in vivo.

A pot experiment was used to verify PCN suppression in an intensively cropped potato field soil from Shropshire. Potato cyst nematodes (G. pallida) had a significantly lower egg viability when used to inoculate potatoes grown in soil taken from the Shropshire field site in comparison to potatoes frown in a conducive soil (49% reduction). Transfer of suppression was shown using 10% suppressive soil (90% conducive soil), resulting in significantly lowered viable eggs g-1 soil, compared to conducive soil pots (78% reduction).

Using a soil microcosm experiment, G. pallida cysts were buried in untreated or autoclaved (i.e., altered microbial community) suppressive soil for four time periods. Resulting egg hatch was reduced by >77% in week 48 for both treatments. Residual egg viability was significantly lowered after 20 weeks for cysts buried in both soils (67% and 81% reductions for autoclaved and untreated soils, respectively, compared to unburied control cysts). Next-generation sequencing revealed that buried cysts had distinct bacterial and fungal communities, compared to their surrounding soils. Cyst communities changed depending on soil treatment (untreated vs. autoclaved) and incubation time. Indicator taxa, including Michrodochium bolleyi and Gibellulopsis nigrescens, were found to define soil communities for both treatments, indicating that microorganisms possibly responsible for reducing egg viability and hatch, survived autoclaving.

This study contributed new knowledge towards microorganisms associated with PCN, particularly in the context of a suppressive soil. Overall, findings suggest that PCN antagonism in suppressive soil requires a complex community of PCN suppressive microorganisms and potentially several PCN suppressive mechanisms, both on the cyst and in the surrounding soils. Future PCN biocontrol studies should focus on microbial interactions of suppressive soils beyond direct parasitism, and further understanding of the functional attributes of microbial communities that reside on and inside of cysts.

Citation

Jones, A. L. Characterisation of microbial communities associated with potato cyst nematodes in a suppressive soil and the bicontrol potential of selected isolates. (Thesis). Edinburgh Napier University

• Thesis Type: Thesis
• Deposit Date: Sep 3, 2024
• Publicly Available Date: Sep 3, 2024
• DOI: https://doi.org/10.17869/enu.2024.3789821
• Award Date: Jul 3, 2024