Open AccessArticle

Analysis of Salt Tolerance of ‘Golden Gold’ Peach Varieties

Yang Li

Xiaoming Sun

Kailong He

Xuebin Jin

Jiachen Leng

Qinglin Huang

Jin Liu

^* and

Yinsheng Sheng

School of Agricultural Science and Technology, Shandong Agricultural and Engineering University, Jinan 250100, China

Author to whom correspondence should be addressed.

Agronomy 2024, 14(12), 3034; https://doi.org/10.3390/agronomy14123034

Submission received: 22 October 2024 / Revised: 11 December 2024 / Accepted: 17 December 2024 / Published: 19 December 2024

(This article belongs to the Section Plant-Crop Biology and Biochemistry)

Download

Browse Figures

Review Reports Versions Notes

Abstract

In this study, the salt tolerance of yellow peach varieties (‘Golden gold’) was identified and analyzed in order to determine varieties with excellent resistance. Photosynthetic parameters, the content of Na⁺, K⁺, and malondialdehyde (MDA), the activity of antioxidant enzymes and other physiological indexes of ‘Golden gold’ peaches were measured after the introduction of salt stress using NaCl. The results showed that under salt stress, the stomatal conductance (Gs), net photosynthetic rate (Pn), transpiration ratio (Tr), water utilization ratio (We), activities of photocooperative enzymes (RuBPCase and FBPase), and K⁺ content in the roots and leaves of all varieties decreased, and among these physiological indexes, there was no significant difference between J2+S and the blank control (J). The contents of MDA and proline in J2+S leaves increased the least, so the effect of salt stress was minimal. The superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, and Na⁺ content in the roots and leaves of all ‘Golden gold’ peach varieties increased, and the difference between J2+S and J was significant, with the largest increase. The results of principal component analysis, membership function analysis, and comprehensive evaluation showed that the salt tolerance of nine ‘Golden gold’ peach varieties was ranked as follows: ‘Golden gold’ No. 2 > ‘Golden gold’ No. 5 > ‘Golden gold’ No. 8 > ‘Golden gold’ No. 6 > ‘Golden gold’ No. 1 > ‘Golden gold’ No. 3 > ‘Golden gold’ Parents > ‘Golden gold’ No. 4 > ‘Golden gold’ No. 7. Correlation analysis showed that Pn and We were positively correlated with the D value (p < 0.01), and Tr, SOD, and CAT were also positively correlated with the D value (p < 0.05). Pn, We, Tr, SOD, and CAT can be used as the main reference indexes for screening the salt-tolerant varieties of the ‘Golden gold’ series.

Keywords:

‘Golden gold’ series; salt tolerance; comprehensive evaluation; photosynthetic characteristics; antioxidant enzyme activity

1. Introduction

In recent years, fresh yellow peaches have become a hot spot in the market. ‘Golden gold’ peaches, with their large size, good quality, sweet and savory flavor, and yellow flesh, are very popular with consumers. However, ‘Golden gold’ peaches form the stigma first, require artificial pollination, and experience problems regarding cultivation technology, affecting the planting yield and benefits. In view of the above problems, we selected and bred ‘Golden gold’ 1–8 fresh yellow peach varieties, grown from late June to early October with different maturity periods in order to meet the consumer demand in different periods of time [1,2,3,4]. However, with the intensification of global climate change, soil salinization has become a major environmental and socio-economic problem worldwide [5], and the yield and quality of yellow peaches have been declining. In addition, there have been few studies on salt stress in yellow peaches, so it is crucial to screen yellow peach varieties for high salt tolerance.

Osmotic stress, sugar accumulation, and ionic toxicity inhibit gas exchange, light energy capture conversion, and carbon fixation in plant stomata under salt stress. Chlorophyll content, net photosynthetic rate, and stomatal conductance were observed to decrease significantly with the increase in salt stress concentration [6]. Salt stress significantly inhibited the net CO₂ assimilation of salt-sensitive tree species, while the net CO₂ assimilation of salt-tolerant tree species did not change significantly [7]. Li Hong and Chen Jianmiao et al. found that the chlorophyll content may increase under low concentration salt stress, which may be due to the “concentration” effect caused by slow growth, or the absorption of Na⁺ may promote chlorophyll synthesis [8].

