256 CONTROL OF SOIL-BORNE PLANT DISEASES 



flora could even be directed against internal seed infection, since appre- 

 ciable damage to surface-sterilized flax seed was found to occur in steri- 

 lized but not in unsterilized soil. 



CONTROL OF PATHOGENIC FUNGI IN SOIL BY 



INOCULATION WITH ANTAGONISTIC 



MICROORGANISMS 



Despite the favorable results obtained from the action, in artificial 

 culture, of antagonistic bacteria and fungi upon plant pathogens, the 

 field results have often been rather disappointing. The soil microflora 

 seems to have no marked effect on certain diseases, such as the seedling- 

 blight of barley j the antagonistic action of the soil population appears 

 (127) to be insufficient to suppress the injury caused by diseased seed. 

 The addition of T. Ugnorum and certain other fungi and bacteria to in- 

 fected seed or to sterilized soil inoculated with H. sativum often pre- 

 vented seedling injury, increased the stand, and decreased the number 

 of deformed seed. Chudiakov ( 130) suggested inoculation of seed with 

 bacteria, for the control of flax against infection with Fusarium. It has 

 been said that wheat seedlings were protected from attack by the simul- 

 taneous introduction of lytic bacteria with the pathogenic fungus, but 

 when the bacteria were introduced 24 hours after the fungus, they were 

 unable to protect the wheat sown 3 days later. 



On the basis of extensive studies on the control of plant-disease-pro- 

 ducing fungi by means of antagonistic soil microorganisms, Novogrud- 

 sky (646) came to the following conclusions: The distribution and 

 vigor of parasitic fungi are a result, on the one hand, of resistance and 

 immunity of plants to infection, and, on the other, of the antagonism 

 between soil microorganisms and pathogenic fungi. Among the numer- 

 ous forms of antagonism existing between soil microorganisms and 

 pathogens, those bacteria which produce lysis of fungi deserve particu- 

 lar attention. The bacteria are widely distributed in nature j they are 

 able to destroy and to dissolve the mycelium and the spores of different 

 fungi, including species of Fusarium, Colletotrichum, and other phyto- 

 pathogenic fungi. The lytic effect takes place not only in artificial me- 

 dia, but also in the soil. The inoculation of sterilized soil with F. grami- 



