Variability salt stress response analysis of Tunisian natural populations of Medicago truncatula (Fabaceae) using salt response index (SRI) ratio

We evaluated the responses to salt stress of 106 Medicago truncatula lines from 11 Tunisian natural populations collected from areas that varied in soil composition, salinity and water availability. Five references lines were also included in this study. Plants were cultivated in two treatments (0 and 50 mM of NaCl) during a period of 60 days. At harvest, we measured 14 quantitative traits of the aerial and root growth to identify genotypic variability in salt response. Analysis of variance showed that, the response to salt lines within populations was dependent on the effects of treatment, population, line within population and their interaction with maximum value recorded for treatment (93.78%). This study also analyzed heritability of the salt response index (SRI), defined as the ratio between the observed values with and without salt treatment. SRI of most measured traits had high broad-sense heritability (H²). Most of established correlations among SRI values of measured traits were positive. SRI means revealed that, Soliman and Bulla Regia are the most salt-tolerant populations. Based on Ward’s estimated distance, all lines were classified into 4 clusters showing similarity and dissimilarity in response to salt stress. The eco-geographical factors that influence more the variation of SRI of measured traits among populations are assimilated P2O5, % organic matter and carbon and mean annual rainfall. Findings from this study will provide the basis for identifying and breeding of salt-tolerant lines in M. truncatula.Key words: Environmental factors, lines, Medicago truncatula, NaCl stress, populations, quantitative traits

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

The enormous quantity of food wastes discarded annually force to look for alternatives for this interesting feedstock. Thus, food bio-waste valorisation is one of the imperatives of the nowadays society. This review is the most comprehensive overview of currently existing technologies and processes in this field. It tackles classical and innovative physical, physico-chemical and chemical methods of food waste pre-treatment and extraction for recovery of added value compounds and detection by modern technologies and are an outcome of the COST Action EUBIS, TD1203 Food Waste Valorisation for Sustainable Chemicals, Materials and Fuels

SSR marker based DNA fingerprinting of Tunisian olive (Olea europaea L.) varieties

This study aimed to test the efficiency of SSR markers to identify and to differentiate a set of 26 Tunisian olive varieties maintained at four collections. SSR analysis from 10 primer pairs revealed a total of 86 polymorphic alleles with 4 to 14 alleles per locus that allowed unique genotyping of the examined varieties. The Polymorphism Information Content (PIC) values ranged from 0.548 to 0.796 (average 0.719). The efficiency was found very high with average discriminating power overall 10 loci higher than 0.9. A combination of three SSR markers (ssrOeUA-DCA9, ssrOeUA-DCA13 and ssrOeUA-DCA16) was proposed for rapid identification of analysed cultivars. Three cultivars (Gerboui, Ain Jarbouaa and Regregui) thought to be identical resulted in absolutely different SSR profiles. This research showed that SSR is a suitable and effective tool to characterise olive varieties in Tunisian germplasm collections. The outcome of this study could be useful for varietal survey and the construction of a database of all olive varieties in Tunisia

Using microsatellite markers to characterise the main Tunisian cultivars 'Chemlali' and 'Ch\ue9toui'

Twenty-eight accessions of the Tunisian olive (Olea europaea L.) cultivars 'Chemlali' and 'Ch\ue9toui' were screened using 11 microsatellite (SSR) primer pairs to evaluate within-cultivar variability, and to eliminate mis-labelling and redundancies before their introduction into the 'Borj Cedria' olive collection. Variations in microsatellite patterns were observed among accessions under the same denomination. Accessions designated 'Chemlali' showed three different microsatellite profiles, which differed at all loci analysed and should therefore correspond to three different varieties. However, real clonal or intra-cultivar variability was observed in one of the three varieties, as well as in the cultivar 'Ch\ue9toui', with differences between accessions at only one of the 11 loci screened. These results confirm the efficacy of microsatellite (SSR) markers for the classification and selection of olive accessions for germplasm collections

Assessing the drought tolerance of Brachypodium ssp. genotypes by agronomic and physiologic indicators

Abiotic stresses including drought (both in terms of quantity and intensity) are serious threats to the sustainability of crop yields accounting for more crop productivity losses than any other factor in rainfed agriculture. Plant responses to water deficit can be analysed by systematically identifying traits that relate to drought tolerance followed by analysis to the cellular, biochemical and molecular levels. Brachypodium ssp, collected from Northern and central Tunisia, was considered as a potential genetic resource of drought resistance for poaceae and forage species. A group of 180 lines of the Tunisian Brachypodium ssp. representative of 9 populations were tested under three watering regimes: watering after two days, watering after four days and watering after six days. Twelve agronomic and physiologic traits were evaluated for their responses to drought stress on the basis of drought response index (DRI). Results show a considerable variation between genotypes and that the majority of traits showed medium (0.3 to 0.5) to high heritability (> 0.6) with low border value for total number of tiller and high border value for the ratio of productive tiller number per total number of tiller and an average value of 0.46. These findings are encouraging from the point of view of the potential for selecting for improved drought tolerance within that species. The method used allows detection after 3 months' growth of material that has the ability to grow at drought conditions which prevent the growth of other material, and the assumption is that they possess enhanced drought tolerance

Assessment of genetic diversity and population structure of Tunisian populations of Brachypodium hybridum by SSR markers

Brachypodium hybridum has recently been recognized as an allotetraploid species deriving from natural hybridization between B. distachyon and B. stacei. The identification of this species which emerged as a new model for polyploid species has spawned considerable scientific interest. A lot of investigations using highly variable markers and a broad geographical sampling are underway to understand the patterns of their genetic diversity and the contribution of polyploidy to adaptation. As a step towards understanding the genetic basis for natural variation of this species in Tunisia, 15 microsatellite markers and 145 genotypes representing 9 natural populations were used. Results exhibit a high level of polymorphism (159 polymorphic alleles with an average of 8.6 alleles per locus) and high level of genetic diversity in all the studied populations with expected and observed heterozygosities averaging 0.79 and 0.31, respectively. AMOVA resulted in a high variation within population (97%) and altitude as compared to the variation among populations (3%, \u3a6PT=0.023), altitude and eco-region. Results also showed that the 9 populations grouped into 3 clusters without geographical or altitudinal clustering. This grouping was accompanied by a high rate of gene flow between populations (Nm=2.31). Interestingly, Mantel test identified that the extent of genetic differentiation was not correlated to geographic distances (r=0.046; p=0.78) nor to the altitudinal differences (r=-0.29; p=0.75). In the present study we report a high rate of successful cross-amplification of B. distachyon SSR markers in B. hybridum, which implies the great transferability between these two species. Moreover, genetic characterization of the Tunisian populations of B. hybridum by SSR markers suggests that the spatial genetic structure of this species may be affected by a multidirectional gene flow via long-distance seed dispersal, leading to a weak genetic structure