Ribulose-1, 5-diphosphate carboxylase (RuBPCase) is an important carboxylase in C₃ carbon reactions in photosynthesis and an indispensable oxygenase in photorespiration. It catalyzes the first major carbon fixation reaction in the Calvin cycle of photosynthesis, converting free carbon dioxide from the atmosphere into biological energy storage molecules, such as sucrose [9]. Fructose-1, 6-diphosphatase exists in the cytoplasm and is involved in many metabolic reactions. Its function is to convert fructose-1, 6-diphosphate into fructose-6-phosphate, and it plays a key role in the heterologous metabolism of sugar and the synthesis of the photosynthetic isocompound sucrose. Chloroplast fructose-1,6-diphosphatase FBPase, which is endemic to green plants, is a key enzyme in the Calvin cycle and starch synthesis. Both it and cytoplasmic FBPase are involved in the gluconogenesis pathway in the cytoplasm, playing important regulatory roles in photosynthetic carbon assimilation and allocation which are crucial for plant growth and development. Despite their importance, their regulatory mechanisms are still poorly understood [9].

Malondialdehyde (MDA) content and proline content can reflect the degree of damage to plant leaf cells under salt stress. Membrane lipid peroxidation occurs when the plant growth environment changes and plants are stressed. MDA in plant cells is the final product of membrane lipid peroxidation; it reflects the degree of membrane lipid peroxidation and can indirectly reflect the degree of cell damage after salt stress [10]. Stress can cause the accumulation of reactive oxygen species (ROS) in plants, which are a highly toxic by-product of the aerobic metabolism of plant cells [11,12,13] that can directly cause oxidative stress. Superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) are the three main antioxidant enzymes that can resist oxidative stress in plants [14,15]. Superoxide dismutase mainly clears O₂⁻ and produces H₂O₂, playing a very important role in the resistance to oxidative stress [16]. Salt stress can also lead to nutrient deficiency because high concentrations of Na⁺ and K⁺ inhibit the absorption of other nutrients [17]. This inhibition is demonstrated by the fact that sodium ions can destroy the stability of the soil structure and inhibit the growth and development of plant roots or directly affect absorption by interacting with ion transporters in the root plasma membrane [18].

This study investigated the approved variety of ‘Golden gold’ peach and new varieties of ‘Golden gold’ series 1–8. ‘Golden gold’ No. 1, 2, 3, 4, 5, and 8 have variety registration certificates and ‘Golden gold’ No. 6 and 7 have variety rights. These varieties were selected via crossbreeding and live selection using ‘Golden gold’ peaches as the female parent [1,2,3,4]. The photosynthetic physiological parameters of the leaves and various other physiological parameters were determined to comprehensively evaluate the salt tolerance of the ‘Golden gold’ peach series varieties under salt stress and explore the differences in their salt tolerance. In order to rationally utilize saline soil, high-quality ‘Golden gold’ peach varieties were screened. These findings can help to expand the ‘Golden gold’ peach planting area and provide a theoretical basis and technical support for the rational utilization of saline and alkaline land globally.

2. Materials and Methods

2.1. Experimental Materials

Five ‘Golden gold’ peach (female parent) trees, ‘Golden gold’ No. 1–8, which demonstrated relatively robust growth at similar levels, were selected as scions (branches or buds that are grafted on rootstock). On 3 June 2024, they were grafted with xylem bud grafts, using “Hickory” as the rootstock. The rootstocks were potted and placed in the field. A soil culture pot was used, and river sand was washed with water to remove salt ions before it was loaded into the basin. After washing, the basin was filled with Hoagland culture medium and changed every 4 days. After about 30 days of cultivation, stable grafted fruit trees were selected as test materials. Sodium chloride at a concentration of 0.1 mol/L was applied. The salt was applied continuously for three days to keep the grafted seedlings under moderate salt stress.

During the trial period, the light intensity was constant, the temperature was 5–7 degrees Celsius at night and 15–18 degrees Celsius during the day, and there was no precipitation during the field experiment.

