Characterising Impacts and Responses to Single and Combined Abiotic Stress Exposure in the Legume Species Lotus japonicus and Vigna unguiculata

Abstract

Abiotic stress poses a threat to food security through adverse effects on crop health and function, resulting in reduced yield or crop failure. Plants possess a myriad of physiological and biochemical properties by which abiotic stress
protection can be conferred, varying between species and to genotype level. Better characterising these responses for individual species will aid in the development of more abiotic stress tolerant crops. Identification of geographic regions of interest for tolerance traits could allow for targeted sampling in breeding and development programmes. Landrace accessions of cowpea (Vigna unguiculata) and the model legume Lotus japonicus var. gifu were assessed at seedling stage for their response to drought, heat, and waterlogging stress, plus combinations of these. In L.japonicus the interaction between root nodulation with rhizobia was also investigated. Physiological assessment examining photosynthetic performance, gas exchange, and water loss were used alongside metabolomic profiling to provide a holistic overview of plant response to stress. Variation in biological function in cowpea appeared to be driven to greater extent by water deficit, whereas high temperature caused greatest significant variation in L. japonicus. In both species, metabolites associated with amino acid and carbon metabolism were significantly enriched indicative of impacts on plant primary metabolism. The combination of heat and drought demonstrated exacerbated effects in comparison to single stress. Nodulated L.japonicus plants showed limited nitrogen assimilation compared to ammonium nitrate supplied plants, however they also demonstrated less metabolite fluctuation under abiotic stress indicting potential biotic influence. Ecological niche modelling indicated potential association between environmental background and metabolic behaviour. It was concluded that further work characterising metabolic pathways associated with tolerance traits be undertaken at multiple growth stages to demonstrate impacts on end yield. Combining this data with ecological niche modelling processes has the potential to further illustrate the relationship between environmental background and tolerance.

Date of Award	2019
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Luis Mur (Supervisor) & Hefin Williams (Supervisor)