It is intriguing that when
infiltrated at high concentrations, some of
the BBLS isolates induced a rapid HR-like
response in citrus. Unlike X. citri pv. citri
AW and X. citri pv. aurantifolia strain C (1),
the HR-like responses induced by the BBLS
isolates were more rapid and were not citrus
host specific. Furthermore, no hypersensitive
response and pathogenicity (hrp) genes,
necessary to produce an HR, have been
reported in B. andropogonis. On the other
hand, the culture filtrates of these isolates
from nutrient broth did not exhibit any toxic
effects on citrus (data not shown). Whether
the HR-like phenotype induced by the
BBLS isolates is controlled by Type III
effector genes, toxins, or some other
mechanism entirely remains to be investigated.