1. Genetic diversity of Pyrenophora tritici-repentis in Algeria as revealed by amplified fragment length polymorphism (AFLP) analysis ( 1)Ecole Nationale Supérieure d’Agronomie, Département de Botanique, El-Harrach, Alger, Algeria. h.benslimane@ensa.dz. (2) International Maize and Wheat Improvement Center, Apdo. Postal 6-641,06600, Mexico DF, Mexico. (3) International Center for Agricultural Research in Dry Areas, P.O. Box 5466, Aleppo Syria. Hamida BENSLIMANE 1, Amor YAHYAOUI 2, Francis OGBONNAYA 3, Zouaoui BOUZNAD 1 and Micheal BAUM 3 Abstract Tan spot caused by Pyrenophora tritici-repentis is a major wheat disease. DNA of 61 isolates from different cereal growing areas in Algeria were analyzed using florescent AFLP. Initially, 78 primer combinations were tested, of which 12 were selected and applied to the 61 isolates. There was a high genetic diversity in this population with 61 different haplotypes. The Jaccard similarity index range was 1.43 to 68.37%. Cluster analysis showed that, clustering of isolates was independent of their race classification, geographic origin, or host plant. However, one isolate (Ptr24) that showed a new virulence pattern in our previous race analysis study was clearly distinguished from the rest of the population studied. This isolate had not only new virulence but also different genetic makeup to other isolates and requires additional studies to decipher complete knowledge of host-pathogen interactions for tan spot of wheat. Abstract Tan spot caused by Pyrenophora tritici-repentis is a major wheat disease. DNA of 61 isolates from different cereal growing areas in Algeria were analyzed using florescent AFLP. Initially, 78 primer combinations were tested, of which 12 were selected and applied to the 61 isolates. There was a high genetic diversity in this population with 61 different haplotypes. The Jaccard similarity index range was 1.43 to 68.37%. Cluster analysis showed that, clustering of isolates was independent of their race classification, geographic origin, or host plant. However, one isolate (Ptr24) that showed a new virulence pattern in our previous race analysis study was clearly distinguished from the rest of the population studied. This isolate had not only new virulence but also different genetic makeup to other isolates and requires additional studies to decipher complete knowledge of host-pathogen interactions for tan spot of wheat. Literature sited 1.Benslimane H., L. Lamari, A. Benbelkacem, R. Sayoud and Z. Bouznad, 2011. Distribution of races of Pyrenophora tritici-repentis in Algeria and identification of a new virulence type. Phytopathologia Mediterranea, 50: 203−211. 2.Benslimane H., S. Lababidi, A. Yahyaoui, F. Ogbonnaya, Z. Bouznad and M. Baum. 2013. “Genetic diversity of Pyrenophora tritici-repentis in Algeria as revealed by amplified fragment length polymorphism (AFLP) analysis”, African Journal of Biotechnology.12 (28). p.p. 4082-4093. Wheat growing areas where isolates were collected Similarity matrix in percentage using the similarity coefficient of Jaccard 1.43% - 68.37% High diversity Ptr24? Low values (1.83- 16.43%) High molecular diversity within the population was noted  Clustering was independent of race classification  Isolates belonging to the new virulence pattern could be distinguished from other isolates with percentages of similarity ≤ 50%  Ptr24 differed greatly from the other isolates (8% of similarity). Well supported by bootstrap values of 100%. Ptr24-new virulence pattern Dendogram produced using UPGMA cluster analysis based on Jaccard similarity coefficient calculated from AFLP DNA fragments from the isolates which the race classification is know Florescent AFLP analysis DNA was digested using the restriction enzymes EcoRI and MseI. Complementary EcoRI and MseI were used without base extension Pre amplification step was performed using pre-selective primers (EcoRI+0) and (MseI+0) Selective amplification was performed with MseI primers and fluorescently marked EcoRI primers. 78 combinations of primers were tested and 12 pairs were selected Amplification products were separated by capillary electrophoresis in an ABI PRISM 3100 Fungal isolates Fungal DNA extraction Primers combinations The PIC mean values of the loci generated by each primers combination C70 and C11 showed the most informative values. For further analysis, it will be possible to choose a lower number of markers 1 3 2 This work is the first study of genetic diversity of P. tritici-repentis in Algeria; a high level of genetic variability was demonstrated between the isolates analyzed. It provides information about genetic structure of this population which should be used by plant breeders. In fact, pathogen populations with large genetic variation gain advantage as they can rapidly respond to changing environments and overcome host resistance and fungicide treatments. Conclusion 4 Dendogram produced using UPGMA cluster analysis based on Jaccard similarity coefficient calculated from AFLP DNA fragments from all the isolates (?=new virulence pattern). To produce mycelia, isolates were grown in Fries liquid medium. DNA extraction was made following Phenol/Chloroform method as was reported in Benslimane et al. (2013). 61 isolates of P. tritici-repentis, were obtained from several infected fields (Durum and bread wheat) in different cereal growing areas in Algeria and their race type was identified as described in Benslimane et al.(2011). Scientific Method  The cluster analysis revealed 2 main groups at the level of linkage distance of 6%  The first group was formed by a single isolate Ptr30  The second cluster included the rest of the isolates; with several identifiable groups at different levels of linkage, regardless of host species or geographical origin.  Isolates from different locations were found in the same clusters.  Isolates from durum and bread wheat were found together in the same cluster.  Isolates from the same leaf spot were classified into different clusters (Ptr73,Ptr75,Ptr76) (linked only on at a level of 17% of similarity) High molecular diversity and clustering of isolates was independent of their geographic origin, or host plant……..? (*) kind of fluorophore NED VIC FAM Results