Suppression of deleterious bacteria by rhizobacteria and subsequentimprovement of germination and growth of tomato seedlings

摘要

Saprophytic bacteria in soil include bene-ficial and deleterious species that havethe potential to influence plant growthand crop yields significantly. The deleteriousbacteria affect plant growth negativelythrough production of phytotoxins~1, butthey do not necessarily parasitize theplant tissue. Other deleterious activitiesinclude alterations of the availability ofwater, ions and plant growth promotingsubstances by changing the root func-tions and/or by limiting root growth~2.Beneficial bacteria on the other hand,promote plant growth and are referred toas 'plant growth promoting rhizobacteria'(PGPR)3. The PGPRs affect plant growthpositively by enhancement of availabilityand uptake of plant nutrients~4, productionof plant growth promoting substances~5and suppression of deleterious bacteria~6.In a field experiment, tomato seedlingsin the nursery exhibited stunted growth.Microbiological analyses of the histo-sphere of such stunted plants yielded twopredominant and distinct bacteria~7. Basedon morphological, physiological and bio-chemical tests~8, both were identified tenta-tively as Bacillus sp. and designated asDHBLandDHBS.