Non-chemical seed treatment in the control of seed-borne pathogens

Abstract

Non-chemical seed treatments include physical treatments, microbial treatments and treatments with other agents of natural origin like plant powders or extracts. Physical treatments with hot water, aerated steam, or dry heat have successfully been applied to a range of crops against a range of target pathogens and are in commercial use primarily for vegetable seeds. They can be very effective but need to be optimised on a per seed lot basis. Microbial seed treatments may control not only seed-borne pathogens but also provide some protection against pathogenic soil-borne inoculum. However, research on the use of micro-organisms as seed treatments has been limited, and there are only a few examples of commercial use. The latter is also true for botanical seed treatments, despite many reports of bactericidal and fungicidal effects of compounds from plants. The reason may be a lack of research on the one hand but mainly commercial constraints like development and registration costs in relation to market size. The current chapter gives an overview of approaches that have been taken to utilize the above-described non-chemical methods for control of important seed- borne pathogens of vegetables and small grain cereals. The examples treated include bacterial (black rot of brassicas, pea bacterial blight, bacterial blotch of cucurbits, black chaff of cereals), fungal (Alternaria diseases of carrot, black leg of brassicas, common bunt of wheat, Fusarium seedling diseases of small grain cereals, the loose smuts of barley and wheat, fungal diseases of rice and sorghum) and important viral diseases.