Effect of biosynthesized nanoparticles on onion bulb production and shelf life of bulbs (Allium cepa L.)

Abstract

Biosynthesized nanoparticles are an emerging technology which improves crop production and its quality without affecting the environment. The zinc oxide nanoparticles (ZnO NPs) and silver nanoparticles (Ag NPs) were synthesized by biological method using leaf extract of Ocimum sanctum. The particles size was characterized by UV-Visible spectrophotometer and transmission electron microscope (TEM). The characteristic absorbance peak was observed at 385 and 450 nm for ZnO NPs and Ag NPs, respectively to confirm the synthesis of nanoparticles. The particle size of biosynthesized ZnO NPs and Ag NPs was 30-80 nm and 25-75 nm, respectively. The foliar application of biosynthesized ZnO NPs and Ag NPs was undertaken at 45, 60 and 75 days after transplanting of the seedlings @ ZnO NPs 50 ppm (S1), 75 ppm (S2), 100 ppm (S3), 150 ppm (S4) and Ag NPs @ 50 ppm (S5), 75 ppm (S6), 100 ppm (S7), 150 ppm (S8) along with untreated control (S9). The ZnO NPs @ 150 ppm (S4) was found superior for plant height (29.33, 59.20 and 60.00 cm at 30, 60 DAT and at harvest), number of leaves (3.87, 8.93 and 13.27 at 30, 60 DAT and at harvest), diameter of the bulb (0.88, 2.78 and 13.90 cm at 30, 60 DAT and at harvest), twin bulbs (2.73%), neck thickness (0.93 cm), bulb yield per plot (38.40 kg), bulb yield per ha (266.64 q) and marketable yield (97.44%). A remarkable result was also recorded in shelf life of onion bulbs. The treatment ZnO NPs @150 ppm (S4) was found minimum rotting losses (3.97, 4.02 and 2.68% at 30, 60 and 90 days after storage of bulbs), sprouting losses (1.99, 1.98 and 1.93% at 30, 60 and 90 DAS), total losses (5.96, 6.00 and 4.61% at 30, 60 and 90 DAS) and physiological loss in weight (3.80, 9.81 and 17.33% at 30, 60 and 90 DAS) during storage of bulbs than untreated control (S9).