Exploiting the growth promotion and induced resistance properties of Trichoderma hamatum for improved crop productivity.

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With the human population projected to reach 9 billion by the year 2050, unsustainable demands will be placed on global agriculture to meet future food requirements. Improvements in crops yields that have traditionally relied on plant breeding and energy intensive agriculture are unlikely to meet these needs and therefore marginal land, previously considered unsuitable for agriculture, will need to be brought into cultivation. Much of this land will have sub-optimal fertility and nutrient-poor soils requiring substantial inputs of synthetic fertilizers to support sustainable crop production. However, significant increases in the price of fertilizers mean many farmers, particularly in developing countries, cannot afford such management practises. The spiraling financial burden of fertilizers, combined with growing public anxiety of the environmental and health impacts of synthetic chemical additives, means that alternative strategies for sustainable crop production need to be examined urgently. Trichoderma strains produce a diverse array of secondary metabolites and secreted proteins. Trichoderma isolates have been shown to activate broad spectrum immunity, ameliorate a wide range of abiotic stresses such as salinity and drought, improve photosynthetic efficiency, enhance nutrient uptake, and significantly increase nitrogen use efficiency in crops. These important attributes can all contribute to the enhanced plant growth characteristics often evident upon inoculation. The positive agronomic traits of growth promotion, enhanced tolerance to abiotic stress and broad spectrum enhanced systemic immunity afforded by many Trichoderma strains are striking and unique. The ability to exploit the signaling networks activated by Trichoderma to establish these agriculturally beneficial traits requires an understanding of both the bioactive inducing molecules and the signaling networks targeted by these activators. The rapid developments in genomic and analytical technologies means this is an opportune time to exploit the amazing chemical diversity of soil micro-organisms such as Trichoderma, with the objective of improving PGP and ISR on a range of agronomically important plant species. Research conducted at Exeter has identified a novel strain of the naturally occurring rhizosphere fungus Trichoderma hamatum (strain GD12) that improves crop productivity and imparts broad spectrum enhanced immunity to pathogens in the absence of costly fertilizers and environmentally damaging agrochemicals. At present, the mechanism underlying the plant-growth-promotion and enhanced systemic resistance phenomena are unknown and this proposal lays the foundations to address the molecular basis of the inducing bioactives and the plant response pathways targeted by these bioactives. This combined knowledge is important, and necessary to contemplate translating Trichoderma PGP and ISR into the agricultural arena. This multidisciplinary research programme will use a combination of genetics, genomics and metabolomics to unravel Trichoderma PGP/ISR bioactives, capture the plant transcriptional reprogramming induced by the bioactives and identify key components of the PGP, ISR signaling networks. We will use comparative transcriptomics to characterize signaling pathways in Arabidopsis and rice activated by Trichoderma inoculation. In combination with mutant Trichoderma and Arabidopsis lines compromised in phytohormone signaling we will identify candidate signaling components/pathways that contribute to PGP and ISR. We will undertake comparative metabolic profiling using liquid chromatography mass spectrometry to characterize the bioactives and test their efficacy on different plants with the objective of developing novel natural agrochemicals.