Dy. Han et al., A rapid bioassay for screening rhizosphere microorganisms for their ability to induce systemic resistance, PHYTOPATHOL, 90(4), 2000, pp. 327-332
We developed a rapid and miniaturized bioassay for screening large numbers
of rhizosphere microorganisms for their ability to induce systemic resistan
ce to bacterial leaf spot of radish caused by Xanthomonas campestris pv. ar
moraciae. In this bioassay, Pantoea agglomerans strain E278Ar controlled sy
mptoms of disease as effectively as 2,6-dichloroisonicotinic acid when appl
ied to the roots of seedlings produced in growth pouches in a soilless syst
em. E278Ar essentially did not migrate from seedling roots to the foliage.
This suggests that induction of systemic resistance could best explain the
observed reduction in disease severity. Three mini-Tn5Km-induced mutants of
strain E278Ar were isolated that had lost the ability to induce resistance
. The bioassay also was used to demonstrate that the fungal biocontrol agen
t Trichoderma hamatum strain 382 induces systemic resistance in radish. The
bioassay required only 14 to 18 days from seeding until rating for disease
severity, which is 10 to 14 days less than earlier bioassays.