Effect of Fusarium and Rhizoctonia isolates on the pre-attachment stage of Phelipanche aegyptiaca

Phelipanche aegyptiaca is an obligate root-parasitic plant of the Orobanchaceae family that comprises the most threatening weed for major crops in regions with a Mediterranean climate zone, as well as in Asia, southern and Eastern Europe. The pre-attachment stage is crucial for its successful attachment and parasitism, making this phase a key target for biological control strategies. In this study, the effect of 79 fungal isolates, including 49 Fusarium and 30 Rhizoctonia, on the pre-attachment stages of P. aegyptiaca were investigated. According to the experimental results, the Fusarium isolates inhibited the seed germination by the rate of 17.9 to 97.1%, while the disease severity values were between 21.3 and 99.8%. Approximately 40% of the 49 Fusarium isolates exhibited high inhibition effects (70−100%) and around 70% of the isolates caused high disease severity (70−100%) on the radicle. A positive correlation was observed between the inhibition rate and disease severity for the Fusarium isolates. Moreover, 15 Fusarium isolates displayed high effects in both parameters simultaneously. In contrast, the Rhizoctonia isolates exhibited seed inhibition rates ranging from 1.2 to 37.6% and disease severity values between 0 and 66.0%, with none showing high effects on any pre-attachment stages. These findings suggest that the Fusarium isolates have a great potential to use biocontrol agents against P. aegyptiaca, while the Rhizoctonia isolates have less, which may be due to differences in their secondary metabolite profiles or other pathogenicity-related traits. These findings pave the way for future research to optimize Fusarium-based biocontrol strategies and better understand the broader potential of these fungal isolates in managing P. aegyptiaca.