Messaoud Mars

Comparative Assessment of SSR and AFLP Markers for Evaluation of Genetic Diversity and Conservation of Fig, Ficus carica L., Genetic Resources in Tunisia

This study characterises the genetic variability of fig, Ficus carica L., using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. It compares the efficiency and utility of the two techniques in detecting variation and establishing genetic relationships among Tunisian fig cultivars. Our results show that using both marker systems, the Tunisian fig germ plasm is characterised by having a large genetic diversity at the deoxyribonucleic acid level, as most of AFLP bands were detected and all SSR markers were polymorphic. In fact, 351 (342 polymorphic) and 57 (57 polymorphic) bands were detected using AFLP and SSR primers, respectively. SSR markers were the most polymorphic with an average polymorphic information content value of 0.94, while AFLP markers showed the highest effective multiplex ratio (56.9) and marker index (45.2). The effective marker index was recorded highest (4.19) for AFLP markers and lowest (0.70) for the SSR ones. Our results demonstrate that (1) independent as well as combined analyses of cluster analyses of SSR and AFLP fragments showed that cultivars are clustered independently from their geographical origin, horticultural classifications and tree sex; (2) the analysis of molecular variance allowed the partitioning of genetic variation within and among fig groups and showed greater variation within groups and (3) AFLP and SSR markers datasets showed positive correlation. This study suggests the SSR and AFLP markers are suitable for diversity analysis and cultivars fingerprinting. An understanding of the genetic diversity and population structure of F. carica in Tunisia can also provide insight into the conservation and management of this species.

Molecular genetic diversity of Punica granatum L. (pomegranate) as revealed by microsatellite DNA markers (SSR)

Pomegranate (Punica granatum L.) is one of the oldest known edible fruits and more and more it arouse interest of scientific community given its numerous biological activities. However, information about its genetic resources and characterization using reliable molecular markers are still scarce. In the present study, we report the development of 4 new polymorphic SSR markers. They have been used in addition to 11 SSRs previously published to investigate molecular diversity of 33 P. granatum ecotypes. Based on the multi-locus profiles, twenty-two distinctive genotypes were identified. Globally, quite low genetic diversity has been revealed, as measured by allele richness (2.83 per locus) and heterozygosity (He=0.245; Ho=0.243), reflecting the narrow genetic background of the plant material. Four synonymous groups could be detected involving 15 accessions. Results of ordination and cluster analysis suggested that almost all the Tunisian cultivars share similar genetic background, and are likely derived from a small number of introductions in ancient times. Results issued from this study provide essential information to project a pomegranate core-collection without plant material duplication and for sustainable management of pomegranate landraces at national and international level. Furthermore, these SSR markers are powerful tool for marker assisted selection (MAS) program and for QTL studies.

Organic Acids, Sugars, and Anthocyanins Contents in Juices of Tunisian Pomegranate Fruits

Juices made from fruits of 30 Tunisian accessions of pomegranate were studied for their organic acids, sugars, and anthocyanin contents, using high performance liquid chromatography. Among the detected organic acids, malic acid was the major one (>50%) followed by citric acid (>22%), while among sugars, fructose and glucose were most present in pomegranate juice contributing 53.9 and 43.4% of the total sugar content, respectively. The total anthocyanin content ranged from 9–115 mg per litre of juice with the following ranges of the six compounds found: cyanidin-3,5-diglucoside (3.1–74.4 mg/L), delphinidin-3-glucoside (0.7–22.0 mg/L), cyanidin-3-glucoside (0.8–21.0 mg/L), pelargonidin-3-glucoside (0.5–16.1 mg/L), pelargonidin-3,5-diglucoside (0.0–11.8 mg/L), and delphinidin-3,5-diglucoside (0.0–5.4 mg/L). Based on the analyzed parameters, cluster analysis allowed grouping cultivars into two main clusters. One was made of sour cultivars and the second of the sweet ones. Principle component and cluster analyses suggested that the composition of the pomegranate fruits is determined by cultivar rather than cultivation location.

Morphological Variability of Fig (Ficus carica L.) Cultivars

ABSTRACT Thirty one cultivars of fig (Ficus carica L.) were analyzed based on both qualitative and quantitative morphological characters. The cultivars can be found in five different regions: three originated from the north and two from localities from the south of Tunisia. A morphological study was conducted to determine variables in biological characteristics, tree growth, and leaf and fruit descriptors. This study showed an important genetic variability on fig germplasm. Both parameters relying on leaves and fruits showed an important degree of variability respectively about 71.7% and 81.9% for the three first principal components. UPGMA dendrograms were constructed from estimated Mahalanobis distances. The geographic origin and sex of the plant were not determinant criteria for cultivars clustering. This study allowed the characterization of large number of fig cultivars belonging to different regions of Tunisia ranging from north to south. The aim of this work was the morphological characterization of local fig varieties in order to start a program of conservation of fig germplasm to protect this species from genetic erosion.

Development and characterization of SSR markers for pomegranate (Punica granatum L.) using an enriched library

In the present work, we report the development of 11 microstallite markers (SSR) for Punica granatum. Evaluated on a set of 27 pomegranate accessions sampled in Tunisia, they displayed 25 alleles, with number of alleles per locus ranging between 1 and 4, and an observed heterozygosity from 0.037 and 0.592. This set of SSR markers can be very useful for studies dealing with genetic diversity assessment of germplasm, with cultivars/varieties fingerprinting and pedigree analysis of this economically important fruit species.

