Role of proline accumulation on fruit quality of pepper (Capsicum annuum L.) grown with a K-rich compost under drought conditions

Abstract

Water availability is the most critical factor to growth and development of plants, which limits the productive potential of plants. Plants adapt to water deficits by physiological alterations, biochemical changes and osmotic adjustments. The aim of this study was to investigate the effect of soil amendment of a K-rich carrot compost on pepper (Capsicum annuum L. cv. Paco) physiology and fruit quality under drought. Furthermore, an attempted to determine the influence of these combined factors on yield and quality pepper fruits. Carrot compost (ZC) was obtained by aerobic composting from carrot wastes from packing plants and not presented phytotoxic substances that prevented germination and grown of pepper seedlings. When the vegetative stage corresponding to start of flowering was reached, half of the plants were subjected to drought conditions (moderate water stress). Results showed that the concentration of minerals, free proline, total phenols and main carotenoids (β-carotene and lycopene) in pepper fruits were significantly modified by water level and/or substrate type. Under drought, plants grown in a mixture of 35% ZC and 65% soil (ZC35) increased concentrations of minerals (mainly K) and phenols but decreased β-carotene and lycopene levels. Moreover, significant relationships between K content, phenolic compounds and free proline were highlighted. Overall, data suggest that the use of a K-rich carrot compost for growing pepper under drought could selectively modify plant metabolic activities that are involved in the accumulation of carotenoids and phenolic compounds and thus, in fruit quality.