2.2. Methods

2.2.1. Test Treatments

‘Golden gold’ parents, ‘Golden gold’ No. 1, ‘Golden gold’ No. 2, ‘Golden gold’ No. 3, ‘Golden gold’ No. 4, ‘Golden gold’ No. 5, ‘Golden gold’ No. 6, ‘Golden gold’ No. 7, and ‘Golden gold’ No. 8 were treated with 0.1 mol/L NaCl. These treatments were labeled as J+S, J1+S, J2+S, J3+S, J4+S, J5+S, J6+S, J7+S, and J8+S, and the ‘Golden gold’ parent treated with water was set up as the control group, labeled J. The salt-treated and control groups were tested in five replicates. Each repetition was from a grafted fruit tree.

2.2.2. Sampling

Sampling was carried out on the 6th and 12th days after salt treatment. Samples consisting of 3–4 functional leaves (leaves in the center of growth that are metabolically active, located in high-growth areas, and photosynthesizing strongly) [15] were taken from top to bottom of the fruit branches in the middle of the fruit trees. The fibrous root parts of the yellow peach root, located 1.2 to 1.5 m away from the trunk were also sampled. The functional leaves and roots were immediately frozen with liquid nitrogen after collection to analyze the sodium and potassium ion contents, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, and other indicators.

2.2.3. Determination of Photosynthetic Indexes

From top to bottom, 3–4 functional leaves were selected from each plant on days 1, 6, and 12 after salt treatment, respectively. Photosynthetic parameters were measured using the LI-6400XT Portable Photosynthesis System (LI-COR, Lincoln, NE, USA) at 12:00–13:00 on sunny days. These included stomatal conductance (Gs, expressed as mmol/m²/s), intercellular CO₂ concentration (Ci, expressed as ppm), net photosynthetic rate (Pn, expressed as μmol/m²/s), transpiration ratio (Tr, expressed as g/kg), and water utilization ratio (We, expressed as g/kg).

2.2.4. Determination of Activity of Photocooperative Enzymes, Antioxidant Enzymes, and the Contents of MDA, Proline, Na⁺,and K⁺

Photocooperating enzymes, including ribulose-1, 5-diphosphate carboxylase (RuBPCase, expressed as nmol/min/g), and fructose-1, 6-diphosphatase (FBPase, expressed as nmol/min/g), were determined using ELISA kits (GenMed, Beijing, China). All of them were purchased from Hefei Lyer Biotechnology Co., LTD. (Hefei, China), and their product models were LE-Y1799 and LE-Y1739, respectively.

The activity of superoxide dismutase (SOD, expressed as U/g) was determined by means of the nitro-bluetetrazolium (NBT) method [19]. Peroxidase (POD, expressed as U/g) activity was determined by means of the guaiacol method [20]. Catalase CAT activity (expressed as U/g) was determined via the H₂O₂ method [16,20]. According to the thiobarbituric acid method proposed by Velikova et al. (2000) [21], the amount of MDA was measured and expressed as nmol/g protein. Ascorbate peroxidase (APX) activity was measured according to Nakano and Asada (1981) [22].

The proline content was determined by means of the acid ninhydrin method and was expressed as μg/g [23].

For the content determination of Na⁺ and K⁺, expressed as mg/g, refer to Zhao Qi (2019) [24].

2.2.5. Comprehensive Evaluation of Salt Resistance of ‘Golden Gold’ Series Varieties Under Salt Stress

We determined the photosynthetic indexes, antioxidant indexes, and other physiological indexes, such as the root and leaf Na⁺ and K⁺ contents, of yellow peach varieties of the ‘Golden gold’ series under salt stress. By combining principal component analysis, membership function analysis, and comprehensive evaluation, the salt tolerance of the yellow peach was identified, and a salt tolerance evaluation system for the yellow peach was established, providing a reference for the study of the salt tolerance mechanism and breeding of yellow peach varieties.

The calculations were as follows [25]:

(1): Salt tolerance coefficient (β):

Salt tolerance coefficient (β) = Measured values under salt stress/Measured values under control conditions.

