Author
Graeme Bourdôt
graeme.bourdot@agresearch.co.nz
New Zealand Institute for Bioeconomy Science Limited – AgResearch group, Lincoln, New Zealand
Coauthors
Jonty Mills, Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln, Canterbury, New Zealand
Jonathan Hadipurnomo, New Zealand Institute for Bioeconomy Science Limited – AgResearch group, Lincoln, New Zealand
Seona Casonato, Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln, Canterbury, New Zealand
Laura Villamizar, New Zealand Institute for Bioeconomy Science Limited – AgResearch group, Lincoln, New Zealand
Abstract
The fungus Sclerotinia sclerotiorum shows strong potential as a bioherbicidal agent for the selective control of pasture weeds such as Cirsium arvense (Californian thistle) and Ranunculus acris (giant buttercup). Mycelium-colonised solid substrates have proven effective but are costly and difficult to scale. This study identified the fermentation conditions necessary for microsclerotia (MS) production by S. sclerotiorum, offering an economical and scalable alternative. Microsclerotia are compact, melanised propagules with desiccation tolerance, storage stability, and strong infective potential. Although MS have been produced in liquid media by other fungi, this is the first report for S. sclerotiorum. Seven liquid media with different nutrient compositions were evaluated for MS induction by a strain of S. sclerotiorum isolated from C. arvense in a pasture in Canterbury, New Zealand. One medium supported consistent formation, yielding 4 × 10³ MS/mL after 14 days of shake-flask fermentation at 300 rpm. The MS were spherical, darkly pigmented, and 100–300 μm in diameter. When tested on excised host tissues, the MS caused extensive necrotic lesions significantly larger than those produced from natural sclerotia inoculum. Fermentation conditions were later optimised achieving a yield 5 times higher (2 x 104 MS/mL). Our study established a scalable method for producing highly viable S. sclerotiorum microsclerotia, to support the development of a cost-effective bioherbicide.
Keywords
clerotinia sclerotiorum
microsclerotia
biocontrol
bioherbicide
fermentation
Highlights
Microsclerotia are a cost-effective solution for Sclerotinia-based bioherbicides
Fermentation was optimised increasing microsclerotia yields.
S. sclerotiorum microsclerotia effectively infect target pasture weeds