Essential oils (EOs) are the volatile lipophilic components extracted from plants. Many EOs have demonstrated strong antimicrobial properties when tested in in vitro experiments. The commercial applications of these EOs require a suitable formulation constituted by biodegradable compounds that protect them from degradation and evaporation at the same time that allows for a sustained release. The objective of this study was therefore to reduce the rate of evaporation of the oil via microencapsulation. Alginate microspheres (AMSs) were prepared using emulsion extrusion method. The AMSs were hardened with a cross-linking agent, calcium chloride. The effects of the three variables: alginate concentration (0.5%-8%), the amount of cross-linking agent (0.125%-2%) and time of cross-linking (5-30 min.) on loading capacity and encapsulation efficiency (EE, %) were studied. The effect of the amount of cross-linker was significant on loading capacity (%) and EE (%). The AMSs under the optimized conditions provided loading capacity of 22%-24% and EE of 90%-94% based on type of EO. The antifungal activity of vapors of microencapsulated and non-microencapsulated oils were evaluated against two of pathogenic fungi species for stored grains: Aspergillus niger and Fusarium verticillioides. The optimized MSs were observed to have a sustained in vitro release profile (50% of the antifungal activity was maintained at the 8th day of the study). In conclusion, encapsulation in Ca-alginate microspheres may effectively reduce the evaporation rate of essential oils, thus increase the potential antifungal activity.

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Rhizoctonia solani causes severe diseases in many plant species, particularly root rot in tomato plants. For the first time, Trichoderma pubescens effectively controls R. solani in vitro and in vivo. R. solani strain R11 was identified using the ITS region (OP456527); meanwhile, T. pubescens strain Tp21 was characterized by the ITS region (OP456528) and two genes (tef-1 and rpb2). The antagonistic dual culture method revealed that T. pubescens had a high activity of 76.93% in vitro. A substantial increase in root length, plant height, shoot fresh and dry, and root fresh and dry weight was indicated after applying T. pubescens to tomato plants in vivo. Additionally, it significantly increased the chlorophyll content and total phenolic compounds. The treatment with T. pubescens exhibited a low disease index (DI, 16.00%) without significant differences with Uniform® fungicide at a concentration of 1 ppm (14.67%), while the R. solani-infected plants showed a DI of 78.67%. At 15 days after inoculation, promising increases in the relative expression levels of three defense-related genes (PAL, CHS, and HQT) were observed in all T. pubescens treated plants compared with the non-treated plants. Plants treated with T. pubescens alone showed the highest expression value, with relative transcriptional levels of PAL, CHS, and HQT that were 2.72-, 4.44-, and 3.72-fold higher in comparison with control plants, respectively. The two treatments of T. pubescens exhibited increasing antioxidant enzyme production (POX, SOD, PPO, and CAT), while high MDA and H2O2 levels were observed in the infected plants. The HPLC results of the leaf extract showed a fluctuation in polyphenolic compound content. T. pubescens application alone or for treating plant pathogen infection showed elevated phenolic acids such as chlorogenic and coumaric acids. Therefore, the ability of T. pubescens to inhibit the growth of R. solani, enhance the development of tomato plants, and induce systemic resistance supports the application of T. pubescens as a potential bioagent for managing root rot disease and productivity increase of crops.

In this study, the potential of some bio-agents, fluopyram and fosthiazate were investigated against rootknot nematodes (Meloidogyne spp.) on guava trees under field conditions for two successive seasons (2020 & 2021). The examined bio-agents were; Bio-Nematon ® (Paecilomyces lilacinus), Bio Cure-F ® (Trichoderma viridi), Bio Cure-B ® (Pseudomonas fluorescens) and BIOTECT ® (Bacillus thuringiensis var. kurstaki). The infection parameters of root-knot nematodes (Meloidogyne spp.) were recorded at 35 and 70 days after treatment. Resultsindicated that all the applied treatments suppressed the soil population density (J2/250g soil) at range of 68.75 to 88.85% during the 1 st season, and from 57.72 to 92.92% during the 2 nd season. Besides, the numbers of root galls were decreased at range of 60.22 to 77.11% and from 57.90 to 70.90% during 1 st and 2 nd seasons, respectively. Also, the number of isolated eggs from roots was decreased at range of 67.13 to 94.61% and from 51.37 to 88.45% during 1 st and 2 nd seasons, respectively. However, the content of total N, P and K (%) in leaves of guava trees was fluctuated during both seasons.