Bryan, Stephanie and Roberts, Mike and Wilson, Kenneth (2017) The ecological impacts of a novel nematode control agent. PhD thesis, Lancaster University.
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Abstract
Plant-parasitic nematodes are prevalent in many soils and impose an economic burden worldwide on agriculture, through yield reductions and cost of control. There is a prominent need for the development and implementation of sustainable control mechanisms, to reduce the widespread use of hazardous nematicides. The incorporation of less hazardous nematicides has been suggested as a possible step to move towards this. This study aimed to address commercially relevant and ecological important questions on the use of a potential novel nematode control agent, BGT, as developed by Arcis Biotechnology Ltd. In laboratory assays, bacterial species and a yeast showed different levels of susceptibility to BGT exposure. It is difficult to extrapolate the concentrations used to that at which the product would be in the soil but these studies suggest that soil application would likely cause changes in the microbial community structure. Soil samples were taken from experimental plots on a UK potato field following treatment applications to explore both immediate impacts and recovery of microbial communities. The changes in functional bacterial diversity and metabolic potential were estimated using community-level physiological profiling (CLPP). Additionally, taxon-specific quantitative PCR was used to detect changes in the bacterial and fungal community structure. The BGT treatments resulted in changes in the diversity of substrate utilisation as recorded by CLPP. Differences in utilisation patterns indicate repeated BGT treatments of 4 L/ha are likely to change the bacterial community structure. The use of qPCR showed that BGT treatments at 8 L/ha led to changes in the relative abundance of bacterial and fungal taxon groups. Although no significant changes in total abundance of bacterial communities were detected and current theory suggests that a small loss of diversity may not have a major impact on current soil functioning, it may impair long term soil health and ultimately productivity. In controlled toxicity assays, BGT was found to be of relatively low toxicity to earthworms, suggesting it is of low risk to terrestrial organisms. When applied directly to seed of wheat and tomato, BGT caused some reduction in seedling growth but treatments did not appear to cause any phytotoxic effects on wheat plants in glasshouse trials or on potato crops in field trials following both pre-planting and repeated application during plant growth.