Unique responses of three highly salt-tolerant wild Vigna species against salt stress

Figures & data

Table 1. Salt tolerance of 7 Vigna crop species and 23 wild Vigna species.

Scientific name (crop name)	JP No	Origin^a	Subgenus^b	100 mM^c	200 mM	300 mM
Vigna crops
V. aconitifolia (moth bean)	104332	Pakistan	C	MS	S	S
V. angularis (azuki bean)	37752	Japan	C	S	S	S
V. angularis (azuki bean)	81481	Japan	C	R	S	S
V. mungo (black gram)	109668	India	C	R	S	S
V. radiata (mungbean)	110830	Thailand	C	S	S	S
V. reflexo-pilosa (creole bean)	109684	Philippines	C	MS	S	S
V. umbellata (rice bean)	99485	Japan	C	MS	S	S
V. umbellata (rice bean)	217439	Myanmar	C	S	S	S
African Vigna crop (subgenus Vigna)
V. unguiculata (yardlong bean)	81610	Sri Lanka	V	R	MS	S
Wild Vigna accessions
Asian wild Vigna species (subgenus Ceratotropis)
V. angularis	87910	Japan	C	S	S	S
V. angularis	226665	Laos	C	MR	S	S
V. angularis	110658	Japan	C	MS	S	S
V. aridicola	205894	Sri Lanka	C	MR	S	S
V. dalzelliana	210811	Myanmar	C	MR	S	S
V. exilis	205884	Thailand	C	MR	S	S
V. grandiflora	107862	Thailand	C	S	S	S
V. hirtella	109681	Thailand	C	MS	S	S
V. hirtella	220131	Laos	C	S	S	S
V. minima	107869	Thailand	C	R	S	S
V. mungo	107874	India	C	MR	S	S
V. nakashimea	107879	Korea	C	S	S	S
V. nepalensis	107881	Nepal	C	MS	MS	S
V. radiata	107877	Madagascar	C	MS	S	S
V. radiata	226874	PNG	C	S	S	S
V. reflexo-pilosa	108867	Japan	C	R	S	S
V. riukiuensis	108810	Japan	C	R	MS	MS
V. stipulacea	205892	Sri Lanka	C	R	MS	S
V. subramaniana	229284	India	C	MR	S	S
V. subramaniana	110836	India	C	R	S	S
V. tenuicaulis	109682	Thailand	C	MR	S	S
V. tenuicaulis	227438	Myanmar	C	S	S	S
V. trilobata	205895	Sri Lanka	C	MR	MR	MR
V. trinervia	108840	Thailand	C	MS	S	S
V. umbellata	109675	Thailand	C	MR	S	S
V. umbellata	210644	Thailand	C	S	S	S
V. umbellata	210639	Thailand	C	MS	S	S
African wild Vigna species (subgenera Plectrotropis and Vigna)
V. vexillata	230747	PNG	P	R	MS	MS
V. unguiculata	89083	Nigeria	V	R	MS	S
V. luteola	230741	PNG	V	R	MR	MS
V. marina	201540	Japan	V	R	R	R

^a Origin, PNG: Papua New Guinea

^b Subgenus, C: Ceratotropis, P: Plectrotropis, V: Vigna

^c100 mM: 100 mM NaCl for 2 weeks, 200 mM: 200 mM NaCl for 2 weeks,

300 mM: 300 mM NaCl for 2 weeks.

R (Resistant) = No leaves wilted, MR (Moderately Resistant) = 1–25% of leaves wilted, MS (Moderately Susceptible) = 26–50% of leaves wilted,

S (Susceptible) = 51–100% of leaves wilted.

Figure 1. Intra-specific diversity of salt tolerance indicated as change in percent of susceptible accessions within three wild Vigna species.

One hundred thirty accessions of V. vexillata, 50 accessions of V. luteola and 50 accessions of V. marina were used. Salt tolerance was examined under different concentrations of salt stress, i.e. 250 mM (First 4 weeks) to 350 mM NaCl (Next 4 weeks) for V. vexillata (▲), 300 mM to 400 mM NaCl for V. luteola (■), and 350 mM to 500 mM NaCl for V. marina (●).

Table 2. Comparison of dry-matter weight between the control and NaCl-treated plants.

