dr. MJW (Marieke) Jeuken

As a scientist and a lecturer, I am most motivated by genetic and evolutionary puzzles in plants, which relates from deviant segregations of traits in populations to evolutionay signatures in gene sequences.

During my BSc and MSc study of Biology at the University of Utrecht, I focused on genetics and did my MSc thesis work at the labs of Sjef Smeekens, Sjeng Horbach and Norman Terry (UC Berkeley).

My PhD graduation at the chair group Plant Breeding at WUR was under the supervision of Piet Stam and Pim Lindhout and concerned the exploration for resistance genes of a wild lettuce species (Lactuca saligna) against downy mildew disease in lettuce cultivation.

My current research focuses on the genetics behind biotic stress resistance, introgression issues and reproductive barriers between a crop and its wild relatives. In my model crop, lettuce (Lactuca sativa), I study the origin and mechanisms of resistance to downy mildew in a 'nonhost' species (L. saligna) and the nearly complete reproductive isolation between lettuce crop and this wild relative, L. saligna.

Within the discipline of biotic stress resistance, resistance in nonhost species is arguably the most interesting but least understood type of resistance. The wild species, L. saligna, is completely resistant to all downy mildew isolates and therefore it is considered a non-host species. As a rule, related host and non-host plant species are genetically too much diverged from each other and are not crossable or their F1 is completely sterile. Exceptionally, L. saligna is crossable with L. sativa  and the F1-hybrid is slightly fertile (2% seed set). These interspecific progenies offer a unique opportunity to study the resistance at the genetic level. The final aim is to unravel the genetic network of  this complete resistance against downy mildew and to introgress the resistant gene-variants in lettuce cultivars.

Furthermore, I use the same interspecific cross to study the adverse effects of this interspecific hybridisation. Plant hybrid incompatibilities, like hybrid inviability and sterility in F1 generation or derived progenies (like F2 or BC1), allow me to elucidate components of evolutionary diversification, reproductive barriers and speciation.

Both phenomena, reproductive isolation and resistance of nonhost species, are genetically complex traits. A good understanding of the causes and consequences of these complex traits is essential for insights in speciation and further application in plant breeding.

Picture: style (yellow), stigma (forked) and rows of fused anthers with pollen grains (dark pink) of a flower of lettuce