In Vitro Evaluation Of Selected Plant Extracts As Biocontrol Agents Against Black Mold (Aspergillus Niger Van Tieghem) Of Onion Bulbs (Allium Cepa L.)

Black mold disease caused by Aspergillus niger V. Tiegh. is the most devastating infection occurs in onions (Allium cepa L.) under field and store conditions. The use of biocontrol agents is ecofriendly approach for controlling seedborne and soilborne diseases compared to the use of toxic synthetic fungicides. This study has been designed to assess the contamination levels of onion seeds with A. niger and its effect on seed germination, and to evaluate the in vitro antifungal activity of Prunus mahaleb seeds, Commiphora myrrha resin (0.5, 1.0, 1.5, 2.0 g/100 ml), Syzygium aromaticum dry buds (clove), and Panax ginseng roots extracts (0.5, 1.0, 2.0, 2.5 g/100 ml) against black mold of onion bulbs. The fungus is seedborne pathogen which significantly contaminated onion seeds (89-100%) and reduced seed germination (39-83%). The extracts of clove caused 43-96% inhibition in spore germination followed by mahaleb (37-96%), myrrha (33-88%), and ginseng (34-87%). The highest concentration of these extracts (3.0%) did not affect seed germination, but significantly reduced seed contamination by A. niger up to 84%, 80%, 71%, and 65% for Syzygium aromaticum, Syzygium aromaticum, Panax ginseng and Prunus mahaleb, respectively. The extracts apparently inhibited the fungal growth and mold development on stored onion bulbs which indicates the antifungal property of these extracts against A. niger. Therefore, they can be recommended as effective biocontrol agents to reduce seed contamination and enhance the storability of onion bulbs. Thus, the use of healthy and certified seeds for onion production is a priority.