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 benzaldehyde (benzoic adel hyde) previously demonstrated control activity against Meloidogyne incognita and fungal diseases on cotton . Plant growth - promoting rhizobacteria (PGPR) applied to cotton were previously found to promote plant growth and reduce seedling disease . Studies were under taken to determine if these compounds were compatible with PGPR . In tests with 12 PGPR strains , vapor of citral inhibited in vitro growth of most 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 planting the cotton cultivar Deltapine 51 , only furfural significantly reduced rhizosphere colonization across all strains from 4 . 70 colony - forming units (CFUs) / g of root to 4 . 42 CFUs / g root . In greenhouse studies , the low seed - surface pH (2 . 3) of commercial seed did not reduce root 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 application of both furfural and benzaldehyde increased the proportion of Burkholderia spp . in the soil , there is no indication that they increased cotton root colonization by the B. cepacia strain tested . These results indicate PGPR can be combined with citral and benzaldehyde in integrated management systems and that the low seed - surface pH of acid - delinted cotton will not limit their application .