Effect of osmopriming sugar beet seed on exudation and subsequent damping-off caused by Pythium ultimum
1988
Osburn, R.M. | Schroth, M.N.
Control of preemergence damping-off of sugar beets, caused by Pythium ultimum, with NaC1- or polyethylene glycol (PEG)-osmoprimed seed planted in naturally infested field soil was related to a reduction of the rate and incidence of seed colonization by the pathogen. Incidence of colonization of untreated seed was 23.3 and 86.7% by 12 and 24 hr, respectively, whereas colonization of NaC1- and PEG-osmoprimed seed was reduced to 0 and 3.3%, respectively, after 12 hr, and 13.3 and 16.7%, respectively, after 24 hr. Reduced colonization by P. ultimum was related to decreased exudation from osmoprimed seed upon imbibition with water. The amount of carbohydrate exuded from NaC1- and PEG-osmoprimed seed was reduced 98.1 and 91.7%, respec tively, after 60 min, and 41.5 and 55.0%, respectively, after 48 hr of incubation in water compared with untreated seed. The rate of exudation from osmoprimed seed over 48 hr was correlated with the rate of germination, whereas untreated seed did not germinate during the 48-hr incubation period. Disease reduction with NaC1-osmoprimed seed was nullified when the seeds were incubated in exudates before planting. Bacterial population densities of 10(8)-10(9) cfu m1-1 occurred in the NaC1 or PEG osmopriming solutions after 6 days of seed treatment, and residual population densities on seed were 10(4)-10(5) cfu seed-1. The bacterial populations have potential to affect the incidence of damping-off. The incidence of damping-off with NaC1-osmoprimed bacteria-free seed was 20-30% less than with unprimed seed, whereas reductions ranged from 20-54% when bacteria were present on the primed seed.
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