Morphological and Pomological Diversity of Fig (Ficus carica L.) Cultivars in Northwest of Tunisia

The fig (Ficus carica L.) is one of the oldest fruit trees cultivated in Tunisia. Djebba region is located in the northwest of Tunisia. It is very famous by fig culture. Many specific fig genotypes are very appreciated locally and nationally. Taking into account these considerations, Djebba fig cultivars are subject of label products, namely, “Djebba figs.” This study was focused on fig germplasm characterization of 17 cultivars in Djebba region based on morphological and pomological traits. Results revealed a large variability within the local fig germplasms. The comprehensive analyses of all the data permitted to distinguish some particular genotypes as distinct cultivars, and groups of cultivars as polyclone varieties. It was possible to discriminate six distinct cultivars and two groups of multiclone varieties (Soltani and Thgagli) with different degrees of polymorphism. Hypotheses of homonymy and synonymy were suggested for some cultivars. The diversity is currently threatened by genetic erosion. Measure of conservation is necessary to be undertaken.

Assessment of Pollen Viability, Germination, and Tube Growth in Eight Tunisian Caprifig (Ficus carica L.) Cultivars

The evaluation of pollen viability and its germination capacity are two essential criteria for pollinator’s characterization. This study was carried out to evaluate pollen quality of eight caprifigs grown in the center-east and north-west of Tunisia. Two colorimetric tests 2,3,5-triphenyl tetrazolium chloride (TTC) and acetocarmine were used to estimate pollen viability. Germination rate and pollen tube growth in a culture medium containing 5% sucrose, 5 ppm boric acid (H3BO3) and 1% agar were registered after 24, 48, and 72 hours (H) of incubation. Results showed that the highest pollen viability rate (84%) was obtained by TTC test in caprifig Assafri, followed by Jrani (80.2%), Djebba 2 (77.8%), and Djebba 1 (73.6%). That of other caprifigs did not exceed 50% for the two tests. In all caprifig types, germination rate and pollen tube growth varied according to the incubation period. The highest percentage of germination (72%) and maximum pollen tube length (960 μm) were recorded after 72 H of incubation in caprifigs Assafri and Jrani, respectively. Among the caprifigs studied, four types (Assafri, Jrani, Djebba 1, and Djebba 2) appeared to be suitable pollinators with respect to the criteria investigated.

Development of molecular tools for characterization and genetic diversity analysis in Tunisian fig (Ficus carica) cultivars.

Fig, Ficus carica L., is a useful genetic resource for commercial cultivation. In this study, RAPD (60), ISSR (48), RAMPO (63), and SSR (34) markers were compared to detect polymorphism and to establish genetic relationships among Tunisian fig tree cultivars. The statistical procedures conducted on the combined data show considerable genetic diversity, and the tested markers discriminated all fig genotypes studied. The identification key established on the basis of SSR permitted the unambiguous discrimination of cultivars and confirmed the reliability of SSR for fingerprinting fig genotypes. The study findings are discussed in relation to the establishment of a national reference collection that will aid in the conservation of Tunisian fig resources.

Diversity Among Tunisian Pomegranate (Punica granatum) Cultivars as Assessed by Pomological and Chemical Traits

Twenty-one local pomegranate cultivars maintained in an ex-situ collection in Tunisia, were studied using 29 characteristics related to flowers, fruits, and seeds. Results showed an important phenotypic diversity. Some accessions were considered as particular cultivars (Garsi1, Zehri11, Tounsi2, and Jerbi1). Some others (Gabsi, Chelfi) were considered as multiclone varieties. Synonyms and homonyms could be detected among cultivars. These results emphasize the importance of morphological descriptors to identify pomegranate varieties and allowed to recommend cultivars for different uses (table fruit, juice, and derivatives). Nevertheless, these descriptors need to be completed by further studies as biochemical and molecular characterization.

Nutritional Compounds in Figs from the Southern Mediterranean Region

Nutritive value of mature figs (Ficus carica L.) was investigated in five Tunisian cultivars, ‘Bouhouli’ (BHL) and ‘Zidi’ (ZD) (dark skin figs); ‘Thgagli’ (THG), ‘Bidhi’ (BD), and ‘Khedri’ (KHD) (yellow-green skin figs). Sugars, organic acids, fibres, and polyphenols were analysed in representative fruit samples from two distinct regions known to develop fig crops. Tunisian figs were characterized by predominance of glucose (6.30 g/100 g fresh weight) and fructose (5.10 g/100 g fresh weight). Citric acid (0.35 g/100 g fresh weight) was the major organic acid in all cultivars, almost three times higher than malic acid (0.13 g/100 g fresh weight). Average content of alcohol insoluble solids was 3.3 g/100 g FW. Four main polyphenols could be identified: two anthocyanins (cyanidin-3-glucoside; cyanidin-3-rutinoside), one flavonol (rutin), and one hydroxycinnamic acid (5-cafeoylquinic acid), revealed only in ‘BD’ samples. Cyanidin-3-rutinoside was the most abundant compound among all cultivars. Compared to common fruit, figs are among high sugar leveled fruit with significant dietary fibre content. Dark skin ‘ZD’ fruit were the most interesting figs with the highest concentration of sugars, organic acids, and polyphenols, especially cyanidin-3-rutinoside. This cultivar could be better advised for fresh consumption. However, the three lighter cultivars are more suitable for drying.