The possibility of inducing systemic resistance in roselle against root rot and wilt diseases was investigated using biotic and abiotic inducers. The biotic inducers included three biocontrol agents (i.e., Bacillus subtilis, Gliocladium catenulatum, and Trichoderma asperellum) and two biofertilizers (i.e., microbein and mycorrhizeen), while the abiotic inducers included three chemical materials (i.e., ascorbic acid, potassium silicate, and salicylic acid). In addition, preliminary in vitro studies were conducted to evaluate the inhibitory activity of the tested inducers on the growth of pathogenic fungi. The results show that G. catenulatum was the most efficient biocontrol agent. It reduced the linear growth of Fusarium solani, F. oxysporum, and Macrophomina phaseolina by 76.1, 73.4, and 73.2%, respectively, followed by B. subtilis by 71.4, 69, and 68.3%, respectively. Similarly, potassium silicate was the most effective chemical inducer followed by salicylic acid, each at 2000 ppm. They reduced the linear growth of F. solani by 62.3 and 55.7%; M. phaseolina by 60.7 and 53.1%; and F. oxysporum by 60.3 and 53%, respectively. In the greenhouse, all inducers applied as a seed treatment and/or foliar spray strongly limited the development of root rot and wilt diseases. In this regard, G. catenulatum, at 1 × 10⁹ CFU mL⁻¹, achieved the highest values of disease control, followed by B. subtilis; while T. asperellum, at 1 × 10⁵ CFU mL⁻¹, recorded the lowest values. In addition, the plants treated with potassium silicate followed by salicylic acid, each at 4 g/L, recorded the highest disease control compared to ascorbic acid at 1 g/L, which had the lowest values. The mixture of mycorrhizeen + microbein (at 10 g/kg seeds) was the most effective compared to either of them alone. All treatments, applied alone or in combination in the field, significantly reduced the incidence of diseases. The most effective treatments were a mixture of G. catenulatum (Gc) + Bacillus subtilis (Bs) + Trichoderma asperellum (Ta); a mixture of ascorbic acid (AA) + potassium silicate (PS) + and salicylic (SA); G. catenulatum; potassium silicate; and a mixture of mycorrhizeen + microbein. Rhizolix T had the highest disease-reducing efficacy. In response to the treatments, significant improvements in growth and yield, changes in biochemicals, and increased activities of defense enzymes were achieved. This research points to the activity of some biotic and abiotic inducers that can play a vital role in managing the root rot and wilt of roselle through the induction of systemic plant resistance.

Root rot and wilt diseases are among the most pressing obstacles to the production of rose flowers in Egypt. Isolation results showed that these diseases are mainly caused by seven soil-borne fungi. However, Fusarium roseum, Verticillium dahlia, and Rhizoctonia solani were the most pathogenic fungi against Rosa gallica and R. chinensis compared to other isolated fungi. The present study aimed to investigate the potential of some bio- and synthetic fertilizers, including seaweed extract, Rhizobacterin, NPK, and potassium silicate, as well as the chemical fungicide vitavax 200, to control root rot and wilt and improve growth and flowering traits of both R. gallica and R. chinensis. Under in vitro conditions, the highest linear growth inhibition of pathogenic fungi was achieved by seaweed extract followed by potassium silicate, at 400 ppm each. In addition, vitavax 200 at 400 ppm completely inhibited the linear growth of these fungi. The results also showed that all treatments applied in vivo significantly reduced the incidence of diseases on rose plants in both seasons, leading to an improvement in all growth and flowering parameters and an increase in the content of photosynthetic pigments, total carbohydrates, nitrogen, phosphorus, and potassium. In this regard, seaweed extract (4 and 2 g/L) and potassium silicate (4 g/L) were the most efficient, while Rhizobacterin (2 g/L) and NPK (2 g/plant) were the least effective. However, vitavax 200 was the most effective of all the treatments used. In conclusion, the results proved the possibility of increasing the tolerance of R. gallica and R. chinensis against root rot and wilt, while improving growth and flowering characteristics by using some bio- and synthetic fertilizers.

In vitro and in vivo studies were conducted to investigate the potential of four biocontrol agents (BCAs), namely Bacillus megaterium, Pseudomonas fluorescens, Trichoderma viride, and T. harzianum, individually and in combination with sodium nitrophenolate (SN) to control marigold powdery mildew. The results showed that all treatments led to a significant inhibition in the conidial germination of Golovinomyces cichoracearum in vitro. Maximum inhibition was recorded by T. harzianum (1×10⁹ CFU mL^-1) + SN (1.5%), followed by T. viride + SN, and B. megaterium + SN at the same concentrations as follows: 83.6, 79.1, and 70.6%, respectively. While the lowest inhibition (20.4%) was recorded by P. fluorescens (1×10⁵ CFU mL^-1). In the greenhouse, all treatments applied significantly reduced the disease severity and the area under the disease progress curve (AUDPC). The combination treatments had a better disease control response than individual treatments. Similar results were achieved in the field, where disease severity reduced to 9.2 and 10.3% in plants treated with T. harzianum + SN in the first and second seasons, respectively, compared to 40.2 and 44.1% in control in both seasons. Likewise, AUDPC reduced to 274 and 315 in plants treated with T. harzianum + SN in the first and second seasons, respectively, compared to 1207 and 1340 in control in both seasons. The treatments improved growth and productivity characteristics, as well as photosynthetic pigments, total phenolic compounds (TPC), and polyphenol oxidase (PPO) activity, while significantly reducing free proline (FP). In conclusion, BCAs applied individually or in combination with SN can be used effectively to suppress powdery mildew of marigold.

In the current study, thyme oil nanoemulsion was prepared for controlling of Sclerotinia sclerotiorum. Gas chromatography of thyme oil was performed and exhibited these bioactive components thymol, 1,8-cineole, α-terpinene and ρ-cymene as primary components. The nanoemulsion particles of thyme essential oil was evaluated using DLS. The results indicated that the PS after 30 min of sonication was about 36.65 nm, and Transmission electron microscopy analysis showed a spherical shape. Laboratory investigations showed that nanoemulsions at different concentrations (1000-5000 ppm) inhibited the growth of Sclerotinia sclerotiorum fungus. At a concentration of 3000 ppm, the nanoemulsion completely inhibited fungal growth. Treating fennel seeds with TEON, TEOE and TEOS had little effect on germination inhibition, with nanoemulsion being the most effective in promoting germination, while nanoemulsion was the best in terms of improving seed germination. As a result of nanoemulsion treatment, damping-off rates were significantly reduced, and plant growth was improved.