The phytopathogenic basidiomycetous fungus, Rhizoctonia solani, has a wide range of host plants including members of the family Poaceae, causing damping-off and root rot diseases. In this study, we biosynthesized spherical-shaped silicon dioxide nanoparticles (SiO₂ NPs; sized between 9.92 and 19.8 nm) using saffron extract and introduced them as a potential alternative therapeutic solution to protect wheat seedlings against R. solani. SiO₂ NPs showed strong dose-dependent fungistatic activity on R. solani, and significantly reduced mycelial radial growth (up to 100% growth reduction), mycelium fresh and dry weight, and pre-, post-emergence damping-off, and root rot severities. Moreover, the impact of SiO₂ NPs on the growth of wheat seedlings and their potential mechanism (s) for disease suppression was deciphered. SiO₂ NPs application also improved the germination, vegetative growth, and vigor indexes of infected wheat seedlings which indicates no phytotoxicity on treated wheat seedlings. Moreover, SiO₂ NPs enhanced the content of the photosynthetic pigments (chlorophylls and carotenoids), induced the accumulation of defense-related compounds (particularly salicylic acid), and alleviated the oxidative stress via stimulation of both enzymatic (POD, SOD, APX, CAT, and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machinery. Collectively, our findings demonstrated the potential therapeutic role of SiO₂ NPs against R. solani infection via the simultaneous activation of a multilayered defense system to suppress the pathogen, neutralize the destructive effect of ROS, lipid peroxidation, and methylglyoxal, and maintain their homeostasis within R. solani-infected plants.

The genus Aspergillus comprises several species that play pivotal roles in agriculture. Herein, we morphologically and physiologically characterized four genetically distinct Aspergillus spp., namely A. japonicus, A. niger, A. flavus, and A. pseudoelegans, and examined their ability to suppress the white mold disease of bean caused by Sclerotinia sclerotiorum in vitro and under greenhouse conditions. Seriation type of Aspergillus spp. correlates with conidiospores discharge as detected on the Petri glass lid. Members of Nigri section cover their conidial heads with hard shells after prolonged incubation. In addition, sporulation of the tested Aspergillus isolates is temperature sensitive as it becomes inhibited at low temperatures and the colonies become white. Examined Aspergillus spp. were neither infectious to legumes nor aflatoxigenic as confirmed by HPLC except for A. flavus and A. pseudoelegans which, secreted 5 and 1 ppm of aflatoxin B1, respectively. Co-inoculations of Sclerotinia’s mycelium or sclerotia with a spore suspension of Aspergillus spp. inhibited their germination on PDA at 18 °C and 28 °C, and halted disease onset on detached common bean and soybean leaves. Similarly, plants treated with A. japonicus and A. niger showed the highest survival rates compared to untreated plants. In conclusion, black Aspergillus spp. are efficient biocides and safe alternatives for the management of plant diseases, particularly in organic farms.

Powdery mildew, caused by Blumeria graminis (DC.) Speer f. sp. tritici (Em. Marchal), is a serious disease of wheat that can cause a large reduction in yield. In Egypt, high powdery mildew severity has been observed in the past few years on many commercial cultivars of both bread and durum wheat. Little information is available about virulence characteristics of the Egyptian B. graminis f. sp. tritici population in Egypt or the resistance of Egyptian wheat cultivars to powdery mildew. Virulence frequencies of a representative sample of the Egyptian B. graminis f. sp. tritici population were studied. Seven provinces were chosen to represent the country: two in Upper Egypt (Qena and Sohag), one in Middle Egypt (El Minia), and four in the north (Alexandria, Kafr Elsheikh, Dakahlia, and Sharqia). Ten isolates from each province (70 isolates total) were derived from single ascospores and used for this study. They were inoculated individually on 21 powdery mildew differential lines, each bearing a single resistance (Pm) gene. Also, the responses of 14 Egyptian bread wheat cultivars and 6 durum cultivars to each of the 70 isolates were evaluated individually. Among all tested Pm genes, only seven (Pm1b, Pm2, Pm21, Pm34, Pm36, Pm37, and Pm53) were effective against B. graminis f. sp. tritici isolates from all provinces. Several other genes were effective against most or all isolates from a majority of provinces. All tested bread wheat cultivars showed full susceptibility to all isolates, whereas two durum wheat cultivars, Beni-Suef-5 and Beni-Suef-6, had intermediate responses to a large percentage of the isolates, likely indicating partial resistance. To enhance mildew resistance in Egyptian wheat cultivars, it is recommended to use combinations of genes that are nationally effective or effective against multiple provincial B. graminis f. sp. tritici populations.

