Genetic Structure of Setosphaeria turcica Populations in Tropical and Temperate Climates

Abstract

Northern leaf blight, caused by Setosphaeria turcica, is a serious disease of maize in temperate and tropical environments. To examine the pathogen's population structure, we analyzed 264 isolates from four different continents with 70 random amplified polymorphic DNA markers and determined their mating types. Tropical populations (from Kenya, Mexico, and southern China) had an extremely high genotypic diversity, no or only weak gametic phase disequilibrium, and an even distribution of the two mating types, indicating frequent sexual recombination. Temperate populations (from Europe and northern China) had a much lower genotypic diversity, strong gametic phase disequilibrium, and an uneven distribution of mating types, indicating that sexual recombination has been rare. Populations in different continents were genetically isolated. They shared no haplotypes and carried several "private" alleles. The number of migrants between continents and between regions (between northern and southern China, western and central Kenya, and Europe west and east of the Alps) was estimated to be less than one per generation. Multivariate statistics suggested a greater relatedness of populations from the same continents than from different continents. Within agroecological zones, migration must be extensive. The potential within populations of S. turcica for adaptation should be regarded as very high, especially in tropical climates.

Geographic Distribution and Genetic Analysis of Physiological Racesof Setosphaeria turcica in Northern China

“…The studies on the genetic variation within and between race groups in Northern China by RAPD analysis revealed that the pathogen's population had high genotypic diversity, which was identical to the studies of genetic structure of Setosphaeria turcica populations in tropical and temperate climates [9] . Genetic variation within race groups suggested that the race groups were genetic similar within one location, but it could not be excluded that genetic migration could happen between locations.…”

“…In the United States, northern leaf blight was the major disease of maize [31] . However, after the seven races 0, 1, 2, N, 23, 2N and 23N were reported [4,13] , even the great variation in genetic diversity of the pathogen was found within or between states or regions [9,32] , only Oliari et al [33] reported three new races including two new virulent factors in S. turcica. One of the major reasons for the little discovery of new physiological races could be predicated as the even distribution of corn lines with different resistant genes leading to balanced genetic differentiation in Setosphaeria turcica, which could be suggested by the genetic variation studies within and between race groups in this project.…”

“…The use of RAPD (random amplification of polymorphic DNA) markers was widely used in taxonomy and genetic variance of microbial populations and was ever applied to study the genetic polymorphism of S. turcica in Africa and Isalel [8] , in tropical and temperate [9] and in Europe [10] . The studies enhanced the ability to make inferences about phylogeny and provided vital information about possible genetic mechanisms of S. turcica.…”

Microbial Biodiversity: Approaches to Experimental Design and Hypothesis Testing in Primary Scientific Literature from 1975 to 1999

“…Population variance must be measured from multiple samples from the same population. Alternatively, some authors have exploited methods proposed for estimating the theoretical variance of composite diversity indices via simulation or calculations (25,276,277). Hence, for diversity based on Nei's index, Chen et al (40) used parametric tests (t tests) to evaluate differences in genetic diversity for situations in which they had measures of variance.…”

Les Méthodes Moléculaires Pour La Caractérisation Des Champignons Phytopathogènes

“…Elle a été utilisée afin d'évaluer le niveau de la diversité génétique entre les races de plusieurs champignons phytopathogènes (Chen et al, 1993 ;Kolmer et al, 1995 ;Borchardt et al, 1998 ;Gonzalez et al, 1998 ;Hamelin et al, 1998). Elle a également été l'outil d'identification et de discrimination entre les pathotypes d'autres espèces (Kelly et al, 1994 ;Goodwin et Annis, 1991 ).…”