Population structure of Mycosphaerella graminicola and location of genes for resistance to the pathogen in several wheat populations. Recent advances in Argentina

M. R. SIMÓN, N. CASTILLO, C. CORDO, A. BÖRNER

México DF

Simposio; 8th International Symposium on Mycosphaerella and Stagonospora Diseases of Cereals; 2011

CIMMYT (Centro Internacional de Mejoramiento de Maíz y Trigo)

Sub-region IV (SE of Buenos Aires Province) and II South (central part of Buenos Aires Province) with ten ISSR primers. A high degree of genetic diversity was found: 81 different haplotypes among the 126 isolates studied. A high gene flow was found between both sub-regions. Virulence test were conducted on nine Argentinean and 14 foreign wheat cultivars with some level of resistance to the pathogen with 16 genetically different isolates selected from the previous work, in two environments in seedlings and adult stage. Cultivars with good levels of partial and complete resistance to some isolates were detected. Populations with some of these materials are been developed to identify genes in Argentinean wheat cultivars. Our work have also mapped a resistance locus on the centromeric region of chromosome arm 7 DS of a Synthetic 6 x at the seedlings and adult stage. On the basis of its relationship with the microsatellite marker Xgwm44, it is likely that the gene involved was Stb5, which proved to be effective against M. graminicola isolates originating from both Europe and South America. In addition, a source of resistance has been mapped on chromosome 7D of spelt wheat, Triticum aestivum L. subsp. spelta (L.) Thell. Two regions of the chromosome were associated with isolate-specific QTL expressed one at the seedling and another at the adult plant stage. The seedling resistance locus QStb.ipk-7D1 was found in the centromeric region of chromosome 7D, which corresponds to the location of the major resistance gene Stb4 originated from bread wheat cultivar ?Tadinia? and Stb5 originated from Triticum tauschii . The adult resistance locus QStb.ipk-7D2 was found on 7DS in a similar position to the locus Lr34/Yr18 known to be effective against multiple pathogens. Furthermore, using a mapping population of the ITMI (W7984 x Opata 85), three loci were discovered on the short arms of chromosomes 1D, 2D and 6B at the seedling stage, and two loci-specific QTL were found on the long arms of chromosomes 3D and 7B at the adult stage.