(2): Principal component analysis: The salt tolerance coefficient (β) of the individual indicators was analyzed as a principal component and converted into a new independent composite indicator.
(3): Analysis via the affiliation function method. The value of the affiliation function of the composite indicator is obtained using the following formula:

U (X_{j}) = U (X_{j} - X_{m i n}) / U (X_{m a x} - X_{m i n})

(4): Determination of weights: The formula for calculating the weights is as follows:

W_{j} = P_{j} / \sum_{j = 1}^{n} P

(5): The comprehensive evaluation is as follows:

D = \sum_{j = 1}^{n} [U (X_{j}) \times W_{j}]

In these formulae, X_j is the jth composite indicator, X_min is the minimum value of the jth composite indicator, X_max is the maximum value of the jth composite indicator, W_j is the weight of the jth composite indicator among all composite indicators, P_j is the contribution rate of the jth composite indicator of each variety, and D is the composite assessment value of salt tolerance of each variety.

2.3. Data Processing and Analysis

Each parameter was measured five times in parallel. The data obtained from the experiment were subjected to a one-way ANOVA and principal component analysis using SPSS 9.5 statistical software, with the significance level set at α = 0.05. Correlation analysis was performed using the Pearson correlation coefficient method (significance is denoted using * as follows: * stands for p < 0.05, and ** stands for p < 0.01), graphing was performed using Prismchs 9.5 plotting software, and the affiliation function method was used to comprehensively evaluate the salt tolerance of each variety. The three-line table was plotted using Microsoft Office Excel 2016.

3. Results

3.1. Effects of Salt Stress on Photosynthetic Characteristics in ‘Golden Gold’ Peach Leaves

As shown in Figure 1A, on the first day after salt stress, the net photosynthetic rate (Pn) of the J7+S leaves decreased by 87.0% compared with the blank control (J), and the difference was significant. On the sixth day after salt stress, compared with J, the Pn of the J2+S leaves increased by 1.4%, and the Pn of other salt-treated varieties significantly decreased. On the 12th day after salt stress, the Pn of J+S, J4+S, and J6+S decreased by 62.8%, 64.9%, and 63.8% compared with J, respectively, and the difference was significant.

On the first day after salt stress, the leaf stomatal conductance (Gs) of J8+S decreased by 68.4% compared with J, and the difference was significant. On the sixth day after salt stress, compared with J, the Gs of J8+S decreased by 49.0%, while it decreased by 54.9% compared with J2+S, and both differences were significant (Figure 1B). On the 12th day after salt stress, the Gs of J6+S decreased by 77.2%, differing significantly from that of the control.

As shown in Figure 1C, on the first day after salt stress, the intercellular carbon dioxide concentration (Ci) of J2+S was only 0.1% lower than that of J. On the sixth day after salt stress, the Ci of J2+S was only 1.1% lower than that of J. On the 12th day after salt stress, the Ci of J2+S was only 3.6% higher than that of J, and there was no significant difference between J2+S and J between these three days.

As shown in Figure 1D, compared with J, the leaf transpiration ratio (Tr) of J2+S was significantly increased by 125% on day 1 after salt stress. On the 12th day after salt stress, the Tr of J2+S was only 9% lower than that of the control, and the difference was not significant. Meanwhile, the Tr of the other salt-treated varieties was significantly reduced.

As shown in Figure 1E, on the first day after salt stress, compared with J, the leaf water efficiency (We) of J7+S decreased by 44.4%, while it decreased by 86.4% compared with J6+S, and both of these differences were significant. On the sixth day after salt stress, compared with J, the We of J7+S decreased by 79.4%, and the difference was significant. On the 12th day after salt stress, the We values of J2+S and J5+S decreased by 10.5% and 7.9%, respectively, compared with those of J, and the We of the other salt-treated varieties significantly decreased.

The results showed that the photosynthetic characteristics of J2+S leaves were the least affected by salt stress.

3.2. Effects of Salt Stress on Photosynthetic Enzyme Activities in ‘Golden Gold’ Peach Leaves

3.2.1. Effect of Salt Stress on Photosynthetic Enzyme Activity (RuBPCase)

As shown in Figure 2A, on the sixth day after salt stress, compared with J, the RuBPCase activities of J+S, J1+S, J4+S, J5+S, and J8+S were significantly decreased by 59%, 72%, 72%, 58%, and 63%, respectively, while J2+S was only decreased by 11%. On the 12th day after salt stress, compared with J, the RuBPCase activities of J1+S, J4+S, and J5+S were significantly decreased by 74%, 52%, and 56%, respectively, while that of J2+S decreased the least, by 9%.

