RAPD analyses have shown that two inter-fertile fungal species causing the Dutch elm disease (DED) (Ophiostoma ulmi and O. novo-ulmi) coexist in elm stands in Europe, together with their interspecies hybrids. This constitutes an opportunity for a rapid emergence of new pathogenic races via interspecific gene flow. However, due to the drawbacks of the RAPD technique, new molecular markers should be designed to investigate the evolution of the pathogen populations. This project will enable the fellow to acquire the needed knowledge on the genomics of DED fungi to develop new molecular markers, in order to analyse the evolution of the populations of these pathogens in European elm stands. In the partner organization (Laval University, Canada), the fellow will develop the new markers by a mining of Ophiostoma genomics data obtained at this Canadian University. At Laval University the research program will include: (i) screening Ophiostoma ESTs libraries for microsatellites and PCR-RFLP; (ii) designing PCR-markers for several polymorphic fitness/pathogenic genes; and (iii) developing PCR-markers to detect genome changes generate by transposition of transposable elements (TEs). In the return institution (Polytechnic University of Madrid, Spain) the fellow will study the populations of the pathogens, and the evolutionary mechanisms that might lead the pathogens to overcome the elm resistance of breeding programs. The study of the populations will comprise: (iv) the levels of sexual reproduction, hybridisation and introgression; (v) the genetic structure and gene flow among populations; and (vi) the analysis of the polymorphism generated by TEs in order to investigate whether their activation increases the genetic diversity of the pathogen populations. Two potential evolutionary scenarios will be investigated: populations of the DED pathogens in equilibrium (sensitive elm stands), and under selection (tolerant elm stands).
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