Growing pear has a long tradition in Tunisia, and numerous local cultivars possessing an excellent adaptability and resilience potential to climatic variation are present. This large adaptability is associated with an...Growing pear has a long tradition in Tunisia, and numerous local cultivars possessing an excellent adaptability and resilience potential to climatic variation are present. This large adaptability is associated with an important genetic diversity, which is threatened to erosion.Appropriate measures have to be taken in order to properly evaluate and conserve this local material. Microsatellite markers were used to assess the level of genetic diversity among Tunisian pear germplasm, and compare it with some European varieties and wild pear species. 61 pear accessions representing eight groups(six groups from Tunisia, one from Northern Europe and another group composed of wild pear) have been genotyped using SSR markers derived from apple and pear. The pear accessions showed a significant polymorphism and 95 polymorphic alleles were found. The number of alleles per locus varied from 5 for CH04e03 locus to 14 for CH01d09 locus with an average of 9.4 alleles per locus.Moreover, the mean gene diversity(H_e) per locus ranged from 0.192 to 0.752. Genetic distance values and cluster analyses revealed high genetic similarities among the Tunisian groups. Factorial correspondence analysis(FCA) categorized the accessions into three independent groups where Tunisian local accessions agglomerated together distantly from European and wild pear accessions. Additionally, UPGMA dendrogram grouped accessions into two clusters, confirmed thereafter by the Bayesian model-based Structure analysis. The results showed 16 putative triploid accessions found in the local germplasm. This study provides valuable information to develop strategies of local pear conservation and use.展开更多
Fifteen expressed sequence tag (EST)-derived simple sequence repeats (EST-SSRs) were used to investigate genetic diversity in 139 plants obtained from seeds of 35 watermelon accessions collected from all the geographi...Fifteen expressed sequence tag (EST)-derived simple sequence repeats (EST-SSRs) were used to investigate genetic diversity in 139 plants obtained from seeds of 35 watermelon accessions collected from all the geographical provinces of Zimbabwe. In addition, 15 plants representing three commercial varieties developed in the United States (USA) were analyzed for comparison. A total of 65 alleles were detected among all the watermelon accessions. For the 13 polymorphic EST-SSR loci, number of alleles per locus varied from 2 to 13, with an average of 5 alleles per locus. Values for the polymorphic information content increased as the number of alleles increased, and varied from 0.15 to 0.77 with an average of 0.54 suggesting sufficient discriminatory power. Both cluster analysis and principal coordinate analysis (PCA) produced two major clusters;one with the 22 cow-melon accessions and the other with the 16 sweet watermelon accessions. Within the sweet watermelon group, two distinct sub-clusters formed, one of which contained only two of the commercial varieties from USA. Partitioning of genetic variation in the Zimbabwean material using analysis of molecular variation (AMOVA) revealed that 64% of the total variation resides between the two major forms, i.e. sweet watermelons and cow-melons, 28% between accessions within forms and 8% within accessions. The EST-SSR markers revealed a somewhat higher diversity in sweet watermelon accessions compared to that of cow-melons. This finding is contrary to previous reports using other markers (genomic SSR loci or RAPD) and/or a plant material that is likely to have experienced more stringent selection procedures compared to the landraces analyzed in our study.展开更多
基金Rim Ouni’s scientific study in Alnarp(Sweden)was supported by a grant from the Tunisian Ministry of Higher Education and Scientific Research(Bourse d’alternance).Authors are grateful to Department of Plant Breeding of Swedish University of Agricultural Sciences SLU(both Alnarp and Balsgard)for technical and financial support.Also,comments received from Prof.Hilde Nybon are greatly appreciated.
文摘Growing pear has a long tradition in Tunisia, and numerous local cultivars possessing an excellent adaptability and resilience potential to climatic variation are present. This large adaptability is associated with an important genetic diversity, which is threatened to erosion.Appropriate measures have to be taken in order to properly evaluate and conserve this local material. Microsatellite markers were used to assess the level of genetic diversity among Tunisian pear germplasm, and compare it with some European varieties and wild pear species. 61 pear accessions representing eight groups(six groups from Tunisia, one from Northern Europe and another group composed of wild pear) have been genotyped using SSR markers derived from apple and pear. The pear accessions showed a significant polymorphism and 95 polymorphic alleles were found. The number of alleles per locus varied from 5 for CH04e03 locus to 14 for CH01d09 locus with an average of 9.4 alleles per locus.Moreover, the mean gene diversity(H_e) per locus ranged from 0.192 to 0.752. Genetic distance values and cluster analyses revealed high genetic similarities among the Tunisian groups. Factorial correspondence analysis(FCA) categorized the accessions into three independent groups where Tunisian local accessions agglomerated together distantly from European and wild pear accessions. Additionally, UPGMA dendrogram grouped accessions into two clusters, confirmed thereafter by the Bayesian model-based Structure analysis. The results showed 16 putative triploid accessions found in the local germplasm. This study provides valuable information to develop strategies of local pear conservation and use.
文摘Fifteen expressed sequence tag (EST)-derived simple sequence repeats (EST-SSRs) were used to investigate genetic diversity in 139 plants obtained from seeds of 35 watermelon accessions collected from all the geographical provinces of Zimbabwe. In addition, 15 plants representing three commercial varieties developed in the United States (USA) were analyzed for comparison. A total of 65 alleles were detected among all the watermelon accessions. For the 13 polymorphic EST-SSR loci, number of alleles per locus varied from 2 to 13, with an average of 5 alleles per locus. Values for the polymorphic information content increased as the number of alleles increased, and varied from 0.15 to 0.77 with an average of 0.54 suggesting sufficient discriminatory power. Both cluster analysis and principal coordinate analysis (PCA) produced two major clusters;one with the 22 cow-melon accessions and the other with the 16 sweet watermelon accessions. Within the sweet watermelon group, two distinct sub-clusters formed, one of which contained only two of the commercial varieties from USA. Partitioning of genetic variation in the Zimbabwean material using analysis of molecular variation (AMOVA) revealed that 64% of the total variation resides between the two major forms, i.e. sweet watermelons and cow-melons, 28% between accessions within forms and 8% within accessions. The EST-SSR markers revealed a somewhat higher diversity in sweet watermelon accessions compared to that of cow-melons. This finding is contrary to previous reports using other markers (genomic SSR loci or RAPD) and/or a plant material that is likely to have experienced more stringent selection procedures compared to the landraces analyzed in our study.