3.2.2. Effect of Salt Stress on Photosynthetic Enzyme Activity (FBPase)

As shown in Figure 2B, on the sixth day after salt stress, compared with J, the photocooperative enzyme activities (FBPase) of J+S, J4+S, and J6+S were significantly decreased by 68%, 56%, and 50%, respectively; however, that of J2+S was only decreased by 8%. On the 12th day after salt stress, the FBPase activity of J2+S was reduced by 20%, the lowest reduction.

3.3. Effects of Salt Stress on Antioxidant Oxidase Activities and MDA and Proline Contents in ‘Golden Gold’ Peach Leaves

3.3.1. Effects of Salt Stress on Peroxidase (POD) Activity in ‘Golden Gold’ Peach Leaves

As shown in Figure 3A, on the sixth day after salt stress, the POD activity of J2+S increased by 2.5 times compared with that of J, demonstrating the greatest increase. The POD activity of J8+S significantly decreased by 59.1% compared with that of J2+S. On the 12th day after salt stress, the POD activity of J2+S still increased the most to be 2.3 times higher than that of J. Compared with that of J2+S, the POD activity of J+S and J7+S significantly decreased by 66.4% and 67.0%, respectively.

3.3.2. Effects of Salt Stress on Catalase (CAT) Activity in ‘Golden Gold’ Peach Leaves

As can be seen from Figure 3B, on the sixth day after salt stress, the CAT activity of J2+S increased the most, growing by 2.6 times compared to J. Compared with that of J2+S, the CAT activity of J1+S, J4+S, and J7+S significantly decreased by 69.9%, 70.9%, and 70.6%, respectively. On the 12th day after salt stress, the CAT activity of J2+S increased the most, by 3.5 times. Compared with that of J2+S, the CAT activity of J3+S, J4+S, and J7+S significantly decreased by 69.5%, 69.5%, and 75.4%, respectively. The results showed that compared with the same period, the difference between J and J2+S was the most significant.

3.3.3. Effects of Salt Stress on Superoxide Dismutase (SOD) Activity in ‘Golden Gold’ Peach Leaves

As can be seen from Figure 3C, on the sixth day after salt stress, the SOD activity in J2+S increased by 1.8 times compared with J, demonstrating the greatest increase. Compared with that of J2+S, the SOD activity of J3+S, J5+S, and J6+S significantly decreased by 61.6%, 59.7%, and 58.6%, respectively. On the 12th day after salt stress, the SOD activity of J2+S still increased the most, becoming 2.7 times more than that of J. Meanwhile, the SOD activity of J4+S, J6+S, and J8+S significantly decreased by 68.3%, 63.3%, and, 63.6%, respectively. The results showed that the SOD activity of J2+S increased the most and the difference was most significant compared with J.

3.3.4. Effects of Salt Stress on the Activity of Ascorbate Peroxidase (APX) in ‘Golden Gold’ Peach Leaves

As shown in Figure 3D, on the sixth day after salt stress, compared with J, the APX enzyme activities of J2+S, J3+S, J4+S, J5+S, and J6+S leaves significantly increased by 1, 1.3, 1, 1.2, and 1.2 times, respectively. On the 12th day after salt stress, the APX activity of J2+S, J5+S, and J6+S leaves significantly increased by 4.6 times, 1.1 times, and 2.2 times compared to that of J, respectively.

3.3.5. Effects of Salt Stress on Malondialdehyde (MDA) Content in ‘Golden Gold’ Peach Leaves

As shown in Figure 3E, on the sixth day after salt stress, compared with J, the MDA contents in the leaves of J3+S and J5+S significantly increased by 37.4% and 51.5%, respectively. The MDA content of J2+S only increased by 21.2%. On the 12th day after salt stress, the MDA content of J2+S increased the least, increasing by 14% compared with J. The results showed that the difference between J2+S and J was not significant at that time, so the MDA content of J2+S was the least affected by salt stress.

3.3.6. Proline Content in ‘Golden Gold’ Peach Leaves Under Salt Stress

As shown in Figure 3F, on the sixth day after salt stress, the proline content in leaves of J+S, J1+S, J5+S, J6+S, and J8+S increased by 2.2, 2.6, 2.3, 2.0, and 2.4 times, respectively, with significant differences compared with J. However, the proline content of J2+S leaves was only 10% higher than that of J. On the 12th day after salt stress, the proline content in the J+S, J1+S, J5+S, J6+S, and J8+S leaves was 2.8, 3.1, 3.6, 2.4, and 2.7 times higher than in J, respectively, with significant differences. However, the proline content in the J2+S leaves was only 70% higher than in J.

