All olive (Olea europaea L.) plant tissues have a high phenolic content. However, the effects of the cultivar and sampling period on the tissue phenolic content remain almost unknown; in addition, the interactions between nutrient uptake and leaf phenol concentrations have not been clarified. This study sampled olive leaves to explore how the cultivar, sampling period, and their interaction affect leaf phenol and nutrient concentrations. Leaves were collected from six cultivars during three seasonal periods: harvest (October; SP1), dormancy (January; SP2), and pruning (March; SP3). Five were Istrian cultivars (‘Bova’, ‘Buža muška’, ‘Buža puntoža’, ‘Istarska bjelica’, ‘Rošinjola’), and one was the Italian cultivar ‘Leccino’. Phenolic profiles in olive leaves were correlated with potassium (K), phosphorus (P), and copper (Cu) concentrations. However, significant correlations between these nutrients and oleuropein, verbascoside, and total phenolic content (TPC) were determined only for ‘Rošinjola’. Oleuropein was the most abundant phenolic compound, while among genotypes, ‘Buža muška’ showed the highest oleuropein levels across all sampling periods, indicating its potential source of oleuropein in olive leaves. Seasonal variations in olive leaf phenolic compounds appear to be strongly influenced by phenological phase, nutrient dynamics, and weather conditions, as confirmed by multivariate analysis across sampling periods and cultivars. The findings emphasise the importance of selecting both an appropriate cultivar and sampling period to maximise the accumulation of olive leaf phenolic compounds. Nevertheless, long-term experimentation on cultivars with a high leaf phenolic potential, like ‘Buža muška’ and ‘Rošinjola’, is necessary in order to develop appropriate farming strategies for maximising phenolic compounds with human or plant health benefits.

In April 2015, dieback of young olive trees (Olea europaea L., cultivars Istarska bjelica and Buza) occurred in a private orchard near Vodnjan in Istria, Croatia. From total of 50 trees, 8 (16 %) showed symptoms of dieback, with branches that had vascular browning in cross section and attached light brown, downwardly curled leaves. A fungus, was consistently isolated from surface sterilized wood pieces of diseased branches, obtained in pure cultures on potato dextrose agar (PDA) by monohyphal isolation, and incubated at 25°C in darkness. Colonies grew slowly (1.9 mm/day), and the initial white color became gradually dark. Microscopic analysis showed hyaline, septate hypha with conidiophores bearing phialides in verticillate arrangement producing hyaline, single-celled, ovoid to ellipsoid conidia, 4.8 ± 0.7 µm x 2.4 ± 0.4 µm (n = 100). Dark parts of the colonies showed abundant dark-brown microsclerotia embedded in PDA. Solitary microsclerotia (rounded, elongated or irregular in shape) and their aggregates...

Fungal infections caused by Fusarium solani demand sustainable alternatives to conventional fungicides and free nanoparticles, which often show poor stability and rapid release. This study developed zinc-crosslinked alginate microparticles containing silver (AgNPs), zinc oxide (ZnONPs), or both to improve nanoparticle stability, sustain release, and enhance antifungal efficacy. Microparticles were produced by ionic gelation and characterized by FTIR, microscopy, swelling analysis, encapsulation efficiency, and kinetic modeling. AgNPs weakened hydrogen bonding within alginate, yielding rough, porous structures, whereas ZnONPs strengthened COO⁻–Zn²⁺ interactions, forming smoother surfaces with smaller pores; co-loaded particles combined both characteristics. Encapsulation efficiencies were 77.9% (AgNPs) and 98.6% (ZnONPs), with co-loaded systems retaining 64.0% and 98.9%, respectively. Swelling was highest in AgNP-loaded microparticles (63.8%) and lowest in ZnONP and co-loaded systems (≈42%). AgNPs followed anomalous transport (n = 0.65), while ZnONPs transitioned from Fickian diffusion (n ≈ 0.36–0.38) to zero-order release (K₀ = 1.00 for ZnONPs alone; 0.80 co-loaded). Antifungal tests showed strong inhibition: 80.7% for AgNPs, 91.4% for ZnONPs, and 99.7% for co-loaded formulations. Microscopy confirmed membrane disruption, hyphal collapse, and ROS-mediated damage, with the strongest effects in co-loaded samples. These results demonstrate a tunable, synergistic, sustained-release platform that outperforms single nanoparticles and offers a promising strategy for sustainable crop protection.

Olive leaf biomass, generated as a residue of olive cultivation, represents a readily available source of phenolic compounds with recognized nutraceutical potential. However, the composition of these bioactive compounds is influenced by both genetic and environmental factors. Therefore, this study aimed to evaluate the effects of cultivar and sampling period on the biophenolic composition and mineral nutrient content of olive leaves from six cultivars maintained under comparable environmental conditions in central Dalmatia, Croatia. Leaves were collected during the harvest and pruning periods. Phenolic compounds were determined by HPLC and mineral nutrients by ICP-MS, FAAS, and UV/Vis spectrophotometry. Significant cultivar-dependent differences were observed for most analyzed phenolic compounds and mineral nutrients. Cultivar ‘Leccino’ exhibited the highest concentrations of several phenolic compounds and total phenols during the pruning period, while distinct accumulation patterns were recorded among cultivars. Ten of the thirteen individual phenolic compounds showed a significant sampling-period effect; nine were higher during the pruning period, whereas apigenin was higher at harvest. Seven of the ten mineral nutrients were significantly affected by sampling period, all of them decreasing towards pruning. Multivariate analysis identified cultivar as the dominant source of variation in both fractions, and the phenolic and mineral profiles were congruent among cultivars within each sampling period. Higher phenolic accumulation during the pruning period differed in magnitude among cultivars for 15 of the 24 variables. These findings support the potential valorization of olive leaves as a source of bioactive compounds and highlight cultivar and sampling period as important considerations for their targeted utilization.