Aims:To test the effect of zinc oxide nanoparticle (ZnO-NP) supplementation for enhancing the efficacy of Pseudomonas fluorescens NK4 siderophore as a biocontrol agent against P. viridiflava NK2 and a plant growth promoter.Methods and Results: Cucumber seedlings were treated with a suspension of P. fluorescens NK4 and its siderophore generated in siderophore-inducing medium (SIM), SIM supplemented with ZnO-NP (<100 nm) and SIM supplemented with Zn 2+ ions from Zn(NO 3 ) 2 . Supplementing SIM with ZnO-NP increased siderophore secretion in P. fluorescens NK4, and irrigation of cucumber seedlings with a filtrate containing the ZnO-NP-supplemented siderophore increased survival, improved vegetative and root growth, and thus increased yield similar to the effects of dipping seedlings in a P. fluorescens NK4 suspension. Both P. fluorescens NK4 and its ZnO-NP-supplemented siderophore inhibited P. viridiflava NK2 population growth in planta. Conclusions:The siderophore of P. fluorescens NK4 produced by ZnO-NP supplementation can be employed as a biocontrol agent and biofertilizer.Significance and Impact of the Study: ZnO-NPs can boost the synthesis of siderophores, which can then be employed as biofertilizers to boost iron bioavailability in iron-deficient soils.

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With the X. fastidiosa outbreak in Europe affecting olive and other major crops, the Jordanian Ministry of Agriculture (MoA) signaled a red warning light to prevent its entry into Jordan. An intensive survey was performed during 2016-2021 to assess its spread in Jordan across a range of agricultural crops in parallel to the previously published survey on olives. Grapevine (no. of samples: 899), stone fruit trees (1480), citrus fruit trees (1225), pome fruit trees (292), and ornamentals plants (1351) growing in Jordan were sampled. Both symptomatic and asymptomatic plants were sampled, in addition to collecting potential insect vectors from Hemiptera species. Plant samples were tested by ELISA (Enzyme-Linked Immunosorbent Assay) kits and their results were confirmed by conventional PCR (Polymerase Chain Reaction) using three sets of primers. Insect samples were tested using RST31/RST33 PCR. The obtained results did not show any confirmed positive results in any sample. These results indicate that X. fastidiosa has not been detected in Jordan despite a comprehensive survey. These results also demonstrate the importance of the monitoring and inspection programs executed by the MoA for detection of X. fastidiosa and identifying its potential insect vectors; these programs should be continued to prevent the entry of this bacterium and its potential insect vectors into Jordan from the neighboring countries.