UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Allelopathic influence of tall hedge mustard (Sisymbrium loeselii L.) and spotted knapweed (Centaurea maculosa Lam.) on arbuscular mycorrhizal fungi Bainard, Luke D.

Abstract

Many exotic weeds interfere with other species by releasing allelochemicals into the environment that have a negative effect on their growth and distribution. Allelochemicals can have a direct influence on plant growth and/or indirect influence by disrupting interactions between plants and soil organisms, such as arbuscular mycorrhizal (AM) fungi. The goal of this research was to explore the allelopathic influences of the exotic weeds tall hedge mustard (Sisymbrium loeselii L.) and spotted knapweed (Centaurea maculosa Lam.). The allelopathic potential of tall hedge mustard was assessed using aqueous root and shoot extracts in seed germination and seedling growth bioassays. Aqueous tall hedge mustard root and shoot extracts strongly inhibited germination and growth of bluebunch wheatgrass, Idaho fescue, and spotted knapweed. Glucosinolate (GSL) analysis of tall hedge mustard tissues revealed the presence of two major GSLs (isopropyl GSL and sec-butyl GSL) and four indolylic GSLs. The degradation products of the two major GSLs (isopropyl isothiocyanate [ITC] and sec-butyl ITC) were identified in tall hedge mustard aqueous root and shoot extracts. Commercially available isopropyl ITC and sec-butyl ITC inhibited seed germination and seedling growth, suggesting their role in the allelopathic influence of tall hedge mustard. Tall hedge mustard aqueous extracts and ITCs incorporated into an agar medium inhibited Glomus intraradices Shenck & Smith spore germination and hyphal growth. Tall hedge mustard aqueous extracts strongly inhibited spore germination and hyphal growth of G. intraradices. Isopropyl ITC and sec-butyl ITC inhibited spore germination and hyphal growth, with the former exhibiting a stronger effect. Tall hedge mustard infestations were also found to reduce the A M inoculum potential of soil. The A M colonization and total biomass was reduced in bluebunch wheatgrass and spotted knapweed plants growing in tall hedge mustard infested compared to noninfested soil. Spotted knapweed is known to produce two major allelochemicals, (±)-catechin and cnicin. Both allelochemicals inhibited Glomus intraradices spore germination, and cnicin also inhibited the hyphal growth, suggesting that these allelochemicals may be involved in the inhibitory effect spotted knapweed has on A M fungi. Results of this study show that tall hedge mustard and spotted knapweed both produce allelochemicals that have the potential to directly and/or indirectly inhibit the growth of neighboring species and their A M fungal associates.

Item Media

Item Citations and Data

Rights

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.