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El Khaldi R.,Center Regional Of Recherche En Agriculture Oasienne | Daami-Remadi M.,University of Sousse | Cherif M.,Center technique des agrumes
Journal of Phytopathology | Year: 2016

The suppressive effects of two different types of date palm composts and some of their indigenous microorganisms were evaluated in vitro and on potato plants inoculated with Rhizoctonia solani. Fungi isolated from composts screened against R. solani by dual cultural assays on PDA showed a significant inhibition of pathogen mycelium growth as compared with untreated control. The type of hyphal interactions between R. solani and each tested antagonist was observed by light microscopy. Microscopic observations carried out at the confrontation zone of both agents showed different mechanisms of actions: mycelia lyses, mycoparasitism and/or formation of mycelia cords via anatomosis between mycelia filaments. Unsterilized and sterilized compost extracts were tested for efficacy against R. solani using agar-well diffusion method or by pouring the extracts on PDA. Two sterilization methods were used: a filtration through a microfilter of 0.22 microns or autoclaving. Results showed that compost extract lost its activity after heating or filtration, confirming that chemical factors in compost had no direct inhibiting effect on the pathogen. The suppressiveness of composts was mainly due to their biotic component. Series of greenhouse trials showed that black scurf and stem canker incidence and severity were significantly reduced in peat-sand amended with compost compared with the untreated control. However, the potential suppressive effect of cattle manure and date palm compost (CMC) was higher than sheep manure and date palm compost (SMC). On potato seed tubers pre-inoculated with the selected fungal isolates from compost, there was variability in the reduction of disease severity among treatments. Plant growth was unaffected by the application of fungal antagonists or by CMC amendment; however, an increase in the total yield was observed by the SMC potting mix compared with untreated control. © 2016 Blackwell Verlag GmbH. Source


Zehdi-Azouzi S.,Tunis el Manar University | Cherif E.,Tunis el Manar University | Cherif E.,IRD Montpellier | Guenni K.,Tunis el Manar University | And 8 more authors.
Genetica | Year: 2016

The breeding of crop species relies on the valorisation of ancestral or wild varieties to enrich the cultivated germplasm. The Tunisian date palm genetic patrimony is being threatened by diversity loss and global climate change. We have conducted a genetic study to evaluate the potential of spontaneous coastal resources to improve the currently exploited Tunisian date palm genetic pool. Eighteen microsatellite loci of Phoenix dactylifera L. were used to compare the genetic diversity of coastal accessions from Kerkennah, Djerba, Gabès and continental date palm accessions from Tozeur. A collection of 105 date palms from the four regions was analysed. This study has provided us with an extensive understanding of the local genetic diversity and its distribution. The coastal date palm genotypes exhibit a high and specific genetic diversity. These genotypes are certainly an untapped reservoir of agronomically important genes to improve cultivated germplasm in continental date palm. © 2016 Springer International Publishing Switzerland Source


Zehdi-Azouzi S.,Tunis el Manar University | Cherif E.,Tunis el Manar University | Cherif E.,IRD Montpellier | Moussouni S.,University of Science and Technology Houari Boumediene | And 22 more authors.
Annals of Botany | Year: 2015

Background and Aims Date palms (Phoenix dactylifera, Arecaceae) are of great economic and ecological value to the oasis agriculture of arid and semi-arid areas. However, despite the availability of a large date palm germplasm spreading from the Atlantic shores to Southern Asia, improvement of the species is being hampered by a lack of information on global genetic diversity and population structure. In order to contribute to the varietal improvement of date palms and to provide new insights on the influence of geographic origins and human activity on the genetic structure of the date palm, this study analysed the diversity of the species. Methods Genetic diversity levels and population genetic structure were investigated through the genotyping of a collection of 295 date palm accessions ranging from Mauritania to Pakistan using a set of 18 simple sequence repeat (SSR) markers and a plastid minisatellite. Key Results Using a Bayesian clustering approach, the date palm genotypes can be structured into two different gene pools: the first, termed the Eastern pool, consists of accessions from Asia and Djibouti, whilst the second, termed the Western pool, consists of accessions from Africa. These results confirm the existence of two ancient gene pools that have contributed to the current date palm diversity. The presence of admixed genotypes is also noted, which points at gene flows between eastern and western origins, mostly from east to west, following a human-mediated diffusion of the species. Conclusions This study assesses the distribution and level of genetic diversity of accessible date palm resources, provides new insights on the geographic origins and genetic history of the cultivated component of this species, and confirms the existence of at least two domestication origins. Furthermore, the strong genetic structure clearly established here is a prerequisite for any breeding programme exploiting the effective polymorphism related to each gene pool. © 2015 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. Source

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