Species	Acc.	Evaluation	Plot	Leaf DW (g)	Stem DW (g)	Root DW (g)	Shoot DW (g)	Total DW (g)
V. vexillata	V1	Resistant	Control	0.25	0.17	0.04	0.42	0.46
			Treated	0.08 ** (34%)	0.04 ** (23%)	0.03 ** (59%)	0.12 ** (29%)	0.15 ** (32%)
	V5	Sensitive	Control	0.23	0.17	0.05	0.40	0.45
			Treated	0.01 ** (6%)	0.02 ** (10%)	0.01 ** (20%)	0.03 ** (8%)	0.04 ** (9%)
V. luteola	L8	Resistant	Control	0.38	0.33	0.08	0.71	0.79
			Treated	0.24 ** (63%)	0.22 ** (65%)	0.07 * (83%)	0.45 ** (64%)	0.52 ** (66%)
	L9	Resistant	Control	0.25	0.22	0.06	0.47	0.54
			Treated	0.16 ** (63%)	0.15 ** (69%)	0.07 (115%)	0.31 ** (66%)	0.38 ** (71%)
V. marina	M1	Resistant	Control	0.20	0.09	0.04	0.28	0.33
			Treated	0.12 ** (62%)	0.04 ** (46%)	0.04 (83%)	0.16 ** (57%)	0.20 ** (61%)
	M4	Resistant	Control	0.19	0.10	0.05	0.29	0.35
			Treated	0.10 ** (50%)	0.05 ** (49%)	0.04 * (73%)	0.14 ** (50%)	0.18 ** (53%)

Data are the mean value of n = 10, and n = 4 (V5 (Treated)). Numerals in the parenthesis of the treated rows express the percent of each control. Asterisks indicate significant difference between the control and the treated plants at the 0.01 (**) or 0.05 (*) probability level.

Table 3. Dry-matter partitioning of leaf, stem and root as percent (%) in the control and NaCl-treated plants.

Species	Acc.	Evaluation	Plot	Leaf		Stem		Root
				– – – – – – % – – – – – –
V. vexillata	V1	Resistant	Control	53		38		9
			Treated	56	**	27	**	17	**
	V5	Sensitive	Control	52		37		11
			Treated	35		41		24	**
V. luteola	L8	Resistant	Control	48		42		10
			Treated	46	**	41		13	**
	L9	Resistant	Control	47		42		11
			Treated	42	**	40		18	**
V. marina	M1	Resistant	Control	60		26		14
			Treated	61		20	**	19	**
	M4	Resistant	Control	56		29		15
			Treated	52	**	26		21	**

Asterisks indicate significant difference between the control and the treated plants at the 0.01 probability level.

Figure 2. Comparison of the root between the control and NaCl-treated plants in each accession.

Figure 3. Comparison of growth parameters in the control and treated plants. (a) RGR. (b) NAR. (c) LAR. (d) SLA.

White and black bars indicate the control and NaCl-treated plants, respectively. Error bars indicate the standard deviation (n = 10). Numerals in the figure indicate the value of treated plant as percent of control. Asterisks indicate significant difference between the control and the treated plants at the 0.01 (**) probability level.

Figure 4. Relationship between LAR and NAR in the resistant accessions.

White and gray symbols indicate the control and NaCl-treated plants, respectively.

Figure 5. Effect of the NaCl treatment for physiological features of leaves. (a) Photosynthetic rate. (b) Transpiration rate. (c) Stomatal conductance. (d) SPAD value. White and gray bars indicate the control and NaCl-treated plants, respectively. Error bars indicate the standard deviation (Ph: n = 3 and SPAD value: n = 10). Numerals in the figure indicate percent of the control. Asterisks indicate significant difference between the control and the treated plants at the 0.01 (**) or 0.05 (*) probability level.

Figure 6. Na⁺ and K⁺ concentration and Na⁺/K⁺ ratio in the root, stem and leaf of the treated plants. Na⁺ concentration (a), K⁺ concentration (b), Na⁺/K⁺ ratio (c) and Ca²⁺ concentration (d).

Gray, light gray and white bars indicate root, stem and leaf, respectively. Error bars indicate the standard deviation. Different alphabets in the figures indicate significant difference between the root, stem and leaf in each accession at the 0.05 probability level.