Efficacy of AAC00-1ΔhrcC as a biocontrol seed treatment for
BFB under greenhouse conditions. Infested watermelon seed
(‘Crimson Sweet’) were generated by hand pollinating (rubbing
pollen from male blossoms onto the stigmatic surfaces), then inoculating
the stigmas of female blossoms of greenhouse-grown
plants with AAC00-1 (approximately 1 × 108 CFU/ml) (40).
Samples (four replicates of 100 seeds) of this seedlot displayed
75% mean BFB seedling transmission and 72% mean germination
using a modified seedling grow-out assay (40). Fruit from
inoculated blossoms were allowed to develop to maturity (35 days
after anthesis) and seed were extracted by hand. After extraction,
seed were air dried at 25°C for 24 h and samples (n = 100 seed)
were vacuum-infiltrated with AAC00-1ΔhrcC at approximately 1 ×
108 CFU/ml or PBS as a negative control as described above.
Treated seed were air dried at approximately 25°C for 24 h and
then assayed for BFB seed-to-seedling transmission under
greenhouse conditions as follows. Seed (n = 100) were planted in
128-cell polystyrene flats (Speedling Inc., Sun City, FL) filled with
pasteurized potting mix (90% composted pine bark and 10%
vermiculite). Flats were incubated in plastic chambers (on a
greenhouse bench) used to generate conditions of 30°C and
approximately 100% RH for 21 days. Seedlings were monitored
daily and germination and BFB seedling transmission percentages
were recorded. The experiment was conducted three times and mean BFB seedling transmission percentages were plotted over
time to generate AUDPC data. AUDPC data were used to conduct
ANOVA and to determine the significance of the effect of
AAC00-1ΔhrcC on BFB seedling transmission using the
Student’s t test.