Viruses pose a serious threat to the sustainable production of economically important crops around the world. In the past 20 years, potato virus Y (PVY) emerged as a relatively new and very serious problem in potatoes, even though it is the oldest known plant virus. Multiple strains of the virus cause various symptoms on the leaves and tubers of potatoes, resulting in yield reduction and poor-quality tubers. Consequently, it would be very interesting to learn what causes systemic PVY resistance in plants. Natural compounds such as chitosan (CHT) and phosphorus have been developed as alternatives to chemical pesticides to manage crop diseases in recent years. In the current study, potato leaves were foliar-sprayed with chitosan and phosphorus to assess their ability to induce PVY resistance. Compared to untreated plants, the findings demonstrated a significant decrease in disease severity and PVY accumulation in plants for which CHT and P were applied. Every treatment includes significantly increased growth parameters, chlorophyll content, photosynthetic characteristics, osmoprotectants (glycine betaine, proline, and soluble sugar), non-enzymatic antioxidants (glutathione, phenols, and ascorbic acid), enzymatic antioxidants (peroxidase, superoxide dismutase, lipoxygenase, glutathione reductase, catalase, β-1,3 glucanase, and ascorbate peroxidase), phytohormones (gibberellic acid, indole acetic acid, jasmonic acid, and salicylic acid), and mineral content (phosphorus, nitrogen, and potassium), compared to infected plants. However, compared to PVY infection values, CHT and P treatments showed a significant decrease in malondialdehyde, DPPH, H₂O₂, O₂, OH, and abscisic acid levels. In addition, increased expression levels of some regulatory defense genes, including superoxide dismutase (SOD), ascorbic acid peroxidase (APX), relative pathogenesis-related 1 basic (PR-1b), and relative phenylalanine ammonia-lyase (PAL), were found in all treated plants, compared to PVY-infected plants. Conclusion: Phosphorus is the most effective treatment for alleviating virus infections.

Salinity is linked to poor plant growth and a reduction in global food output. Therefore, there is an essential need for plant adaptation and mitigation of salinity stress conditions. Plants combat salinity stress influences by promoting a set of physiological, biochemical, and molecular actions. Tremendous mechanisms are being applied to induce plant stress tolerance, involving amino acid application. For evaluating the growth and productivity of Moringa oleifera trees grown under salt stress conditions, moringa has been cultivated under different levels of salinity and subjected to a foliar spray of proline (Pro) and phenylalanine (Phe) amino acids. Moringa plants positively responded to the lowest level of salinity as the leaves, inflorescences, seeds, and oil yields have been increased, but the growth and productivity slightly declined with increasing salinity levels after that. However, Pro and Phe applications significantly ameliorate these effects, particularly, Pro-treatments which decelerated chlorophyll and protein degradation and enhanced vitamin C, polyphenols, and antioxidant activity. A slight reduction in mineral content was observed under the high levels of salinity. Higher osmoprotectants (proline, protein, and total soluble sugars) content was given following Pro treatment in salted and unsalted plants. A significant reduction in oil yield was obtained as affected by salinity stress. Additionally, salinity exhibited a reduction in oleic acid (C18:1), linoleic (C18:2), and linolenic (C18:3) acids, and an increase in stearic (C18:0), palmitic (C16:0), eicosenoic (C20:2), and behenic (C22:0) acids. Generally, Pro and Phe treatments overcome the harmful effects of salinity in moringa trees by stimulating the osmoprotectants, polyphenols, and antioxidant activity, causing higher dry matter accumulation and better defense against salinity stress.

Prickly pear plant is widely cultivated in arid and semi-arid climates. Its fruits are rich in polyphenols, proteins, vitamin C, minerals, fatty acids, and amino acids. The oil extracted from the seeds also has a significant proportion of linoleic acid (ω6) and might be employed as a therapeutic raw material. The potential of enhancing fruit yield, increasing bioactive compounds of the fruit pulp, and improving the unsaturated fatty acid content of prickly pear oilseed by using the foliar application of brassinolide as a plant growth regulator was the main goal of this study. Prickly pear plants were foliar sprayed with a brassinolide solution at concentrations of 0, 1, 3, and 5 mg L⁻¹. The plant performance was significantly improved following brassinolide applications, as compared with untreated plants. The plants subjected to 5 mg L⁻¹ application exhibited 183 and 188% stimulation in the fruit yield, and 167 and 172% in the seed yield for the first and second seasons, respectively. The highest concentration of phenolic, flavonoid, protein, vitamin C, and maximum antioxidant activity in the fruit pulp was observed following 5 mg L⁻¹ brassinolide treatment. The oil yield has been increased by 366 and 353% following brassinolide at a 5 mg L⁻¹ level over control plants. Linoleic, oleic, and palmitic acids are the major components in prickly pear seed oil. Brassinolide foliar spraying induced an alternation in the fatty acid profile, as linoleic and oleic acids exhibited 5 and 4% higher following 5 mg L⁻¹ application as compared with untreated plants. In conclusion, the treatment of 5 mg L⁻¹ brassinolide improved the growth and quality of prickly pear plants by boosting fruit and seed yields, increasing active component content in the fruit pulp, improving mineral content, and increasing oil production and linoleic acid proportion.