How the plant immune system can drive the formation of n...(nnot be crossed at all anymore says Weig...)

While this view is widely accepted today, it is mostly unclear why such genetic barriers arise in the first place. Which advantage has the plant, when sometimes all seeds from a cross die" The current study offers a possible explanation. The plant genome changes under pressure from pathogens. Plant and pathogen are locked in a race, says Dangl, professor and expert in the genetics of plant pathology at the University of North Carolina. The pathogens tirelessly develop new strategies to attack the plant and evade its immune system. The plant, in turn, tries to prepare against as many new microbe weapons as possible. Armed to the teeth, it can happen that a harmless protein variant from a more distant relative is all of a sudden classified as dangerous and attacked.

The scientists are optimistic that their insights can be applied to other species. Common traits indicate that hybrid necrosis in crops such as wheat is caused by the same mechanisms as in thale cress. Dangl, therefore, believes that Arabidopsis can serve as a useful model for the understanding of hybrid necrosis in general. Such a model would be very useful for breeding, since such genetic incompatibilities prevents some of the crosses breeders would like to make, according to Dangl. The finding that only a few genes are responsible for each case of hybrid necrosis is particularly encouraging. It seems that only a few genetic changes are required to circumvent crossing barriers and to achieve a desired new combination of genetic traits. The flip side of the coin is that only minimal modifications in the genome can be sufficient to suppress the free exchange of genes between relatives, and that perhaps not much is needed to form a new species.