Molecular variance of the Tunisian almond germplasm assessed by simple sequence repeat (SSR) markers

The genetic variance analysis of 82 almond (Prunus dulcis Mill.) genotypes was performed using ten genomic simple sequence repeats (SSRs). A total of 50 genotypes from Tunisia including local landraces identified while prospecting the different sites of Bizerte and Sidi Bouzid (Northern and central parts) which are the most important locations of almond diversity in Tunisia were included. Analysis of molecular variance (AMOVA) was  performed for 11 populations from these different regions and foreign countries to examine the distribution of genetic variation of the accessions studied. Results show that the major variation occurred within populations in each geographic site. Additionally, this analysis demonstrates that the genetic diversity within local almond cultivars was important, with a clear geographic distinction between the Northern and the Southern Tunisian cultivars. The value of prospecting new sites, preserving genetic diversity and encouraging on farmers almond collections is also discussed.Keywords: Prunus dulcis Mill., Genetic resources, AMOVA, local ecotypes, geographic origin, TunisiaAfrican Journal of Biotechnology Vol. 12(29), pp. 4569-457

Usefulness of microsatellites for positioning the tunisian almond germplasm in its mediterranean geographic context.

6 Pags.- 1 Tabl.- 1 Fig. The definitive version is available at: http://www.actahort.org/index.htmIn Tunisia, the almond tree (Prunus dulcis), dating back to ancient times, has been grown extensively since the Carthaginian era. In the framework of a national project on the characterisation and the conservation of the local almond germplasm many morphological and molecular markers (RAPD and SSR) have been used in order to analyse the genetic diversity of the main almond cultivars and to seek for the genetic position of these resources in the Mediterranean basin. For this study, 10 SSRs were used to analyse 82 almond accessions from different origins. Most of them originated from Tunisia (50), the others included in the National collection were from France (9), Italy (7), Morocco (1), Spain (8), USA (3), or were of unknown origin (4). The dendrogram based on UPGMA analysis using the similarity matrix generated by the Nei and Li (1979) coefficient presented four main clusters (A, B, C and D). In group A were present 40 of the 50 local genotypes that originate from the centre and the south contrarily, all cultivars from the north were in group C and clustered with the European and American genotypes. Accordingly, our study stressed the large diversity of the Tunisian almonds and revealed the presence of two distinct genetic groups. One located in the north genetically close to the gene pool of the Northern border of the Mediterranean and the second in the central and southern part that is highly adapted to different abiotic stress mainly drought.Peer reviewe

The root transcriptome dynamics reveals new valuable insights in the salt-resilience mechanism of wild grapevine (Vitis vinifera subsp. sylvestris)

Introduction: Most of elite cultivated grapevine varieties (Vitis vinifera L.), conventionally grafted on rootstocks, are becoming more and more affected by climate changes, such as increase of salinity. Therefore, we revisited the valuable genetic resources of wild grapevines (V. sylvestris) to elaborate strategies for a sustainable viticulture. Methods: Here, we compared physiological and biochemical responses of two salt-tolerant species: a wild grapevine genotype “Tebaba” from our previous studies and the conventional rootstock “1103 Paulsen”. Interestingly, our physio-biochemical results showed that under 150mM NaCl, “Tebaba” maintains higher leaf osmotic potential, lower Na+/K+ ratio and a significant peaked increase of polyphenol content at the first 8h of salinity stress. This behavior allowed to hypothesis a drastic repatterning of metabolism in “Tebaba’s” roots following a biphasic response. In order to deepen our understanding on the “Tebaba” salt tolerance mechanism, we investigated a time-dependent transcriptomic analysis covering three sampling times, 8h, 24h and 48h. Results: The dynamic analysis indicated that “Tebaba” root cells detect and respond on a large scale within 8h to an accumulation of ROS by enhancing a translational reprogramming process and inducing the transcripts of glycolytic metabolism and flavonoids biosynthesis as a predominate non-enzymatic scavenging process. Afterwards, there is a transition to a largely gluconeogenic stage followed by a combined response mechanism based on cell wall remodeling and lignin biosynthesis with an efficient osmoregulation between 24 and 48 h. Discussion: This investigation explored for the first time in depth the established cross-talk between the physiological, biochemical and transcriptional regulators contributing to propose a hypothetical model of the dynamic salt mechanism tolerance of wild grapevines. In summary, these findings allowed further understanding of the genetic regulation mechanism of salt-tolerance in V. sylvestris and identified specific candidate genes valuable for appropriate breeding strategies

