Interactions between a plant growth-promoting rhizobacterium and smoke-derived compounds and their effect on okra growth

PAPENFUS H, ; PAPENFUS H, KULKARNI M, ; PAPENFUS H, KULKARNI M, STIRK W,; RENGASAMY K, ; SALOMON MV, ; PICCOLI P, ; BOTTINI R, ; VAN STADEN J.

Journal of Plant Nutrition and Soil Science

WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Año: 2015

1522-2624

Plant growth-promoting rhizobacteria (PGPR) are used in agriculture to improve crop yield. Crude smoke?water (made by bubbling plant-derived smoke through water) stimulates germina- tion and improves seedling growth. Some active compounds have been isolated from smoke with karrikinolide (KAR1) stimulating plant growth and trimethylbutenolide (TMB) being inhibitory. These smoke compounds have great potential in agriculture but their interaction with PGPR is unknown. In the present study, a two-factorial pot trial with three replicates per treatment was de- signed to investigate the interactions between Bacillus licheniformis and two concentrations each of smoke?water, KAR1, and TMB on okra (Abelmoschus esculentus). Growth and physio- logical parameters (chlorophyll, carotenoid, protein, sugar and a-amylase) of okra as well as bac- terial abundance in the rhizosphere were measured after 5 weeks. Application of B. licheniformis and 10?7 M KAR1 significantly improved the shoot biomass and 10?7 M KAR1 also significantly improved leaf area of okra. However, when 10?7 M KAR1 was applied in combination with B. licheniformis, there was an antagonistic effect on plant growth. While TMB had a negative effect on plant growth, a combination treatment of TMB and B. licheniformis overcame the inhibi- tory effect of TMB resulting in plant growth similar to the control plants. All treatments had no effect on chlorophyll, carotenoid, protein and sugar concentrations, while a-amylase activity was significantly elevated in okra root treated with 1:500 v/v smoke?water. Determining the rhizobac- teria populations at harvest showed that all treatments had no significant effect on the rhizo- sphere microbial abundance. The modes of interaction between PGPR and smoke-derived com- pounds need to be further elucidated.