Agrobacterium Radiobacter Strain 84 and Biological Control of Crown Gall

Abstract

Crown gall caused by Agrobaeterium tume/adens is of particular economic concern to nurseries growing rosaceous plants, Rubus species, grapevines, and various nut-bearing trees. Epidemics of 80-100% galled nursery stock have occurred in the Pacific Northwest, but they are usually sporadic and infrequent. Economic losses to nurseries occur primarily because most states prohibit interstate shipment or receipt of galled plants, which must then be destroyed. Losses are not confined to nurseries but can be severe in some orchards and landscape plantings. Since E. F. Smith's (57) demonstration that a bacterium was the causal agent of crown gall, there have been many studies on the host range of A. tume/adens, and major attempts have been made to control the disease with bactericides, which for the most part are ineffective. A novel approach to crown gall control was suggested in 1972 by Kerr (26) and colleagues (46). A nonpathogenic Agrobaeterium strain, A. radi­ obaeter strain 84, was inoculated onto peach seeds planted in soil infested with A. tume/adens. Three months later, 31 % of the plants from seeds inoculated with strain 84 were galled compared to 79% for the uninocu-