Elucidating the responses of chickpea to drought stress and soils differing in nematode, microbiome, and nutrient composition via untargeted metabolomics

Chickpea is a major food legume which is exposed to abiotic and biotic stresses inducing yield-loss worldwide. Canada is an important exporter of chickpea; most of the production comes from Saskatchewan, which is frequently exposed to drought. Recently, high levels of ectoparasite nematodes have been detected in some commercial chickpea fields in Saskatchewan. This study explored the mechanisms of chickpea responses to drought and soils differing in nematode densities, microbiome, and nutrients, using an untargeted metabolomics approach. Multivariate and univariate analyses showed clear separation of metabolites between drought and well-watered treatments in both leaves and roots of chickpea, while the soil resulted in less distinct separation. A three-tier approach positively or putatively identified 18422 and 17838 peak pairs, or metabolites, in leaves and roots, respectively. In leaves, proportions of metabolites in tier 1 and tier 2 were 3.1 and 14.1%, respectively, while were 3.4 and 14.5% in roots. There were substantial changes in phytohormones, phenylpropanoids, flavonoids, amino acids, fatty acids, alkaloids, and vitamins in response to drought. Soil was linked to changes in metabolites of the same classes, except fatty acids. However, far fewer individual metabolites changed in association with soil than drought. The results of this study will improve our understanding of chickpea responses to environmental stresses, that might be useful in developing climate resilient crop production systems.