Characterization of strigolactones produced by Orobanche foetida and Orobanche crenata resistant faba bean (Vicia faba L.) genotypes and effects of phosphorous, nitrogen, and potassium deficiencies on strigolactone production

• Impaired strigolactones production is involved in the resistance to Orobanche foetida and O. crenata on faba bean genotypes.
• Three strigolactones were detected from faba bean roots: Orobanchol, Orobanchyl acetate and unidentified strigolactones.
• Nitrogen (N) and phosphorous (P) but not potassium (K) fertilization, are effective to reduce Orobanche spp. infestation.

In the present study, characterization of strigolactones (SLs) produced by some Tunisian faba bean genotypes partially resistant to Orobanche foetida Poir. and O. crenata Forsk. was conducted by LC–MS/MS and the results were compared with that of a susceptible genotype. Among the eight partially resistant genotypes grown hydroponically, only the genotype G5 and the susceptible one G9 (Badï) exuded into growth media similar mixture of three SLs, orobanchol, orobanchyl acetate, and a novel SL at amounts detectable by LC–MS/MS. This implies that, for the resistant genotypes except for G5, impaired SL production confers resistance to Orobanche. The amounts of orobanchol and orobanchyl acetate exuded by G5 and G9 were quantified by LC–MS/MS. Results showed that the susceptible genotype G9 produced larger amount of orobanchol than did the resistant genotype G5, and in both genotypes the amounts of orobanchol were significantly higher than that of orobanchyl acetate. Other mechanisms, acting after induction of Orobanche seeds germination, could be implied in the resistance of genotype G5. Since nutrient availabilities have been shown to affect SL production, effects of N, P and K deficiencies on SL production were studied for genotypes G5 and G9. Both N and P deficiencies enhanced SL exudation in both genotypes, while K deficiency did not affect it.