Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

Table 8.2 Effects of P. aurantiaca SR1 on plant growth parameters
(shoot and root, fresh and dry weight) in an alfalfa cultivar.
Treatment
Shoot fresh
weight (g)
Coinoculation 0.045 0.002 a
P. aurantiaca SR1 0.031 0.004 b
S. meliloti 3DOh13 0.039 0.004 a
Control N2 0.022 0.002 c
Control 0.018 0.001 c
8.4 Field Experiments with P. aurantiaca SR1 in Wheat (Triticum aestivum L.)j159
Shoot dry
weight (g)
0.029 0.06 a
0.019 0.06 b
0.026 0.11 a
0.005 0.004 c
0.004 0.006 c
Root fresh
weight (g)
0.079 0.03 a
0.025 0.01 b
0.024 0.01 b
0.007 0.001 c
0.005 0.001 c
Root dry
weight (g)
0.014 0.007 a
0.003 0.004 c
0.009 0.003 b
0.005 0.008 b
0.004 0.004 c
Mean SE, means with different letters a,b,c in the same column differ significantly at P < 0.05
(Bonferroni test). Plants were grown for 45 days in the greenhouse.
that promote plant growth is a biochemical property of the PGPR [56]. This explains
the increase in the fresh and dry weight of wheat inoculated with rhizobacteria and
the increase in the capacity of radical absorption with lower doses of nitrogen
fertilizer in gramineous plants [57]. This helps avoid the excess use of urea, which
otherwise contaminates surface and ground water. The experiment in wheat with
P. aurantiaca SR1, formulated as an inoculant by BIAGRO S.A. Laboratory (Buenos
Aires, Argentina), was conduced in a fully randomized block design with seven
replicate blocks for each treatment. Blocks measured 7.2 m 2 (1.20 m wide and 6 m
long) and were 0.20 m apart. Six treatments were established: untreated control,
seeds inoculated with P. aurantiaca SR1, soil fertilized with nitrogen and phosphorus
(dose 100% and 50%) and combination of both doses of fertilizers with
P. aurantiaca SR1.
At stage V5 (30 days after sowing), emergence, length of shoots and roots, volume
of root, fresh and dry mass of shoots and roots were recorded. The parameters of the
yield components evaluated were number of spikes per plant, number of grains per
spike, weight of one thousand grains and yield (kg ha 1 ).
After 30 days of seeding, the positive effect of the inoculation of wheat with
P. aurantiaca SR1 was observed when an increase in emergence, shoot and root
length and radical dry weight occurred (Table 8.3). Inoculation would reduce the
fertilizer use by 50%, as the yield parameters evaluated with the 50% fertilizer dose
gave values similar to the ones obtained with the 100% dose without inoculation.
P. aurantiaca SR1 increased wheat yield by 21% (kg ha 1 ) and 16% in number of
grains per spike (Table 8.4).
Numerous studies refer to the effects of inoculation with PGPR. Field experiments
showed that treatment with Pseudomonas and Bacillus strains increased seedling
emergence in wheat [58]. Pseudomonas species are able to grow in sufficient
quantities on the roots of winter wheat [59]. Inoculation at the time of planting with
Pseudomonas chlororaphis strain 2E3 increased the emergence of spring wheat by 8
and 6% at two different sites in northern Utah [60]. Yield increases in wheat by
PGPR inoculation varied from 18 to 22% in Passo Fundo and from 27 to 28% in Pato
Branco, Brazil [61].