Efficacy of nanoparticles against purple blotch ( Alternaria porri ) of onion

Onion ( Allium cepa ), belonging to family, Amaryllidaceae is an essential crop in everyday life. However, its seeds are considered to be short lived due to its thin, shrunken and damaged seed coat, which makes it susceptible to fungal infection. An effort was made to enhance the seed quality of onion through management of seed borne disease, Purple Blotch of onion caused by Alternaria porri , though a novel method called Nano-priming. Experimentations were done to assess the antifungal activity of Zinc Oxide (ZnO) and Graphene Oxide (GO) nanoparticles (NPs) at different concentrations i.e., ZnO (25, 50, 100, 250 and 500 ppm) and GO (50, 100, 250, 500 and 1000 ppm) via mycelial reduction method and Agar well diffusion method. A ZnO @250 ppm significantly inhibited the in vitro growth of pathogen, as compared to Graphene oxide and the two positive controls-SAAF@ 0.1% a.i. (Carbendazim 12% + Mancozeb 63%) and Carbendazim (0.1% a.i.). Further, the seeds were artificially inoculated with spores of A. porri, followed by nano-priming of ZnO at different concentrations and evaluated for frequency of seed infection after 7 days. The results unveiled that ZnO NPs at concentration of 250 ppm and above inhibited the growth of test pathogen. Hence, the ZnO nano-priming at 250 ppm was found to be effective in enhancing the seed quality as well as protection against the Purple Blotch disease in onion .