Growth and antioxidant responses triggered by water stress in wild relatives of eggplant

Abstract

Wild relatives of eggplant (Solanum melongena) are of interest for breeding for tolerance to drought. To assess the potential of eggplant wild relatives from different gene pools, 18 accessions belonging to eggplant and eight wild relatives were evaluated for water stress tolerance. Plants grown in pots were normally irrigated or subjected to water stress by stopping irrigation. Growth and biochemical parameters related to oxidative stress, including proline, malondialdehyde (MDA), total phenolics and total flavonoids contents, and catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities, were determined after 11 days of treatment. The reduction of dry matter content in the aerial part of the water-stressed vs. control plants allowed classifying the accessions into three groups: tolerant (< 25% reduction), intermediate (25–35% reduction), or susceptible (> 35% reduction). Proline concentration increased in all accessions under water stress, in particular in the more tolerant ones, which showed an average increase of more than 30-fold over control values, compared to ca. 8-fold in the susceptible accessions. The group of tolerant accessions, which included S. incanum, S. pyracanthos, S. dasyphyllum and S. torvum, was also characterised by unchanged MDA contents and a more pronounced increase in the mean levels of flavonoids (20.6% over the non-stressed controls vs. 3.4% in the intermediate accessions and 5.0% in the least tolerant ones). The activity of antioxidant enzymes was extremely variable within groups and even within the same species. The results obtained reveal a high diversity for drought tolerance in the wild relatives of eggplant and provide insights into the biochemical mechanisms involved in the response to drought in eggplant wild relatives. The tolerant materials identified are of interest for breeding programmes for developing rootstocks and new eggplant cultivars with higher drought tolerance.