Mechanism of resistance in faba bean (Vicia faba) against broomrape species

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017.Broomrapes are weedy root parasitic plants that severely constraint faba bean (Vicia faba) production in Mediterranean basin. The most widely distributed species affecting faba bean is Orobanche crenata, although O. foetida and Phelipanche aegyptiaca are of local importance. Extensive and long efforts have been made by breeders, but unfortunately only moderately resistant cultivars are available to farmers. Here we summarize a series of experiments intending to characterize the resistance mechanisms involved in accessions with varying levels of resistance earlier reported. In a first rhyzotron experiment we studied the responses of six faba bean accession against O. crenata, O. foetida and P. aegyptiaca. A proportion of broomrape radicles successfully contacting faba bean roots might later become necrotic and fail the tubercle development against a Spanish O. crenata population. Formed broomrape tubercles might later become necrotic, mainly in the case of some of the resistant faba bean accessions to the Spanish O. crenata and to P. aegyptiaca but not to a Syrian O. crenata or to O. foetida. There was little effect on induction of seed germination. In an attempt to go deeper in the germination step a separate series of experiments was performed with other accessions allowing the identification of accessions inducing low germination of O. crenata, O. foetida and P. aegyptiaca, a mechanism that we consider most promising and we are combining with the other ones in our breeding program.N