A bioassay was developed to test for induction of systemic resistance in plants grown in various composts. Composts are blended into standard potting mixes and the mixes are seeded with radish. After one week, seedlings are inoculated with Xanthomonas campestris pv. Reductions in disease severity and pathogen population levels indicate induction of systemic resistance. Composts varied in their capacity to induce resistance in this system.
Infection can occur in both injured and uninjured roots, mostly in the feeder roots.
However, soil pH in commercial fields is apparently not related to disease incidence or severity. The findings reported here have practical implications for management of soilborne plant diseases in an ecologically sound, economically viable manner. Mycorrhizal inoculants have already been commercialized and the range of crops on which they can be used is expanding. Microbial antagonists, both bacterial and fungal, were identified and have the potential to reduce significantly disease losses. The importance of organic amendments in total management of soil microflora, including specific biocontrol agents, has been identified.