TABLE 3.

“Short-term” bioassay: control of take-all of wheat by DAPG-producing Pseudomonas strains Q2-87, 1M1-96, and Q8r1-96^a

Treatmentb	Population density of DAPG-producing Pseudomonas (CFU g of root−1)c	Disease severityd
Quincy virgin	ND	5.5 a
Quincy virgin plus Q2-87	1.7 × 107 a	3.7 b
Quincy virgin plus 1M1-96	5.6 × 107 b	3.8 b
Quincy virgin plus Q8r1-96	4.1 × 107 b	3.4 b
Quincy TAD	2.1 × 107 ab	2.7 b

^aWheat seeds were treated with Q2-87, 1M1-96, or Q8r1-96 at a density of approximately 10⁶ CFU seed⁻¹ and sown in raw Quincy virgin soil amended with 0.1% (wt/wt) of an oat grain inoculum of the take-all fungus. Untreated seeds sown in Quincy virgin and Quincy TAD soil served as controls. Disease severity and rhizosphere population densities of introduced or naturally occurring DAPG-producing Pseudomonas strains were determined after 4 weeks of plant growth. 

^bThe Quincy virgin soil is conducive to take-all of wheat, whereas the complementary Quincy TAD soil is suppressive to take-all. 

^cMean values of three replicates of six plants each are presented. Population densities of introduced strains Q2-87, 1M1-96, and Q8r1-96 were determined by dilution plating onto KMB⁺ Rif. Population densities of DAPG-producing Pseudomonas spp. occurring naturally on roots of wheat grown in the Quincy virgin or TAD soil were determined by colony hybridization followed by PCR. Different lowercase letters indicate a statistically significant difference (Tukey's studentized range test, α = 0.05). ND, not detected (below the lower limit of detection of 10⁴ CFU g of root⁻¹). 

^dMean values of six replicates of two plants each are presented. The severity of take-all was rated on a 0-to-8 scale (0 = no disease; 8 = dead plant). Differences between treatments were analyzed by using the Wilcoxon rank-sum test. Different lowercase letters indicate a statistically significant difference (α = 0.05).