Physiological and phenotypic characters of sweet marjoram in response to pre-harvest application of hydrogen peroxide or chitosan nanoparticles

Abstract Hydrogen peroxide (H2O2) and Chitosan nanoparticles (CH NPs) represent a promising tool for improving the productivity and quality of marjoram herbs [Majorana hortensis, Moench.]. In this paper, we investigated the response of sweet marjoram to the foliar application of CH NPs and H2O2 during two successive seasons 2017 and 2018. Three concentrations of CH NPs, being “0.0325, 0.065 and 0.13 mM” and of H2O2 at 2.5, 5 and 10 mM as well as control were applied. Vegetative growth characters, total microbial load, essential oil (%) and its components were recorded. Whereas, fresh herbs of each treatment packaged and stored at 0 ± 5 °C and 90–95 % Relative Humidity (RH) for 21 days where the quality parameters were determined at weekly intervals of 7, 14 and 21 days. In 1st season, plants treated with H2O2 at 10 mM showed a pronounced increase in plant height, number of branches, fresh weight and oil % by 35 cm, 13 branches, 306.44 g/plant and 0.49 % respectively, compared to control of being 26.67 cm, 6.33 branches, 122.03 g/plant and 0.41 %, respectively. Additionally, the packed treated fresh herbs with 10 mM H2O2 presented the lowest value of weight loss (%), minimum decreased in total chlorophyll content and essential oil%, moreover, a significant minimum of both O2 % decreasing with CO2% increasing as compared to other treatments. Furthermore, the 2nd season had the same trend. This means, the pre-harvest H2O2 (10 mM) application have good potential strategy to improve the marjoram productivity with extend its shelf life period.