XLIII Annual Meeting of SBBq
th
th
Foz do Iguaçu, PR, Brazil, May 17 to 20 , 2014
Setaria Viridis As A Model Grass For The Study Of The PGPR-Grass
Interactions
Pankievicz, V.C.S.1, Amaral, F.P.2, Arisi, A.M.2, Monteiro, R.A.1,Souza, E.M.1,
Pedrosa, F.O.1, Stacey, G.3
1
Dep de Bioquímica e Biologia Molecular, UFPR, Curitiba-PR. 2 Dep de
Ciência de Alimentos, Centro de Ciências Agrárias, UFSC, Florianópolis-SC, 3
Divisions of Plant Science and Biochemistry, C.S. Bond Life Sciences Center,
University of Missouri, Columbia, MO, USA.
INTRODUCTION. Plant growth promoting rhizobacteria (PGPR) are a
promising biotechnological tool to improve agricultural productivity through
biological nitrogen‐fixation and plant growth promotion. OBJECTIVES: We
examined the use of the C4 grass Setaria viridis as a plant model to study the
association with plant growth promoting diazotrophic rhizobacteria,
Herbaspirillum seropedicae and Azospirillum brasilense. MATERIAL AND
METHODS: We screened over 30 genotypes from Setaria viridis. Seedlings
were inoculated with H. seropedicae RAM4 and A. brasilense FP2-7. For plant
growth a 3:1 mixture of turface:vermiculite were used. Two nitrogen regimes
were tested: no nitrogen and 0.5 mM of potassium nitrate. We examined the
plant biomass, root area, number of lateral roots and seeds produced.
Microscopic analyses of fluorescent labeled H. seropedicae and A. brasilense
carrying a nifH:gusA fusion were also performed. RESULTS AND
DISCUSSION: Screening of Setaria genotypes led to identification of three
genotypes that responded strongly to inoculation with both bacteria
(EstepME017, Berlin and A10.1). Bacterial growth promotion was strongest
under no nitrogen regime and was diminished under conditions of increasing
nitrogen addition. Among the most responsive genotypes was A10.1, the
genotype currently being used by the DOE-Joint Genome Institute for genome
sequencing. Microscopy analyses showed that fluorescent H. seropedicae
colonized the internal plant tissues and could be recovered from surface
sterilized roots after 36 days of inoculation. GusA activity was detected in roots
of S. viridis A10.1 inoculated with A. brasilense nifH:gusA strain after 25 days.
Indicating the expression of nif genes. CONCLUSIONS: The data shows that S.
viridis A10.1 may be an experimentally tractable system to study the molecular
mechanisms of bacterial plant growth promotion and associative nitrogen
fixation in a C4 grass species. Measurements of nitrogen fixation, using the
short-lived N13 radioisotope, in S. viridis inoculated with those bacteria, show
the contribution of significant amount of fixed N, thus confirming the potential of
fixing bacteria as biofertilizers.
Key words: Setaria viridis, plant growth promoting rhizobacteria, biological
nitrogen fixation, Herbaspirillum seropedicae, Azospirillum brasilense.
Financial support: CNPq, INCT-Fixação Biológica de Nitrogênio and Ciências
sem Fronteiras.