Effect of Rhizobium mechanisms in improving tolerance to saline stress in lettuce plants

Chemical and Biological Technologies in Agriculture

Table 1 Rhizobium sp. GPTR29 volatiles profiling analyzed by GC–MS produced at exponential phase (2 dpi) and stationary phase (5 dpi)

Compounds	RT (min)	Identifier m/z	R match	2 days post-inoculation		5 days post-inoculation
Compounds	RT (min)	Identifier m/z	R match	Normal conditions Area (AU) (10⁷)	100 mM NaCl Area (AU) (10⁷)	Normal conditions Area (AU) (10⁷)	100 mM NaCl Area (AU) (10⁷)
Amides
2-Methylpropionamide^L2	2.17	59	726	n.d	n.d	n.d	3.94
Pyrazoles
6,6-Dimethyltetrahydro-2H-pyran-2-one^L2	2.54	56	854	n.d	n.d	n.d	4.83
Alkanes
3-Methylhexane^L2	2.64	55, 56	895	n.d	n.d	n.d	2.38
3-Ethyl-heptane^L2	10.43	43, 57, 60	871	0.28	n.d	n.d	n.d
3,3-Dimethyl-octane^L2	11.85	43, 57, 70, 71	892	82.0	n.d	n.d	n.d
Ketones
3-Pentanone^L1	2.88	57	871	n.d	n.d	3.17	6.62
1-Mercapto-2-propanone^L2	3.94	43	920	4.86	n.d	n.d	n.d
Acetoin^L1	4.33	45	826	n.d	1.16	n.d	n.d
5-Methyl-3-hexanone^L2	5.36	57	855	n.d	n.d	1.75	5.75
3-Heptanone^L1	8.20	44, 57	762	n.d	0.13	n.d	n.d
6-Methyl-2-heptanone^L2	9.56	43	809	n.d	0.46	n.d	n.d
6-Methyl-5-hepten-2-one^L2	11.17	41, 43, 69, 108	853	0.93	0.26	n.d	n.d
Alcohols
3-Methyl-1-butanol^L1	3.44	55, 70	825	2.91	4.67	3.28	6.57
2-Methyl-1-butanol^L1	3.49	57	864	3.51	1.91	1.96	4.22
3-Methyl-1-butanol, acetate^L1	7.93	43, 70	849	1.89	n.d	n.d	n.d
2-Ethyl-4-methylpentan-1-ol^L2	10.83	55, 57	786	n.d	n.d	0.69	2.10
Sulfides
2,4-Dithiapentane^L2	6.74	58, 61, 108	804	n.d	n.d	n.d	1.07
Benzyl methyl sulfide^L2	14.78	65, 91	785	n.d	n.d	n.d	0.27
Terpenes
α-Pinene^L1	7.98	77, 93	887	0.76	0.05	0.79	2.05
Thioethers
2-Methyl-3-(methylthio)furan^L2	8.35	53, 69, 99, 113	885	n.d	n.d	0.24	1.66

RT, retention time; AU, arbitrary units. n.d., not detected
^L1Compounds (identification by comparison with chemical reference standards under identical analytical conditions). ^L2Putatively annotated compounds (comparison with MS spectral similarity to NIST 14) [54]