title: Carotenoid profiling of the leaves of selected African eggplant accessions subjected to drought stress.
abstract: African eggplants (Solanum aethiopicumandS.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 andα-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.
authors.affiliation: Department of Food Science and Technology Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya.
authors.forename: Elias K
authors.initials: EK
authors.lastname: Mibei
authors.affiliation: Department of Plant Science and Crop Protection University of Nairobi Nairobi Kenya.
authors.forename: Jane
authors.initials: J
authors.lastname: Ambuko
authors.affiliation: Boyce Thompson Institute for Plant Research Cornell University Campus Ithaca New York 14853.
authors.forename: James J
authors.initials: JJ
authors.lastname: Giovannoni
authors.affiliation: Department of Food Science and Technology Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya.
authors.forename: Arnold N
authors.initials: AN
authors.lastname: Onyango
authors.affiliation: Department of Food Science and Technology Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya.
authors.forename: Willis O
authors.initials: WO
authors.lastname: Owino
keywords: African eggplants; Carotenoids; chlorophylls; drought stress; stress tolerance