Climatic Aridity Gradient Modulates the Diversity of the Rhizosphere and Endosphere Bacterial Microbiomes of Opuntia ficus-indica

© Copyright © 2020 Karray, Gargouri, Chebaane, Mhiri, Mliki and Sayadi. Recent microbiome research has shown that soil fertility, plant-associated microbiome, and crop production can be affected by abiotic environmental parameters. The effect of aridity gradient on rhizosphere-soil (rhizosphere) and endosphere-root (endosphere) prokaryotic structure and diversity associated with cacti remain poorly investigated and understood. In the current study, next-generation sequencing approaches were used to characterize the diversity and composition of bacteria and archaea associated with the rhizosphere and endosphere of Opuntia ficus-indica spineless cacti in four bioclimatic zones (humid, semi-arid, upper-arid, and lower-arid) in Tunisia. Our findings showed that bacterial and archaeal cactus microbiomes changed in inside and outside roots and along the aridity gradient. Plant compartment and aridity gradient were the influencing factors on the differentiation of microbial communities in rhizosphere and endosphere samples. The co-occurrence correlations between increased and decreased OTUs in rhizosphere and endosphere samples and soil parameters were determined according to the aridity gradient. Blastococcus, Geodermatophilus, Pseudonocardia, Promicromonospora, and Sphingomonas were identified as prevailing hubs and were considered as specific biomarkers taxa, which could play a crucial role on the aridity stress. Overall, our findings highlighted the prominence of the climatic aridity gradient on the equilibrium and diversity of microbial community composition in the rhizosphere and endosphere of cactus.We thank the Tunisian authorities for the support in prickly pear tree sampling and also Dr. Fabrice Armougoum from the Mediterranean Institute of Oceanography (MIO, IRD, UM 110, 13288, Marseille, France) for his great help on microbiome analysis

Olive agroforestry shapes rhizosphere microbiome networks associated with annual crops and impacts the biomass production under low-rainfed conditions

Agroforestry (AF) is a promising land-use system to mitigate water deficiency, particularly in semi-arid areas. However, the belowground microbes associated with crops below trees remain seldom addressed. This study aimed at elucidating the effects of olive AF system intercropped with durum wheat (Dw), barely (Ba), chickpea (Cp), or faba bean (Fb) on crops biomass and their soil-rhizosphere microbial networks as compared to conventional full sun cropping (SC) under rainfed conditions. To test the hypothesis, we compared the prokaryotic and the fungal communities inhabiting the rhizosphere of two cereals and legumes grown either in AF or SC. We determined the most suitable annual crop species in AF under low-rainfed conditions. Moreover, to deepen our understanding of the rhizosphere network dynamics of annual crops under AF and SC systems, we characterized the microbial hubs that are most likely responsible for modifying the microbial community structure and the variability of crop biomass of each species. Herein, we found that cereals produced significantly more above-ground biomass than legumes following in descending order: Ba > Dw > Cp > Fb, suggesting that crop species play a significant role in improving soil water use and that cereals are well-suited to rainfed conditions within both types of agrosystems. The type of agrosystem shapes crop microbiomes with the only marginal influence of host selection. However, more relevant was to unveil those crops recruits specific bacterial and fungal taxa from the olive-belowground communities. Of the selected soil physicochemical properties, organic matter was the principal driver in shaping the soil microbial structure in the AF system. The co-occurrence network analyses indicated that the AF system generates higher ecological stability than the SC system under stressful climate conditions. Furthermore, legumes’ rhizosphere microbiome possessed a higher resilient capacity than cereals. We also identified different fungal keystones involved in litter decomposition and drought tolerance within AF systems facing the water-scarce condition and promoting crop production within the SC system. Overall, we showed that AF reduces cereal and legume rhizosphere microbial diversity, enhances network complexity, and leads to more stable beneficial microbial communities, especially in severe drought, thus providing more accurate predictions to preserve soil diversity under unfavorable environmental conditions.This research was carried out as part of the D4DECLIC Project, ARIMNet 2 Young Scientists Call 2017 (ERA-NET program), and Grant agreement no. 618127

