The current study focuses on the effects of Cucumber mosaic virus (CMV) infection on phytochemical changes and pathogenesis- and phenylpropanoid pathway-associated gene activities in squash (Cucurbita pepo L.) plants during a time course of 2 to 12 days post inoculation (dpi). The identity of the CMV isolate was confirmed by DAS-ELISA, TEM, and coat protein gene sequence. The CMV infection initially boosts and then suppresses transcript levels of the defense-related genes PR-1, PR-2, PAL, HQT, and CHS during the investigated time course compared to controls. The expression profile during the time-course study indicated that early, transient induction of PR-1 occurs during CMV infection, while CMV induced the expression of PR-2 in systemically infected squash tissues at all time points and suppressed the expression of PAL and HQT at 8-12 dpi. CHS transcript levels fluctuated between up- and down-regulation, but by 12 dpi, CHS expression reached its peak. The HPLC and GC–MS analyses of CMV-infected squash extracts revealed that different phenolic, flavonoid, and fatty acid compounds could be induced or suppressed upon CMV infection. In particular, CMV could suppress the synthesis of most phenolic compounds, specifically chlorogenic acid, possibly leading to the virus’s rapid spread.

The increasing usage of chemical control agents, as well as fungicides to manage plant diseases, causes human and environmental health problems. Macroalgae represent a reservoir for a tremendous variety of secondary metabolites that display a wide range of biological activities. However, their anti-phytopathogenic properties are still being studied. The current study was conducted to investigate whether or not the macroalgae Ulva fasciata extract exhibits antifungal and antiviral activities. In this regard, the organic extracts of U. fasciata were tested for their capabilities against tobacco mosaic virus (TMV) and three molecularly identified fungal isolates, Fusarium verticillioides, Alternaria tenuissima, and Botrytis cinerea with accession numbers OP363619, OP363620, and OP363621, respectively. Among the three tested extract concentrations, 100 µg/mL had the best biological activity against B. cinerea and TMV, with 69.26%and 81.25% inhibition rates, respectively. The HPLC analysis of chemical profiling of the extract showed the presence of a number of phenolic and flavonoid compounds widely known to display many biological activities. In this line, the 4-Hydroxybenzoic acid was the highest phenolic compound (12.3 µg/mL) present in the extract, followed by ferulic acid (9.05 µg/mL). The 7-hydroxyflavone (12.45 µg/mL) was the highest flavonoid in the organic extract of U. faciata followed by rutin, which recorded a concentration of 7.62 µg/ mL. The results of this study show that the U. fasciata extract has antiviral and antifungal properties, which makes it a possible source of natural antimicrobial agents.

The increasing use of chemical control agents and pesticides to prevent plant disease has resulted in several human and environmental health problems. Seaweeds, e.g., Amphiroa anceps extracts, have significant antimicrobial activities against different human pathogens. However, their anti-phytopathogenic activities are still being investigated. In the present investigation, three fungal isolates were isolated from root rot and grey mold symptomatic strawberry plants and were molecularly identified by ITS primers to Fusarium culmorum, Rhizoctonia solani, and Botrytis cinerea with accession numbers MN398396, MN398398, and MN398400, respectively. In addition, the organic extract of the red alga Amphiroa anceps was assessed for its antifungal activity against the three identified fungal isolates and tobacco mosaic virus (TMV) infection. At 100 µg/mL, the A. anceps extract had the best biological activity against R. solani, B. cinerea, and TMV infection, with inhibition rates of 66.67%, 40.61%, and 81.5%, respectively. Contrarily, the A. anceps extract exhibited lower activity against F. culmorum, causing inhibition in the fungal mycelia by only 4.4% at the same concentration. The extract’s HPLC analysis revealed the presence of numerous phenolic compounds, including ellagic acid and gallic acid, which had the highest concentrations of 19.05 and 18.36 µg/mL, respectively. In this line, the phytochemical analysis also showed the presence of flavonoids, with the highest concentration recorded for catechin at 12.45 µg/mL. The obtained results revealed for the first time the effect of the A. anceps extract against the plant fungal and viral pathogens, making the seaweed extract a promising source for natural antimicrobial agents.

Chemical pesticides and fungicides are used extensively, negatively affecting people’s health and the environment. Reducing synthetic pesticides and increasing the efficiency of sustainable food production using plant extracts as natural chemicals is a win–win. Here, we first describe and evaluate an ethanolic extract of Chorisia speciosa for its protective and curative activities against Rhizoctonia solani in greenhouse-grown tomato plants. The results showed that the mycelial growth of R. solani was completely suppressed in vitro by C. speciosa extract (10 µg/mL). Twenty days after fungal inoculation, the results demonstrated that using C. speciosa extract (10 µg/mL) in vivo significantly improved shoot and root growth parameters in protective and curative treatments. Further, the protective and curative treatments decreased the disease index by 26.67% and 53.33%, respectively. C. speciosa-treated tomato plants showed significantly increased antioxidant enzyme production (PPO, CAT, and SOD) and up-regulated PR-1, PR-2, PR-3, PAL, and CHS expression levels compared to untreated plants. According to HPLC examination, the most prevalent phenolic acids or flavonoid components quantities (µg/mL) noticed in C. speciosa extract were 7-OH-flavone (10.36), kaempferol (9.23), p-coumaric acid (8.65), ferulic acid (8.14), caffeic acid (7.59), gallic acid (6.33), and iso-ferulic (5.71). Our findings are the first to demonstrate that a C. speciosa extract can assist plants in combating fungal infestation. Therefore, the data imply that C. speciosa extract, as a natural and renewable product, could be adopted as a long-term approach for regulating plant fungus.