The in vitro and in vivo efficacy of three biocontrol agents, Trichoderma viride, Pseudomonas fluorescence, and Bacillus subtilis, were tested against Rhizoctonia solani (AG-4) infection compared to two conventional fungicides (Rizolex-T 50%wettable powder and Amistar 25%). Antifungal enzyme activity was assayed in the culture filtrate of the biocontrol agents. The impact of the tested biocontrol agents on the induction of the coriander immune system was investigated against R. solani by assessing the resistance-related enzymes and compounds in biocontrol agent-treated plants compared with the control. The obtained results revealed that all tested biocontrol agents significantly reduced the linear growth of R. solani, and T. viride recorded the highest inhibition percentage. This could be linked to the ability of T. viride to produce higher activities of antimicrobial enzymes, i.e., cellulase, chitinase, and protease, compared to P. fluorescence and B. subtilis. Applying the tested biocontrol agents significantly alleviated pre- and post-emergence damping-off and root rot/wilt diseases of infected coriander compared with untreated plants. The tested biocontrol agents exhibited significantly higher germination percentage and vigor index of the coriander than the tested fungicides. The tested biocontrol agents significantly minimized the reduction of photosynthetic pigments induced by R. solani. In addition, the results showed a significant increase in enzymes/molecules (i.e., phenylalanine, catalase, peroxidase, catalase, superoxide dismutase, phenylalanine ammonia-lyase, phenolics, ascorbic acids, and salicylic acid) involved directly and indirectly in coriander resistance to R. solani. The principal component analysis of the recorded data recommended the role of the high accumulation of oxidative parameters (hydrogen peroxide and lipid peroxidation) and the inhibition of phenolic compounds in the downregulation of coriander resistance against R. solani. The heatmap analysis results revealed that biocontrol agents, especially Trichoderma, enhanced the resistance against R. solani via the stimulation of salicylic acid, phenolics, and antioxidant enzymes. Overall, the data recommended the efficacy of biocontrol agents, especially T. viride, against R. solani infecting coriander plants, which could be an efficient and a safer alternative to conventional fungicides.

Increasing ambient ozone (O₃) concentrations and resurgent rust diseases are two concomitant limiting factors to wheat production worldwide. Breeding resilient wheat cultivars bearing rust resistance and O₃ tolerance while maintaining high yield is critical for global food security. This study aims at identifying ozone tolerance among key rust-susceptible wheat genotypes [Rust near-universal susceptible genotypes (RnUS)], as a first step towards achieving this goal. Tested RnUS included seven bread wheat genotypes (Chinese Spring, Line E, Little Club, LMPG 6, McNair 701, Morocco and Thatcher), and one durum wheat line (Rusty). Plants were treated with five O₃ concentrations (CF, 50, 70, 90, and 110 ppb), in two O₃ exposure systems [continuous stirred tank reactors (CSTR) and outdoor-plant environment chambers (OPEC)], at 21–23 Zadoks decimal growth stage. Visible injury and biomass accumulation rate were used to assess O₃ responses. Visible injury data showed consistent order of genotype sensitivity (Thatcher, LMPG 6 > McNair 701, Rusty > Line E, Morocco, Little Club > Chinese Spring). Additionally, leaves at different orders showed differential O₃ responses. Biomass accumulation under O₃ stress showed similar results for the bread wheat genotypes. However, the durum wheat line “Rusty” had the most O₃-sensitive biomass production, providing a contrasting O₃ response to the tolerance reported in durum wheat. Chinese Spring was the most tolerant genotype based on both parameters and could be used as a source for O₃ tolerance, while sensitive genotypes could be used as sensitive parents in mapping O₃ tolerance in bread wheat. The suitability of visible symptoms and biomass responses in high-throughput screening of wheat for O₃ tolerance was discussed. The results presented in this research could assist in developing future approaches to accelerate breeding wheat for O₃ tolerance using existing breeding materials.