Abstract of Dissertation Presented to the Graduate 

 Council of the University of Florida in Partial 

 Fulfillment of the Requirements for the 

 Degree of Doctor of Philosophy 



BIOLOGICAL CONTROL OF FUSARIUM CROWN ROT OF TOMATO 



by 



James J. Marois 



June, 1980 



Chairman: David J. Mitchell 

 Major Department: Plant Pathology 



Fusarium crown rot of tomato was controlled effectively with a 

 composite of several biological agents under growth- chamber, greenhouse, 

 and field conditions. The biological agents were selected for their 

 abilities to proliferate in freshly fumigated soil, to establish high 

 populations in the root zone of the host, and to interact with the 

 pathogen to reduce the incidence of infection or disease. The antago- 

 nists selected were three isolates of Trichoderma harzianum , one isolate 

 of Penicillium restrictum , and one isolate of Aspergillus ochraceus . 



Chlamydo spores of the causal agent, Fusarium oxysporum f . sp. 

 radicis-lycopersici , were formed under axenic conditions so that defined 

 concentrations of specific inocula could be added to freshly fumigated 

 soil. The relationship of inoculum density to incidence of infection 

 was determined under growth-chamber conditions. The inoculum concen- 

 trations of the pathogen at which 50% of the plants were infected were 

 300, 900, and 6500 chlamydo spores per gram of soil which had been 



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