Carotenoid profiling of the leaves of selected African eggplant accessions subjected to drought stress

Abstract

African eggplants (Solanum aethiopicum and S. macrocarpon) are among the most economically important and valuable vegetable and fruit crops. They are a major source of biologically active nutritional substances and metabolites which are essential for plant growth, development, stress adaptation and defense. Among these metabolites are the carotenoids which act as accessory pigments for photosynthesis and precursor to plant hormones. Though African eggplants are known to be resistant to various abiotic stresses, the effect of these stresses on secondary metabolites has not been well defined. The objective of this study was to establish the effect of drought stress on carotenoid profiles of nineteen African eggplant accessions selected based on leaf and fruit morphological traits. Stress was achieved by limiting irrigation and maintaining the wilting state of the crops. Fresh leaves were sampled at different maturity stages; before stress, 2 weeks and 4 weeks after stress for carotenoid analysis. The fresh harvested leaf tissues were immediately frozen in liquid nitrogen and ground. Analysis was carried out using a Dionex HPLC machine coupled to Photo Array Detector and Chromeleon software package (Thermo Fisher Scientific Inc, Waltham, Massachusetts, USA). Major carotenoids viz;. Xanthophylls (neoxanthin, violaxanthin, zeaxanthin and lutein) and carotenes (β–carotene and α–carotene), phytofluene, lycopene, phytoene as well as chlorophylls (chlorophyll‐b and Chlorophyll‐a) were targeted. The carotenoids increased with maturity stage of the crop. Although the stressed crops reported significantly decreased amount of carotenes, chlorophylls, neoxanthin and violaxanthin, the concentration of zeaxanthin increased with stress whereas lutein had no significant change. Chlorophyll‐a was significantly high in all the control accessions. Two accessions reported significantly higher contents of carotenoids as compared to the other accessions. The results of this study indicate that water stress has significant impact on the concentration of some carotenoids and photosynthetic pigments. This will definitely add value to the study of stress tolerance in crops.

Physiological and Biochemical Responses in Onion Crop to Drought Stress

“…In potato, leaf chlorophyll content was used as an efficient indicator of tuber yield under drought condition (Ramirez et al, 2014). Recent findings in some vegetable crops like eggplant (Mibei et al, 2017) and raddish (Akram et al, 2016) further supports our finding where drought stress reduces the chlorophyll content however the tolerant cultivar maintains the higher chlorophyll and thereby the photosynthesis rate as one of the drought tolerance mechanism. Drought stress induces the formation of detrimental reactive oxygen species (ROS) that directly damages the cellular membrane that affects the various cellular metabolic processes (Das and Roychoudhury, 2014).…”

Impacts of warming and water deficit on antioxidant responses in Panicum maximum Jacq

“…According to Czarnocka and Karpiński (), plants subjected to abiotic stress form the triplet chlorophyll ( 3 Cl • ), which transmits excess energy to O 2 thereby forming ROS; however, this excess energy can be captured by carotenoids to avoid ROS formation. This behaviour of carotenoids, as a protective agent against water deficit, is reported by Mibei et al (), whereas Carvalho et al () observe an increase in carotenoid content in Vitis vinifera subjected to combined stresses (water stress + temperature increase).…”

Comparative metabolomics analysis reveals different metabolic responses to drought in tolerant and susceptible poplar species

“…This result was in line with previous studies, reporting the inhibition of TCA‐cycle by drought stress in Zea mays (Barnaby et al ), Caragana korshinskii (Zhang et al ) and Populus balsamifera (Hamanishi et al ). Contrasting data in Solanum aethiopicum showed that the TCA‐cycle's intermediates increased under drought stress to enhance the energy production (Mibei et al ). Furthermore, varied patterns of accumulation have been found in different genotypes of same plant species, indicating different defense strategies (Yang et al ).…”

“…In A. thaliana , α‐tocopherol can move easily within lipid membranes because of its adequate fluidity, and it eliminates ROS free radicals to prevent lipid peroxidation (Kim et al , ). The carotenoids, β‐carotene and zeaxanthin, are not only essential for photosynthesis and photoprotection, but they are also precursors to phytohormones, such as ABA and strigolactone, which are potent antioxidants and free radical scavengers (Cazzonelli , Mibei et al ). Oxidative stress leads to lipid peroxidation, protein denaturation, DNA mutations, and various types of cellular oxidative damage (Smirnoff ).…”