1Department of Agronomy, Faculty of Agriculture, Atatürk University, Erzurum, Turkey.
2Department of Genetics and Bioengineering, Faculty of Engineering and Architecture, Yeditepe University, Kayısdagi, Atasehir Istanbul, Turkey.
3Departments of Biology and Chemistry, Faculty of Art and Science, Ataturk University, Erzurum, Turkey.
The present study assessed the effect of seed inoculation with single or multiple
plant growth-promoting rhizobacterial (PGPR) strains on yield in spring wheat
(Triticum aestivum spp. vulgare var. Kırık) and barley (Hordeum vulgare cv. Tokak)
plants in both greenhouse and field conditions during the years 2007 and 2008. The
treatments of wheat and barley plants during the first year included: (1) Control
(no inoculation and no fertilizer), (2) Bacillus OSU-142 (B.OSU-142), (3) Bacillus megaterium M3 (B. megaterium M3), (4) Azospirillum brasilense Sp.245 (A. brasilense
Sp.245), (5) Mixed 1 (B.OSU-142 + Bacillus M3 + Azospirillum AB-245),
(6) Bacillus megaterium RC07 (B. megaterium RC07), (7) Paenibacillus polymyxa
RC05, (8) Bacillus licheniformis RC08, (9) mineral nitrogen N1 (80 kg N ha-1) and
(10) N2 (40 kg N ha-1 in the form of urea). In the second year treatments were:
(1) Raoutella terrigena (R. Terrigena), (2) Burkholderia cepacia FS Tur
(B. cepacia FS Tur), (3) B. OSU-142 ARM, (4) B. M3 ARM, (5) A. sp.245 ARM,
(6) P. polymyxa RC14, (7) B. megaterium RC10, (8) Mixed 2 (Bacillus OSU-142+ Bacillus M3+ Azospirillum brasilense sp.245 + 40 kg N ha) in addition to the first
year treatments. Greenhouse and the two years of field trials at two sites showed that
seed inoculation with bacterial strains significantly affected yield, yield components
and quality parameters both in spring wheat and barley. In greenhouse trials, single
inoculations of seeds with PGPRs gave root and shoot weight increases by
11.0-16.5% and 14.4-30.4% in wheat and by 10.3-18.8% and 11.9-21.5% in barley.
Combinations of three bacteria increased root and shoots weight by 18.3-31.5% in
wheat and by 21.4-23.8 in barley and bacterial inoculations also increased grain
yield by 4.3-18.5% in wheat and 8.3-19.1% in barley, respectively. In field conditions wheat grain yields were increased by 25.6-40.4%, 17.4-25.2% and
31.4% while barley seed yield were increased by 16.2-33.7%, 4.2-14.4 and 16.8%
with N fertilizer, single and combinations of PGPR bacteria inoculations compared
to control. Plant-growth responses were variable and depended on the inoculants
strain, plant species and growth parameters evaluated. In conclusion, seed
inoculations with bacteria especially B. OSU-142, A. brasilense sp.245 and
combinations of bacteria may satisfy nitrogen requirements of wheat and barley
under green house and field conditions even in lowland and upland areas. The
present results indicate that the selected bacterial isolates and multiple
combinations did promote the growth and quality of wheat and barley in ways that
could be harnessed to practical benefit for the farmer and consistent with
sustainable and/or organic agricultural practices in Turkey. Keywords: Aridisol; Biofertilizers; Plant growth-promoting bacteria (PGPR).