Carotenoids and colour diversity of traditional and emerging Tunisian orange cultivars (Citrus sinensis (L.) Osbeck)

Citrus are among the most cultivated fruit crops worldwide and occupy a paramount importance in the Tunisian agricultural sector being one of the strategic products. Despite of that, little is known about the quality parameters of Tunisian sweet oranges and some cultivars have not been characterized yet. This work aims to study the coloration diversity of twenty-five Tunisian grown oranges by analyzing their total and individual carotenoids content and the relationship with CIELab color coordinates. Experimental results proved large diversity in the carotenoid composition of the studied juices. Maltaise demi-sanguine cultivar was distinguished from the rest due to its high content of ζ-carotene, lutein and total carotenoids. An unusual lycopene accumulation was detected in the juice of Meski Ahmer. The Tunisian grown Washington Navel cultivar ranked within the rich-carotenoids juices. In addition, significant negative correlations were found between lightness parameters (L*) and Hue angle (H) while they were positively related with redness attributes (a*). Furthermore, (all-E)-violaxanthin and ζ-carotene were both significantly correlated to yellow color intensity index (b*) while zeaxanthin and lutein were positively related to Chroma (C*) and (b*) indices. These findings are of interest since the carotenoids content and composition are directly related to color and citrus juice quality. The results obtained could be part in a selection program-guide of Tunisian cultivars and help to understand the physiological and biochemical bases of sweet orange coloration.This work was supported by the Tunisian Ministry of Higher Education and Scientific Research [Alternance scholarship, April-Juin 2015] and by research grants from Ministerio de Economía y Competitividad, Spain. Financial support from PROMETEO 2014/0027 (Generalitat Valenciana, Spain) is also acknowledged. M-J.R. and L.Z are members of the CaRed network (BIO2015-71703-REDT), and S.B.A., M-J.R. and L.Z are members of the EUROCAROTEN COST Action (CA15136).Peer reviewe

Recovery, Assessment, and Molecular Characterization of Minor Olive Genotypes in Tunisia

Olive is one of the oldest cultivated species in the Mediterranean Basin, including Tunisia, where it has a wide diversity, with more than 200 cultivars, of both wild and feral forms. Many minor cultivars are still present in marginal areas of Tunisia, where they are maintained by farmers in small local groves, but they are poorly characterized and evaluated. In order to recover this neglected germplasm, surveys were conducted in different areas, and 31 genotypes were collected, molecularly characterized with 12 nuclear microsatellite (simple sequence repeat (SSR)) markers, and compared with 26 reference cultivars present in the Tunisian National Olive collection. The analysis revealed an overall high genetic diversity of this olive’s germplasm, but also discovered the presence of synonymies and homonymies among the commercialized varieties. The structure analysis showed the presence of different gene pools in the analyzed germplasm. In particular, the marginal germplasm from Ras Jbal and Azmour is characterized by gene pools not present in commercial (Nurseries) varieties, pointing out the very narrow genetic base of the commercialized olive material in Tunisia, and the need to broaden it to avoid the risk of genetic erosion of this species in this country