Biotechnological potential of rhizobial metabolites to enhance the performance of Bradyrhizobium spp. and Azospirillum brasilense inoculants with soybean and maize

AMB Express

Table 3 Nodulation [nodule number (NN) and dry weight (NDW)], plant growth [shoot and root dry weight (SDW, RDW)], N concentration (NC) and total N accumulated in shoots (TNS) of soybean cultivar BRS 245 inoculated or not with Bradyrhizobium japonicum CPAC 15 + B. diazoefficiens CPAC 7 and supplemented or not with genistein (5 μM) or concentrated metabolites (CM) of B. diazoefficiens USDA 110 (BD1) or Rhizobium tropici CIAT 899 (RT1)

Treatment	NN	NDW	SDW	RDW	NC	TNS
	(# pl ^–1)	(mg pl ^–1)	(g pl ^–1)	(g pl ^–1)	(mg N g ^–1)	(mg N pl ^–1)
Non-inoculated control	zero²	zero	0.81 b	0.51 b	6.57 b	5.19 b
Inoculated with Bradyrhizobium	38.0 b	162 a	1.31 a	0.77 a	19.38 a	25.5a
Inoculated + genistein	45.2 a	169 a	1.29 a	0.72 a	21.28 a	28.3 a
Inoculated + CM-BD1 (1 mL L^–1)¹	45.9 a	180 a	1.43 a	0.84 a	21.57 a	29.3 a
Inoculated + CM-BD1 (0.1 mL L^–1)	42.5 a	140 a	1.22 b	0.63 ab	19.07 a	23.7 a
Inoculated + CM-RT1 (1 mL L^–1)	33.2 b	138 a	1.23 b	0.66 ab	20.65 a	25.3 a
Inoculated + CM-RT1 (0.1 mL L^–1)	32.5 b	128 a	1.14 a	0.61 ab	19.81 a	22.9 a

¹ 0.1 and 1.0 mL L^–1 correspond to approximately 10^–9 and 10^–8 M of active compounds, respectively.
² Data represent the means of six replicates and when followed by different letters within the same column are significantly different (p ≤ 0.05, Duncan’s test).
Experiment performed in Leonard jars, with sterile substrate and receiving N-free nutrient solution, under greenhouse conditions. Plants were harvested at 45 days after emergence.