Mehdi Trad

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.

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.

Relationship between pollination and cell wall properties in common fig fruit.

Most botanical types in fig Ficus carica require pollination to fulfil their development and ensure quality onset of the fruit. Cell wall behaviour and composition was followed in fig fruit in response to pollination during maturity. Figs, when ripe, soften drastically and lose of their firmness and cell wall cohesion. Pollination increased peel thickness, flesh thickness, fresh weight and dry matter content of the fruit. Alcohol insoluble solids (AIS), more concentrated in the flesh tissue, were not influenced by the lack of pollination. Concentrations in uronic acids were higher in the AIS of the peel than that of the flesh and differences were significant between pollinated and non-pollinated fruits. Pectin polymers in figs were high methylated (DM>50). The methylation degree (DM) increased more with pollination affecting textural properties of the fig receptacle. The major neutral sugars from the AIS were glucose (Glc) from cellulose followed by arabinose (Ara). No significant changes in neutral sugars content could be allocated to pollination. Pollination is essential in fruit enlargement and softening. Minor changes were determined in the cell wall composition of the fruit at maturity. Fertile seeds resulting from pollination may possibly take place in hormonal activity stimulating many related enzymes of the wall matrix depolymerisation in particular polygalacturonase (PG) and pectin methylesterase (PME).

Shoot Architecture and Morphology of Different Branch Orders in Fig Tree (Ficus carica L.)

ABSTRACT Tree architecture describes plant form by defining the spatial organization of different structures. Shoot branching is an important step in understanding the tree architecture. Such studies are required for analyzing phenotypic diversity of plant architecture. Because such studies are rare on fig trees, the architecture diversity among nine Tunisian fig cultivars grown in Chott-Mariem (center-east Tunisia) was explored. Quantitative morphological descriptors were noted on six annual shoots and studied during four yearly growth cycles, from 2007–10. Coding strategy was adopted for fig branch description. Branch growth characteristics, location, and distribution of axillary shoots were determined for three axis orders. Results showed a great variability of fig branches, particularly in terms of branching density and position, branching angle, and shoot dimensions. Shoot length was closely related to its architectural position in the branch, i.e., all low-order shoots in all cultivars had more growth than high-order shoots. The meso-basitony tendency was frequent. Thus, an architectural typology characterizing all cultivars was established and three principal groups were distinguished. The first one (Type I) with orthotropic branches located at the basal and median parts of the bearer axis had dense and continuous ramification. The second group (Type II) with a diffuse branching differed in lateral shoot distribution, and finally, the third group (Type III) had open and diffuse branching located on the basal zone of the carrier axis. This typology could be used in future genetic improvement programs of local fig trees in Tunisia.

Assessment of Seed Propagation Ability of Almond Genotypes ( Prunus dulcis (Mill.) D.A. Webb.) for a Mediterranean Environment

Several almond genotypes adapted to different climates of Tunisia have been identified and maintained in order to valorize their progenies as seedling rootstocks. This study aims to assess nut morphological characteristics and seed propagation ability of twelve local, two foreign and six hybrid almond genotypes having a very broad range of flowering period. Significant differences were observed among these genotypes. Seed germination started between 25 and 75 days from stratification date, was important for the majority of the genotypes and seems not affected either by the porosity or the hardness of the shell. The highest mean diameter of the radicle was recorded for G14-7, G25-5 and G23-15 genotypes. The emergence of seedlings was important in nursery.

The Glucose-Fructose ratio of wild Tunisian grapes

Abstract Glucose and fructose make up the bulk of sugars in grapes at all stages of development of the berry. The present study was made to determine the glucose/fructose balance of 17 wild grapes Vitis vinifera subsps. sylvestris growing under Mediterranean conditions of Tunisia for future breeding programs and selection. Cultivar “Meski Rafraf” (MKR) was used as reference for evaluation of wild ecotypes. Grape samples were collected from the North-west of Tunisia during 2014 and 2015. Glucose and fructose were the main sugars described in wild berries. Sucrose was present in little amount (<0.1 g/100 g FW). Except for ecotype 33 (EC.33), glucose was higher than fructose in all accessions. EC.46 is high-glucose ecotype (9.69 g/100 g FW) and would yield less sweet and better-balanced musts. EC.10 and EC.13 are high-fructose ecotypes (6.49 and 6.45 g/100 g FW respectively) and would result in sweeter tasting musts at lower total sugar content. The glucose/fructose ratio of wild Tunisian grapes varied over a wide range, from at least 0.26 (EC.33) to 12.38 (Cap Negro 6/2000) with differences being highly significant (p < 0.01). Grapes from cultivar “Meski Rafraf” showed an average value of 1.22. This cultivar belongs to the same homogeneous subset composed by EC.01, EC.10, EC.13, EC.15, EC.26 and EC.33. The level of reducing sugars in grape berry should represent an ideal tool for harvest date prediction and for sensory evaluation of wild grapevines. This study will help to lay out the foundation for accelerating the progress of trait improvement of quality in local grapevine resources.