EFFECT OF BOTANICAL AROMATIC-COMPOUNDS AND SEED-SURFACE PH ON GROWTH AND COLONIZATION OF COTTON PLANT GROWTH-PROMOTING RHIZOBACTERIA

Citral (3, 7-dimethyl-2, 6-octadienal), furfural (2-furaldehyde) and b enzaldehyde benzoic adelhyde) previously demonstrated control activity against Meloidogyne incognita and fungal diseases on cotton. Plant gr owth-promoting rhizobacteria (PGPR) applied to cotton were previously found to promote plant growth and reduce seedling disease. Studies wer e undertaken to determine if these compounds were compatible with PGPR . In tests with 12 PGPR strains, vapor of citral inhibited in vitro gr owth of mast strains, and vapor of furfural and benzaldehyde, with one exception, killed all but the Bacillus spp. tested. When 0.35 ml kg(- 1) soil of each compound were applied to the soil 9-10 days prior to p lanting the cotton cultivar Deltapine 51, only furfural significantly reduced rhizosphere colonization across all strains from 4.70 colony-f orming units (CFUs)/g of root to 4.42 CFUs/g root. in greenhouse studi es, the low seed-surface pH (2.3) of commercial seed did not reduce ro ot colonization, compared with colonization on roots from seed at pH 5 .4. There were no synergistic interactions between seed-surface pH and any of the compounds. Although previous research indicated that appli cation of both furfural and benzaldehyde increased the proportion of B urkholderia spp. in the soil, there is no indication that they increas ed cotton root colonization by the B. cepacia sti ain tested. These re sults indicate PGPR can be combined with citral and benzaldehyde in in tegrated management systems and that the low seed-surface pH of acid-d elinted cotton will not limit their application.