Abstract

                                Attempts have been made by several workers to make use of the phenomenon of antibiosis in plant disease control. In 1912 Fawcett found that canker lesions were not produced when walnut branches were simultaneously inoculated with Pseudomonas Juglandis and Dothiorella gregaria. Hartley in 1921 found that the inoculation of steamed soil with some soil saprophytes resulted in a decrease of the parasitic activity of Pythium debaryanum on conifer seedlings. In 1924 Porter found that the incidence of diseases of wheat and flax caused by Helminthosporium sativum, and Fusarium lini was much reduced by the antagonistic activity of a bacterium. Machacek in 1928 reported that Penicillium expansum and a species of Cladosporium completely inhibited the growth of Sclerotinia fructicola and Botrytis sp., respectively. Sanford and Broadfoot, in 1931, reported that the take-all' disease of wheat could be controlled by the activities of some soil inhabiting fungi, bacteria and actinomycetes. In the same year Henry found that soil bacteria and fungi could control the foot-rot problem of wheat caused by H. sativum and F. culmorum in sterilized soil. Weindling, in 1932-34, demonstrated that Trichoderma lignorum markedly reduced the parasitic activity of Rhizoctonia solani and Phytophthora parasitica on citrus seedlings. Subsequently Carter, Allen and Haenseler, Weindling and Fawcett, Garett, Millard and Taylor and other workers proved beyond doubt the beneficial effects of saprophytic bacteria and fungi on plant pathogens and the possibilities of using them for controlling diseases.

Key words :