Based on a review of observations and experiments conducted mainly in Europe and New Zealand, we propose a detailed life-cycle model for R. Its persistence in dairy pastures may also be influenced by plants recruiting from seeds which are formed annually subject to the availability of insect pollinators. The latter enables regeneration after damage inflicted by herbicides, fungi and other control agents, and facilitates lateral spread and asexual reproduction. Its persistence appears to be due in part to the production of a blistering agent, protoanemonin, which deters grazing animals, combined with evolved resistance to herbicides and a resilience imparted by a stout rhizome supporting dormant axillary buds. In New Zealand, it persists in dairy pastures throughout the country, despite the annual use of herbicides, causing a loss in the national yield of milk solids estimated at NZ$156 million in the 2001–2002 milking season. ![]() acris is widespread in pastures across Europe. read more read lessĪbstract: Sclerotinia sclerotiorum is an important pathogen of many crop plants which also infects wild hosts The population structure of this fungus was studied for different crop plants and Ranunculus acris (meadow buttercup) in the UK using eight microsatellite markers and sequenced sections of the intergenic spacer (IGS) region of the rRNA gene and the elongation factor 1-alpha (EF) gene A total of 228 microsatellite haplotypes were identified within 384 isolates from 12 S sclerotiorum populations sampled in England and Wales One microsatellite haplotype was generally found at high frequency in each population and was distributed widely across different hosts, locations and years Fourteen IGS and five EF haplotypes were found in the 12 populations, with six IGS haplotypes and one EF haplotype exclusive to buttercup Analysis of published sequences for S sclerotiorum populations from the USA, Canada, New Zealand and Norway showed that three of the IGS haplotypes and one EF haplotype were widely distributed, while eight IGS haplotypes were only found in the UK Although common microsatellite and IGS/EF haplotypes were found on different hosts in the UK, there was evidence of differentiation, particularly for one isolated population on buttercup However, overall there was no consistent differentiation of S sclerotiorum populations from buttercup and crop hosts Sclerotinia sclerotiorum therefore has a multiclonal population structure in the UK and the wide distribution of one microsatellite haplotype suggests spatial mixing at a national scale The related species S subarctica was also identified in one buttercup population. Ongoing naturalisations, from an existing pool of exotic plant species estimated. The aggregate cost of pastoral weeds to the New Zealand economy is estimated to be NZ$1.2 billion per annum, based on an analysis made in 1984, but this analysis is hampered by a lack of both objective data on the impacts of weeds on pastoral production and an accurate and comprehensive national census of the main problem species. While 34 of these pastoral weeds are currently being managed under Regional Pest Management Strategies, 15 of these regionally managed species are apparently un‐researched in New Zealand, implying that their management does not have a scientific basis. ![]() Judging from their occurrence in scientific papers published in the proceedings of the New Zealand Plant Protection Society, 65 of these species are, or have been considered historically, to be significant pastoral weeds. ![]() Abstract: Currently there are some 187 plant species, almost all exotic in origin, occurring as “weeds” in pastures in New Zealand.
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