Improvement of Salt Tolerance Potential of Solanum melongena through Backcrosses with Solanum linnaeanum

Abstract

Soil salinity is a major constraint on global agriculture, severely limiting the crop productivity. Eggplant (Solanum melongena L.), an economically important vegetable, is particularly sensitive to salt stress. Wild relatives such as Solanum linneanum L. provide valuable genetic resources for improving stress tolerance. This study evaluated the salt tolerance potential of S. linneanum and its backcross progenies with cultivated eggplant, aiming to identify breeding materials for the development of resilient cultivars. Three backcross lines (Lin1, Lin2, Lin3), derived from S. linneanum and the open-pollinated cultivar ‘Topan374’, were tested alongside ‘Topan374’ (negative control) and S. linneanum (positive control). The experiment followed a completely randomized block design with three replications, each consisting of six plants. Plants were subjected to 150 mM NaCl, and tolerance levels were assessed through morphological parameters (plant height, stem diameter, leaf number, anthocyanin presence and prickliness) and physiological stress indicators, including malondialdehyde (MDA) and proline content. Salt stress significantly reduced growth traits across genotypes. The wild parent maintained superior tolerance under 150 mM NaCl stress, while the backcross progenies (Lin1, Lin2, Lin3) showed better morphological performance than the sensitive cultivar, retaining higher growth under salinity. In addition, they exhibited elevated MDA and proline levels, in some cases exceeding those of the positive control, indicating activation of protective stress mechanisms. These findings demonstrate that introgression from S. linneanum can enhance salt tolerance in cultivated eggplant. The promising performance of backcross lines highlights their potential as valuable genetic resources for breeding salt-resilient cultivars, supporting sustainable eggplant production in saline-prone environments.