TABLE 4.

Influence of zinc amendment and medium dilution on accumulation of spontaneous gacA regulatory mutants of biocontrol strains from Ghana and Italy^a

Origin	Strain	% of mutantsb			Fisher's LSD0.05
		NBY broth	NBY broth containing zinc	Dilute NBY broth
Ghana	PGNL1	31.7	2.3	1.6	8.0
	PGNR1	16.8	2.6	2.7	8.6
	PGNR4	22.3	4.8	2.3	6.8
Albenga, Italy	PINR2	29.2	1.7	3.0	3.7
	PINR3	40.4	4.0	9.3	14.2

^aNBY broth, NBY broth containing 0.7 mM ZnSO₄ · 7H₄O (zinc), and dilute (0.1×) NBY broth were inoculated with 99% wild-type strain and 1% gacA mutant. Percentages of mutants were determined after 48 h of growth as described in Materials and Methods. 

^bThe strain-medium interaction was significant (P = 0.0113), and data were analyzed based on response to individual main effects. The values are means based on six replicates. The differences within a row or column as determined by Fisher's protected LSD test are significant at P ≤ 0.0289. The Fisher's LSD_0.05 values for NBY broth, NBY broth containing zinc, and dilute NBY broth were 14.7, 1.4, and 2.2, respectively.