Bacterial wilt ratings were performed throughout the course of
the growing season by observing symptoms of the disease on the
tomato plants. Disease incidence was recorded based on the presence
of R. solanacearum detected by isolation as well as visible
symptoms of bacterial wilt on the host, as described below. Symptoms
of bacterial wilt included a complete loss of turgor and total
plant collapse (26). Once plant collapse had occurred, all remaining
fruit on the plant were harvested and each plant was dissected
in order to assess whether R. solanacearum was present within the
stem. Stem segments (2.5 cm long) of wilted plants were excised,
surface sterilized in commercial bleach solution (0.5% sodium
hypochlorite) for 2 min, rinsed in sterilized water, and used to isolate
R. solanacearum from affected plants onto Kelman’s TZC
semiselective agar medium (20). Excised stems of symptomatic
plants were also subjected to an Rs Immunostrip (Agdia, Elkhart,
IN) assay to verify the presence of R. solanacearum.