Fertiledatepalm – a transdisciplinary collaboration project to ameliorate date palm cultivation via microbial inoculation, organic matter management and mixed cropping using nurse plants

Date palm is an important crop in Morocco, Tunisia and other drylands with a high agricultural, economic and cultural value. Harsh environmental conditions of those areas, further accelerated by climate change and the spread of root diseases, threaten date palm cultivation. To overcome limitations in productivity, high inputs of mineral fertilizers and pesticides are applied. However, these external inputs strongly affect the environment and livelihoods. The project aims at establishing an integrated microbe-assisted fertilization approach, combining the inoculation of native soil microbes, namely arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) during the different date palm growth stages, with adapted agricultural management practices using organic amendments and mixed-cropping in Morocco and Tunisia. As initial step, we established a culture collection of native microbes, isolated from date palm roots and rhizosphere composed of 24 AMF isolates including eight species from six genera, twelve bacterial endophyte isolates composed of Paenibacillus, Mycobacterium, and Achromobacter species and 34 PGPR isolates. Functional characterization of PGPRs revealed that around 50 % can solubilize phosphorus and potassium and between 9 % and 68 % have the ability to produce siderophores, hydrogen cyanid, chitinase, cellulase, amylase and protease. Consortia of microbes were formed and used for inoculations. Experiments under nursery conditions revealed that inoculation with AMF and PGPR combined with compost significantly increased growth of date palms as compared to non-amended controls enabling farmers to decrease the time prior to field transplantation. On-farm trials performed in productive date palm groves have shown that PGPR inoculation with or without mixed-cropping with sorghum as nurse plants significantly increase fruit characteristics such as fruit flesh weight as well as fruit length and diameter for up to 14 % and leaf macronutrient concentrations for up to 200 % while in addition enhancing the mycorrhizal potential of the soil. Our integrated fertilization approach is developed in a participatory approach with key stakeholders in so-called innovation platforms, working at laboratory, on-station and on-farm scale to best tackle farmers’ needs in order to facilitate adoption and implementation

Harnessing rhizospheric core microbiomes from arid regions for enhancing date palm resilience to climate change effects

Date palm cultivation has thrived in the Gulf Cooperation Council region since ancient times, where it represents a vital sector in agricultural and socio-economic development. However, climate change conditions prevailing for decades in this area, next to rarefication of rain, hot temperatures, intense evapotranspiration, rise of sea level, salinization of groundwater, and intensification of cultivation, contributed to increase salinity in the soil as well as in irrigation water and to seriously threaten date palm cultivation sustainability. There are also growing concerns about soil erosion and its repercussions on date palm oases. While several reviews have reported on solutions to sustain date productivity, including genetic selection of suitable cultivars for the local harsh environmental conditions and the implementation of efficient management practices, no systematic review of the desertic plants’ below-ground microbial communities and their potential contributions to date palm adaptation to climate change has been reported yet. Indeed, desert microorganisms are expected to address critical agricultural challenges and economic issues. Therefore, the primary objectives of the present critical review are to (1) analyze and synthesize current knowledge and scientific advances on desert plant-associated microorganisms, (2) review and summarize the impacts of their application on date palm, and (3) identify possible gaps and suggest relevant guidance for desert plant microbes’ inoculation approach to sustain date palm cultivation within the Gulf Cooperation Council in general and in Qatar in particular

Action d'un Pseudomonas sp sur des lignines de bois explose et divers derives benzyliques

SIGLEINIST T 71051 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc