Drought response of cowpea (Vigna unguiculata (L.) Walp.) landraces at leaf physiological and metabolite profile levels

Abstract

Drought threatens the world's food production, particularly in Sub Saharan Africa low external input and rain fed agricultural systems, where cowpea (Vigna unguiculata (L.) Walp.) is an important food crop. In the context of growing concerns regarding climate changes implications on water availability, this study aimed at 1) to evaluate the drought responses in cowpea landraces with contrasting drought tolerance levels (A55high sensitivity; A80 -mild sensitivity; A116 -tolerant), 2) using an integrated physiological (leaf gas exchanges; chlorophyll a fluorescence) and biochemical (photoprotective pigments; RuBisCO activity; primary metabolite profiling) analysis to identify drought tolerance probes, in plants submitted to three water availability levels (well-watered, WW; mild drought, MD; severe drought, SD). A116 plants maintained a better water status under drought, what could justify the higher P n and P nmax values in MD, as well as higher photochemical use of energy (reflected in the photochemical quenching (q L ) and in the quantum yield of non-cyclic electron transport (Y (II) )), and the lower need of photoprotective thermal dissipation mechanisms (given by the non-photochemical quenching (q N ), and the quantum yield of regulated energy dissipation at photosystem PSII (Y (NPQ) )), in MD and SD plants. Greater declines of net (P n ) and potential (P nmax ) photosynthesis were observed in A55 plants, which frequently showed significant impacts already under MD conditions in most parameters, whereas A80 usually displayed and intermediate behaviour. Still, even A55 showed some acclimation response, regarding photoprotective mechanisms associated with high contents of zeaxanthin, lutein, and carotenes, and high Y (NPQ) , and q N values, supporting the absence of an increase in the non-regulated energy dissipation at PSII (Y (NO) did not increased) even in SD plants. Additionally, A55 was not significantly affected in RuBisCO activity, which showed to be quite resilient in cowpea. A primary metabolite profiling, complemented with a partial least square discrimination analysis (PLS-DA), allowed a better separation of A116 and A55 plants according to their degree of drought tolerance. In response to drought, A116 showed the greatest accumulation of most responsive metabolites, 14 in total, with sucrose, fucose, urea, alanine and putrescine being exclusively increased in this genotype, suggesting that they can be candidates as drought tolerance proxies. Other compounds, as proline, valine, isoleucine (among amino acids), and rhamnose and raffinose (among sugars) showed close increase patterns

Exploring physicochemical and cytogenomic diversity of African cowpea and common bean

“…Three species are classified as Data Deficient and 25 remain unevaluated, revealing the lack of knowledge about them. The evaluation of the conservation status, as well as the study of their threats, distribution and ecology, based upon extensive fieldwork, is a required step to protect native species 16 , 44 , 45 . Of particular concern are V. monantha , V. bosseri and V. keraudreni , which are classified as endangered and are not preserved in gene banks.…”

Genetic Diversity among Cowpea (Vigna unguiculata (L.) Walp.) Landraces Suggests Central Mozambique as an Important Hotspot of Variation

“…Population structure analysis using worldwide cowpea samples usually delineates African landraces into two major gene pools separated by the Congo River basin, the East/South, and West Africa [8][9][10], although nothing has been reported in terms of the cowpea genetic structure within these regions. Our study, focused on Mozambican (East Africa) landraces, found four genetic groups with a high degree of admixture ( Figure 5).…”

Metabolite Analysis of Jerusalem Artichoke (Helianthus tuberosus L.) Seedlings in Response to Polyethylene Glycol-Simulated Drought Stress

“…Pan et al [ 25 ] found the differential expression of lipids, amino acids, organic acids, carbohydrates, and carbohydrate conjugates; nucleotides and their analogs; indoles and their derivatives; alkaloids and their derivatives; amine compounds, pyridines, and their derivatives in the metabolic processes of two annual ryegrass under drought stress. Gomes et al [ 26 ] discovered that a total of 14 metabolites increased exclusively in cowpea, including sucrose, fucose, urea, alanine, and putrescine. Metabolomics are an effective method to explain plant growth and adaptation mechanisms in harsh environments [ 27 , 28 ], and has been widely used to investigate plant response to abiotic stresses.…”