**1. Introduction**

Eggplant (*Solanum melongena* L.) is the world's sixth most important vegetable after tomato, watermelon, onion, cabbage, and cucumber [1] and the most important *Solanum* crop native to the Old World [2]. Sicily is one of the most important production areas within the Mediterranean Basin that is considered a secondary center of diversification [3]. Soilborne diseases arising from continuous cropping are major problems that limit productivity in eggplant [4]. Therefore, improving soilborne resistance is one of the major scientific and economic challenges in eggplant. Grafting has been attempted as an effective mean to control soilborne diseases and abiotic stresses while simultaneously not adversely affect plant growth or even to improve vigor and yield [4]. Among the abiotic stresses

that affect vegetable crops, salinity continues to be a main factor in reducing vegetable crop yield and profits in many arid and semi-arid regions. In this respect, Colla et al. [5] demonstrated the effectiveness of grafting to improve salinity tolerance in cucumber. However, the use of specific rootstocks may offer many other advantages such as drought resistance [6] or heavy metal tolerance [7].

*Solanum torvum* Sw. is the rootstock commonly used for grafting, especially in the most intensive protected cultivation. However, its use has been limited due to lack of rapid and homogeneous synchronized seed germination [8]. Studies have shown that grafting can affect yield and fruit quality in eggplant [9,10]. Kyriacou et al. [11], in their review, reassessed that grafting itself and the prevalence of particular type of commercial rootstocks influence vegetable fruit quality and, partially, storability. They also reported that grafting significantly affects morphometric traits, textural characteristics, sweetness and acidity, as well as functional compounds in eggplant. However, according to Kyriacou et al. [11], current reports on the changes conferred by grafting on eggplant fruit quality provide conflicting information probably due to the environment in which experiment were run. In particular, they stressed both possible rootstock–scion interactions, underscoring graft combinations and different stemming from failure to standardize fruit harvest maturity. In this respect, Gisbert et al. [9] and Sabatino et al. [10] found that the use of interspecific hybrid rootstocks derived from compatible crosses of eggplant with related species can be a valuable approach to improve/preserve eggplant production.

*Solanum aethiopicum* gr. *gilo* (scarlet eggplant), a close relative species of *S. melongena*, has been considered a noticeable resource for eggplant genetic improvement and as potential rootstock. It presents traits of interest, including resistance to *F. oxysporum* f. sp. *melongenae*, *R. solanacearum* [12,13], and root-knot nematodes [14]. Since scarlet eggplant is a cultivated species, it does not display those undesirable traits that are commonly present in the wild relatives of eggplant such as small fruit production, presence of prickles, and high saponins and glycoalcaloids concentrations [15]. A great genetic and morphological variability has been evidenced in *S. aethiopicum* [16]; therefore, it is particularly relevant to characterize the accessions for the presence and expressivity of the traits of interest before starting a breeding program. Interspecific sexual and somatic hybrids between *S. melongena* and *S. aethiopicum* gr. *gilo* have been produced and although they present a high degree of sterility, recombination between the two genomes has been demonstrated [17] and backcross generations to *S. melongena* with useful introgressions of *S. aethiopicum* gr. *gilo* obtained [13,18,19]. The aim of this work was to explore the possibility to use two accessions of *S. aethiopicum* gr. *gilo* and an initial highly fertile introgression line (BC1) from the somatic hybrid between *S. melongena* and *S. aethiopicum* gr. *gilo* as rootstock for eggplant. The introgression line was resistant to *Fusarium oxysporum* f.sp. *melongenae* and is the founder of the series of improved eggplant lines resistant to *Fusarium* wilt carrying the resistant locus *RfoSa1* [18]. The effects of these three genetic materials when used as rootstock, on vigor, yield, and fruit quality traits of eggplant Scarlatti F1 hybrid were evaluated. The results are compared with those obtained from ungrafted, self-grafted, and *S. torvum* rootstock grafted plants. Therefore, our aim was also to validate the assumption that using interspecific hybrid rootstocks may be a good approach to enhance eggplant performance because the presence of the eggplant genome together that one of the wild/allied species may improve the overall affinity between rootstock and scion exploiting the advantage of grafting.
