Genotypic Diversity of the Wheat leaf blotch pathogen ( Septoria tritici ) in Buenos Aires Province Diversidad genotípica del patógeno de la mancha de la hoja del trigo ( Septoria tritici ) en la provincia de Buenos Aires

The population structure and genotypic diversity of Septoria tritici Rob ex Desm. from two crop field populations in Buenos Aires Province were studied with DNA restriction fragment length polymorphism. Hierarchical samples were taken from different cultivars. A total of 120 single spore isolates was subject to molecular analysis to compare the genetic structure of Los Hornos and Balcarce populations separated by 500km. Eight RFLP loci and 1DNA fingerprinting were used. Among the total of the isolates, 24 RFLP alleles were detected from the first population and 22 from the second. Gene and genotype diversity were high in both populations. Different haplotypes for each region were identified. Identical haplotypes were clustered in the same location in the field. The mean gene diversity and the mean genotypic diversity were high for the 8 loci of RFLP. This means that Balcarce and Los Hornos were significantly different. The X 2 was significant (P>0.005) only for two RFLP locus, then both populations were not independant. They had to be compared with an European and an American populations. Balcarce population was very different to all of them. Both Argentine populations were very similar at regional level but strongly different at a continental level. The greatest genetic variability between continents belonged to Argentine population. The amount of gene flow was high when all the populations were compared.<br>Se estudió la estructura poblacional y la diversidad genética y genotípica de dos poblaciones de Septoria tritici Rob ex Desm. con la técnica de RFLP Un total de 120 aislamientos monospóricos colectada en campos experimentales de la Provincia de Buenos Aires se analizaron molecularmente, comparando la estructura genética de dos poblaciones separadas por 500 km . Se experimentó con 8 loci de RFLP y una sonda de ADN fingerprinting. Sobre la totalidad de los aislamientos se detectaron 24 alelos de RFLP para la localidad de Los Hornos y 22 para Balcarce. En la población de Los Hornos entre 58 aislamientos se reconocieron 35 haplotipos multilocus y en Balcarce, entre 62 aislamientos, 39 haplotipos, significando que ambas poblaciones son diferentes. Las diversidades genética y genotípica fueron altas en ambas poblaciones. La diferencia entre poblaciones, para las frecuencias de alelos, se calculó con el test de contingencia X 2 ; como estas fueron solo significativas para dos locus de RFLP (P>0.005) se procedió a comparar las poblaciones locales con una de europea y otra americana. Las poblaciones en Argentina fueron muy distintas a las otras poblaciones analizadas. Se interpretó que las poblaciones argentinas fueron similares a nivel regional pero difirieron significativamente de las de Suiza y Oregón, para los loci analizados.