6 

 dilution plating of Komada's (l6) medium. The pathogenic isolates were 



identified "by the technique of Sanchez et al. (29) , in which the type 



of lesion on tomato seedlings grown in pathogen- infested water agar is 



used to differentiate the isolates of the pathogen from nonpathogenic 



and wilt inducing F. oxysporum isolates. 



In the greenhouse experiments , 5-wk-old tomato ( * Walter ' ) trans- 

 plants were placed individually in plastic pots (l5-cm diameter) con- 

 taining fumigated soil. A ^-mil-thick plastic film was placed over the 

 soil to simulate the plastic mulch used in production fields. The 

 transplant was planted through a 3-cm hole in the center of the plastic 

 film. Fifty milliliters of a suspension containing 5 X 1(P conidia of 

 each antagonist were poured into the planting hole and over the trans- 

 plant's crown and roots. Ten milliliters of a chlamydospore suspension 

 of the pathogen were injected into the soil at each of two points 

 approximately 7 cm from the plant. The plants were fertilized with 

 half-strength Hoagland's (12) solution every 2 wk and watered when 

 necessary. After 12 wk the root weight, infection incidence, disease 

 incidence, and lesion length were recorded. 



The data presented in this section are means of experiments 

 repeated two times. Each replicate consisted of 48 plants per treat- 

 ment in the growth-chamber studies and 15 plants per treatment in the 

 greenhouse studies. 



Results 

 Percentages of infection, percentages of diseased tomato plants, 

 and mean lesion lengths increased with increasing inoculum levels of the 

 pathogen (Fig. 1, Table l). In the growth-chamber experiments, the 



