Field and controlled conditions screenings of some faba bean (Vicia faba L.) genotypes for resistance to the parasitic plant Orobanche crenata Forsk. and investigation of involved resistance mechanisms
The parasitic weed Orobanche crenata is a serious constraint to legumes crops in Mediterranean area. In Morocco, heavy O. crenata infestation level was reported in many faba bean fields. Development of resistant faba bean genotypes remains a good long-term control strategy. So, identification of proper resistance sources remains a first step to attend this goal. In this perspective, six faba bean genotypes were subjected to field and controlled conditions (pot and Petri dishes experiments) evaluation for resistance/tolerance to Moroccan O. crenata. Root exudates and their implication on resistance/susceptibility to O. crenata were also investigated. Results showed a wide range of resistance but no complete resistance was detected. Thus, Giza 843, Misr1, and Misr3 genotypes showed good resistance level as compared to both susceptible genotypes Lobab and Aguadulce. Despite infection, the average yield of the three resistant genotypes was two to fourfold higher than the susceptible genotypes. Resistance of faba bean genotypes to O. crenata seems to occur at different levels of the parasite life cycle through: (1) developing lower host root density, (2) reduced attachment of O. crenata on host roots, and (3) delayed development of infection events on host roots. Furthermore, low induction of O. crenata seed germination could not be taken as an indicator of resistance. Based on low infection level and low impact of parasitism on yield and vegetative growth of host plants, Giza 843 was selected as a promising source of resistance to O. crenata which could be introduced into Moroccan faba bean breeding program.