A reciprocal resistance system in two types of Barbarea vulgaris - An ecogenetic perspective.
Stina Christensen & Christine Heimes
dept. Agriculture and Ecology, Copenhagen University
Barbarea vulgaris (Brassicaceae) is a biennial or perennial herbal plant species, with a natural distribution in western Eurasia. In Denmark, the subspecies B.vulgaris ssp. arcuata occurs in two types, a hairy (Pubescent) P-type and a hairless (Glabrous) G-type. Populations of P- and G-type plants are found in all parts of Denmark, growing predominantly in separate patches. Hybrids between P- and G-type are rare, probably due to a partial reproductive barrier. The two plant types differ in morphological, cytological and chemical characters, and G-type plants are resistant to the flea beetle Phyllotreta nemorum, whereas P-type plants are susceptible. In contrast, G-type plants are susceptible to the oomycete pathogen Albugo candida, whereas P-type plants seem to be resistant.
Our talk will be based on the objectives of our PhD projects, aiming to entangle the role of resistance mechanisms in B. vulgaris from an ecological and genetic point of view:
- Is the geographical distribution of the two types caused by their belonging to two different evolutionary groups that occupied different refugia during the last ice age?
- Is the distribution of the P- and G-type populations in the landscape determined by different adaptations to local environmental conditions?
- Is resistance polymorphism in Danish B. vulgaris populations maintained by selection pressure exerted by the flea beetle P. nemorum and the oomycete A. candida?
- Is there a hybridization barrier and do hybrids have lower survival rates or lower fertility?
- Where in the genome does the Albugo-resistance map to, and what are the active defense compounds?
