Micronutrients play a prominent role in plant growth and development, and their bioavailability is a growing global concern. Zinc is one of the most important micronutrients in the plant life cycle, acting as a metallic cofactor for numerous biochemical reactions within plant cells. Zinc deficiency in plants leads to various physiological abnormalities, ultimately affecting nutritional quality and posing challenges to food security. Biofortification methods have been adopted by agronomists to increase Zn concentrations in crops through optimal foliar and soil applications. Changing climatic conditions and conventional agricultural practices alter edaphic factors, reducing zinc bioavailability in soils due to abrupt weather changes. Precision agriculture emphasizes need-based and site-specific technologies to address these nutritional deficiencies. Nanoscience, a multidimensional approach, reduces particle size to the nanometer (nm) scale to enhance their efficiency in precise amounts. Nanoscale forms of Zn⁺² and their broad applications across crops are gaining attention in agriculture under varied application methods. This review focuses on the significance of Zn oxide (ZnO) nanoparticles (ZnONPs) and their extensive application in crop production. We also discuss optimum dosage levels, ZnONPs synthesis, application methods, toxicity, and promising future strategies in this field.

Zinc (Zn), an important micronutrient, plays an essential role in plant growth and development. Being the most crucial divalent metallic enzyme, Zn acts as a catalyst in many biochemical processes that regulate growth hormones in plants. Nanoseed priming is an effective agrotechnology that enhances the quality parameters of young seedlings for establishing a good crop stand. In the present study, zinc nanoparticles synthesized from M. oleifera leaf extracts were characterized by UV spectroscopy, XRD, FTIR, FE-SEM, TEM, TGA, DLS, and zeta analysis. The synthesized nanoparticles showed moderate antioxidant, anti-inflammatory, and antimicrobial activities. Phytosynthesized nanoparticles were tested for their efficiency in modulating plant growth and development, where modern nanoscience technology is at the seedling stage. In the present research, tomato seeds were hydropriming carried out with sample solution of 100 mL from a 1 L stock solution for each treatment with ZnONPs at 50 ppm, 100 ppm, 150 ppm, 200 ppm, and 250 ppm, as well as ZnSO₄ used as an ionic control at 1.5 g/L. 150 and 200 ppm increased germination percentage. Plant height at seedling stage was enhanced to 22.33 and 19.67 cm at 150 and 250 ppm, respectively. Foliar applications were initiated at 35 DAT, when the plants were at 10–12 true leaves and in the transition phase of tomato plants from the vegetative stage to the flowering stage; 150 ppm induced early flowering, as well as the highest leaf area, TSS content, chlorophyll levels, the number of fruits per cluster, and the number of fruits per plant. Foliar application at 150 ppm enhanced the total and marketable yields to a maximum of 4102.63 and 3984.30 g, respectively. Foliar application at 150 ppm induced the lowest disease severity, at 20.02%, in vivo and in vitro, with the maximum mycelial inhibition of 19.50 mm at 0.15 mg/mL.

Leaf rust of wheat is an important biotic plant stress influence in yield reduction of wheat. Host resistance is a feasible approach for dealing with disease management in wheat. Germplasm screening with resistance reactions will be helpful in the development of resistant lines; on the other hand, plant cellular responses during the host pathogen interaction may vary depending on the resistance and susceptibility of the cultivar. Knowledge of cell membrane stability and stress protein during the pathogen interaction helps in quantifying disease and the effect of these parameters on yield losses. 48 germplasm has been screened with two susceptible germplasm, and two biochemical parameters such as proline and membrane stability were calculated among germplasm. Agra local and PBW343 show the lowest proline content at 0.505 and 0.405 μMoles/g, with the lowest membrane stability of 12.34 and 115.32 with susceptible reactions. Cluster analysis of the germplasm based on quantitative disease scoring and qualitative disease parameters divides the germplasm into four clusters, such as germplasm viz., cluster 1 with 16 germplasm viz., JSW 3, 5, 9, 8, 10, 11, 15, 16, 18, 19, 26, 28, 29, 32, 34, 41. This germplasm was observed with disease severity from 0.75 to 6, and the disease reaction of the germplasm ranges from R, RMR, and MR and was recorded as 1.85 to 2.475 μMoles/g, and EC or membrane stability was between 10.32 and 42. Observing the experimental studies, it was identified that the categorization of this germplasm into slow rust and race-specific based on the disease scoring and physio-biochemical parameters helps in the breeding of durable varieties.

Stripe rust or yellow rust caused by Puccinia striiformis f. sp. tritici of wheat is a major biotic stress with rapid epidemics. Host-plant resistance is one of major breeding strategies in development of resistant cultivars, wheat germplasm showing great genetic diversity for resistance was screened for identifying potential resources for major and minor resistance genes. Forty-seven germplasms of advanced breeding materials were selected and seedling reaction test was conducted on germplasm to know potential race specific resistance against Pst stripe rust races. Relative susceptibility index assessed based on seedling infection type and their numerical response values. Adult plant screening under natural epiphytotic conditions recorded different quantitative disease parameter values viz., area under the disease progress curve (AUDPC), average coefficient of infection (ACI) and relative resistance index (RRI) which helps in categorising germplasm into durable non-specific ones. The phenotypic assessment of germplasm which was categorised as resistant germplasm, was validated through simple sequence repeat (SSR) markers for Yr race specific genes such as Yr5, YR10 and Yr15 using different SSR markers viz., Xgmw501, Brac349, Xpsp300, Xgmw273 and Gms413. The gene Yr5 was postulated in 14 germplasm lines, Yr15 in 14 germplasm lines and Yr10 in 11 germplasm lines. Four germplasm postulated with Yr5+Yr15, six germplasm postulated with Yr15+Yr10 and Yr5+Yr10 postulated in three germplasm and two germplasm showed immune response with other race specific resistance.