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|Title:||Assess of genetic diversity of Pistacia spp. in wild populations and field gene banks from Central and West Asia||Authors:||Ibrahim Basha, Amer||Keywords:||AGR/07||Issue Date:||9-Mar-2007||Publisher:||Università degli studi della Tuscia - Viterbo||Series/Report no.:||Tesi di dottorato di ricerca. 19. ciclo||Abstract:||
Pistachio (Pistacia vera L.) is one of the most promising nut trees in the Central and West Asia region due to its high nutritional and medicinal value. It is a major crop which contributes to the economy and nutrition of many poor communities in the region. The pistachio crop currently depends on a very narrow genetic base and this constitutes a serious threat to the sustainability of pistachio production in this region. Also traditional cultivars are increasingly being replaced by few improved types in areas of greatest diversity, while the destruction of natural habitats by deforestation, overgrazing, over cutting, and man–made fires contributes to further the loss of wild species. Syria is considered as a center of origin for some Pistacia species. Wild species such as P. atlantica, P. palaestina, P. Khinjuk, and P. terebinthus constitute an important source of genetic diversity for the Pistachio crop. These wild relatives together with local varieties of Pistacia vera form the total Pistacia genetic resources in Syria, which should be maintained for sustainable pistachio cultivation.
Further Syria has about 25 cultivated varieties distinguished by morphological traits. The Pistachio species can be found growing in private farms, forests, national protected areas and national and international field gene banks. Although, Syria is classified as the fourth pistachio producing country in the world, it holds some unique diversity not found elsewhere. Pistachio is a major cash commodity in Iran, Turkey, Syria, Afghanistan and Central Asia on the other hand it could be considered as a neglected and under utilized genetic resources having high income potential. On the other hand, the pure stand of the P. vera in central Asia, center of origin, makes the area a valuable source of the genetic diversity but unfortunately a severe forest degradation affected these population.
The purpose of this research is to assess the level of diversity of the Pistacia gene pool conserved in both ex situ and in situ/on farm in Syria, Uzbekistan and Tajikistan using molecular techniques in order to better understand the genetic structure, pattern and distribution of diversity within ex situ collections and in the wild and to develop a complementary conservation and use strategy for pistachio. This research was carried out during 2004-2006.
In this study, the distribution and diversity conservation of cultivated and wild populations of Pistacia species in the Central and West Asia have been examined. A based ecogeographic survey was first undertaken to determine the distribution of the different Pistacia genus in Central and West Asia, principally in Syria, Tajikistan and Uzbekistan. Fifty four sites were chosen to represent the distribution of these species and to collect the plant material in order to be characterized and evaluated. Then several visits were paid these sites, the results of this study showed that the Pistacia genus was found in different climatic areas ranged from dry up to humid areas. These results indicate the pistachio is a drought resistant tree and flourishing in arid and semi-arid zones. Pistacia genus were found in a margin areas with wide range of soils, especially in those very shallow, moderately developed, non-acid with clay-enriched subsoil, and also on no significant soil profile development or poorly developed soils of semi-deserts.
All surveyed accessions were thoroughly studied to assess their morphological variability. Characters related to the tree growth, leaves, nuts, were among those considered during these evaluations. The Descriptor Lists produced by IPGRI (1997; 1998) were adopted in these activities. The results pf this studied showed a highly significant variability between and within these species, due to there environmental conditions.
AFLP, ISSR, SSR molecular analyses and multivariate (Factor Analysis Principal Component) and cluster analysis showed a large amount of variability both within and between species in the wild populations of Pistacia in this region. The correlations between the data of these three molecular markers techniques were either significant or highly significant. This study confirms that P. terebinthus and P. palaestina had a close relationship with all Molecular techniques applied which is adopted the opinion of being P. palaestina as subspecies of P. terebinthus. On the other hand the principle component analysis found that these species could be clustered in three main groups, first with P. atlantica and P. khinjuk, the second contained the wild and cultivated P. vera and the third groups contained P. palaestina and P. terebinthus. While P. lentiscus the only evergreen species never grouped with any of the pervious groups.
The data obtained from the ecogeogarphic survey were compared with those of each molecular marker technique, the results found the existence of significant correlations between the climate and the molecular marker data which are applied on Pistacia species ranged between highly significant with Pistacia vera case with all markers or significant and not correlated in other species and markers. The quantitive morphological characters of leaves and nuts were also compared with the molecular markers data for male and female groups in each site. The results showed that there are no correlations between the leaves and leaflets dimensions and any of the used molecular marker techniques with any molecular marker technique, with some exception for SSR technique and the nut dimensions in P. palaestina and P. terebinthus, which were significantly correlated.
Finally this study discussed a suggested complementary conservation strategy according to the results obtained from this study and the possibilities available in these countries. Four possible conservation methods were being most recommended according to the conditions of the Pistacia genus. Two ex situ conservation methods which are conventional seed storage and field gene banks are the most suitable ways to conserve the Pistacia spp. On the other hand, Biosphere reserves or protected areas and on farm conservation are the most convenient in situ conservations for these species. The combination of these four methods would overpass the disadvantage of some of them such as the static conservation of the seed storage or the possible loss of the diversity in the cultivated pistachio if the on-farm conservation was involved.
The achieved objectives of this study is the result of a successful joint cooperation between the Department of Agrobiology and Agrochemical of the Faculty of Agriculture, University of Tuscia, and the CGIAR scientists in Bioversity International, International Center for Agricultural Research in the Dry Areas ICARDA and Bioversity International the regional office for Central, West Asia and North Africa (CWANA).
Dottorato di ricerca in Genetica agraria
|Appears in Collections:||Archivio delle tesi di dottorato di ricerca|
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