122 



Journal of the Kentucky Academy of Science 66(2) 



Table 2. Dose-dependent inhibition of Botnjtis cinerea by sodium salicylate (SA) in potato-dextrose agar. Data pre- 

 sented are from three replicate experiments, and each value is the mean ± SE colony diameter (mm) of four replicate 

 Petri plates. 



Tnal 



0.0 n 



[iM SA 



0.2 11 



uM SA 



0.5 mM SA 



1.0 mM SA 



2.0 iiiM SA 



5.0 niM SA 



10.0 mM SA 



1 



67.1 



± 0.7 



65.9 



± 0.8 



60.5 ± 1.4 



52.4 ± 1.8 



36.4 ± 1.5 



24.4 



± 1.8 



12.4 ± 1.7 



2 



66.5 



± 0.7 



63.3 



± 0.6 



57.5 ± 0.5 



50.0 ± 0.4 



34.4 ± 1.3 



25.6 



± 1.4 



19.5 ± 2.3 



3 



67.5 



± 2.5 



66.0 



± 1.1 



62.3 ± 1.7 



56.4 ± 1.6 



36.8 ± 1.8 



27.3 



± 2.2 



15.6 ± 3.6 



of the interactive effects of SA and PQ on BC, 

 the fungus grew to fill all six wells per treat- 

 ment that had been amended individually with 

 0.0 or 16.0 mM PQ or 2.0 or 5.0 mM SA, but 

 did not grow in wells amended with 16.0 mM 

 PQ and 2.0 or 5.0 mM SA (data not shown). 



Synergism of SA with Cupric Chloride 



Results of two replicate trials of an experi- 

 ment designed to evaluate the potential inter- 

 active effects of SA and Cu on BC mycelial 

 growth in well-plate culture are presented in 

 Table 4. SA alone caused only a slight reduc- 

 tion in mycelial growth of BC, whereas growth 

 of BC decreased gradually with increasing 

 concentrations of Cu alone, and complete in- 

 hibition of BC growth was obsei*ved only with 

 10.0 mM Cu. In contrast, complete inhibition 

 of BC growth occurred with 5.0 mM Cu (first 

 experiment) or 2.0 mM Cu (second experi- 

 ment) in the presence of 2.0 mM SA. Data 

 regarding the synergistic inhibition of CC 



Table 3. Synergistic inhibition of Botnjtis cinerea my- 

 celial growth in potato-dextrose agar amended with sodi- 

 um salicylate (SA) and/or paraquat (PQ). Data presented 

 are mean colony diameters (mm) ± standard error for 

 three replicate plates per treatment combination. PQ was 

 mixed into partially cooled molten agar prior to pouring 

 into Petri plates (20 ml/plate), whereas SA was introduced 

 as 0.2 ml of a concentrated stock (lOOX) to the centers 

 of plates and permitted to diffuse evenly throughout agar 

 (as assessed by SA fluorescence under ultraviolet illumi- 

 nation). Other abbreviations: OPC, observed percent of 

 control; AMI, additive model of interaction; PPC, pre- 

 dicted percent of control; SYN, synergistic interaction. 





1\) 0.0 1 



iiM 



FQ 4.0 inM 



PQ 8.0 mM 



SA 0.0 mm 



83.3 ± 



0.4 



25.7 ± 2.5 



13.8 ± 3.2 



OPC 



100 





31 



17 



SA 2.0 mM 



67.2 ± 



1.9 



10.0 ± 1.6 



4.2 ± 0.1 



AMI 







(80)(31) 



(80)(17) 



PPC 







25 



14 



OPC 



80 





12 



5 









SYN 



SYN 



spore germination by SA and Cu are present- 

 ed in Table 5. SA alone, at concentrations of 

 0.2 and 0.5 mM, did not affect the frequency 

 of spore germination, whereas 0.75 mM SA 

 inhibited mean germination by 61%, relative 

 to controls. No germination of CG spores was 

 observed in the presence of 1.0 or 2.0 mM SA 

 (data not presented). In the absence of SA, 

 CG spore germination was progressively in- 

 hibited by increasing Cu concentrations. 

 Strong synergistic interactions were observed 

 in combinations of 0.75 mM SA with Cu. For 

 example, although percent spore germination 

 relative to controls (OPC) was 94 and 39 for 

 0.2 mM Cu and 0.75 mM SA, respectively, this 

 combination resulted in an OPC of 4% spore 

 germination, much lower than the 37% ger- 

 mination predicted by the additive model. In- 

 terestingly, 0.2 and 0.5 mM SA effectively 

 abolished the inhibition of spore germination 

 by 0.2, 0.35, and 0.5 mM Cu, and SA thus 

 appeared to act as an antagonist of Cu fungi- 

 toxicity toward CG spores in these combina- 

 tions. 



In a preliminary experiment with PESP, the 

 combination of 2.0 mM SA with 0.5 mM Cu 

 completely prevented spore germination, 

 whereas these concentrations of SA or Cu 

 alone appeared to have little or no effect on 

 the frequency of spore germination (data not 

 shown). In contrast to results obtained with 

 CG, the presence of 0.2 or 0.5 mM SA did 

 not alleviate the moderate inhibition of PESP 

 germ tube elongation occasioned by 0.2 or 0.5 

 mM Cu (data not shown). 



Synergistic Inhibition of BC and PESP by 

 SA in Combination with Culture Fluids of 

 Antagonistic Bacteria 



The antifungal activities of BRCF and WCF 

 toward BC and PESP were synergistically en- 

 hanced by 2.0 mM SA (Table 6; Figure 2). BC 

 growth was not prevented by exposure to SA 



