Characterization of the Orobanche-Medicago truncatula association for studying early stages of the parasite-host interaction

There is an increasing interest in the legume species Medicago truncatula as a model plant for structural and functional genomic studies that can be used to identify agronomically important genes in legumes. Field screening has shown very high levels of resistance to Orobanche crenata in M. truncatula. However, in vitro studies with O. crenata, Orobanche foetida, Orobanche ramosa and Orobanche minor showed useful variation among accessions at early stages of the parasite-host interaction. Significant differences were observed in the levels of germination of O. crenata and O. foetida seeds induced by different accessions of M. truncatula. Only limited germination was observed on accession SA-4327. All accessions induced little O. ramosa and O. minor germination. Accessions also varied in the number of O. crenata and O. foetida attachments supported, with few developing on accession SA-27774. The variation observed for induction of germination and of subsequent attachment will be useful to isolating and characterizing genes involved in the early stages of Orobanche-host plant interaction and for the study of the biosynthetic pathways of production for germination stimulants.