3.4. Na⁺ and K⁺ Accumulation in the Roots and Leaves of ‘Golden Gold’ Peach Under Salt Stress

3.4.1. Na⁺ Accumulation in the Roots of ‘Golden Gold’ Peaches Under Salt Stress

Salt stress can disrupt the ion balance in a plant, thus affecting its absorption of nutrients. As shown in Figure 4A, on the sixth day after salt stress, compared with J, the Na⁺ content in the roots of J+S, J1+S, J2+S, J5+S, and J8+S was significantly increased by 68.6%, 228.8%, 84.8%, 76.3%, and 85.1%, respectively. Only the Na⁺ content of J7+S was 15.6% lower than that of J. However, on the 12th day after salt stress, the Na⁺ content of J5+S and J8+S in the roots significantly increased by 59% and 125.6%, respectively. However, the Na⁺ content of J6+S in the roots was 23.1% lower than that of J.

3.4.2. Na⁺ Accumulation in ‘Golden Gold’ Peach Leaves Under Salt Stress

As shown in Figure 4B, on the sixth day after salt stress, the Na⁺ content in the leaves of J7+S increased the most compared to that of J, reaching 52.6%, and the difference was the most significant. On the 12th day after salt stress, the Na⁺ content of J2+S in the leaves was 11.7% lower than that of J, with a significant difference.

3.4.3. K⁺ Accumulation in the Roots of ‘Golden Gold’ Peaches Under Salt Stress

As shown in Figure 4C, on the sixth day after salt stress, the K⁺ content of J7+S in the roots decreased the most compared with J, being 41.1% lower, and the difference was the most significant. On the 12th day after salt stress, the K⁺ content of J2+S in root decreased the least, by 25.6%, compared with J; meanwhile, the K⁺ content of J7+S in the roots decreased the most, decreasing by 52% and demonstrating a significant difference.

3.4.4. K⁺ Accumulation in ‘Golden Gold’ Peach Leaves Under Salt Stress

As shown in Figure 4D, on the sixth day after salt stress, the K⁺ content in the leaves of J2+S decreased the least, by 10.8%, compared with J. On the 12th day after salt stress, the K⁺ content in the leaves of J2+S decreased the least, by 7.9%, compared with that of J. The results showed that the contents of K⁺ in the leaves of J2+S were least affected by salt stress.

3.5. Comprehensive Evaluation of Salt Tolerance of ‘Golden Gold’ Peach Under Salt Stress Using Membership Function Method

A large number of studies have shown that plants will adapt to a salt stress environment by changing their own growth morphology and physiological and biochemical characteristics, and this adaptation process involves complex changes in the coordinated action of morphological traits and physiological factors among different tissues of the plant; this means that a single indicator cannot reflect the overall salt tolerance of the plant well [26]. Principal component and subordinate function analyses can be used to comprehensively analyze different trait indicators in different varieties of crops, quantitatively evaluating and comprehensively comparing them under the same standard to avoid the one-sidedness and incompleteness that can result from the evaluation of a single indicator, producing results that are more scientific and reliable [27].

The principal components of 17 physiological indexes of ‘Golden gold’ peach cultivars were analyzed under salt stress, and four principal components were extracted. The eigenvalues of each principal component were 7.216, 4.189, 2.042, and 1.475, and the contribution rates were 42.45%, 24.64%, 12.01%, and 8.68%, respectively, with the cumulative contribution rate reaching 87.78%. The contents of Pn, Tr, SOD, and K⁺ in the leaves were the main factors that determined the size of the first principal component. Ci, proline content, root K⁺ content, and root Na⁺ content were the main factors that determined the size of the second principal component. The size of the third component was mainly determined by We, MDA, CAT, and APX, while the size of the fourth component was mainly determined by Gs, FBPase, POD, and MDA (Table 1).

According to the comprehensive evaluation formula, the D value of each variety was obtained. The higher the D value was, the stronger the salt tolerance of the variety was. The results showed that the salt tolerance of the nine ‘Golden gold’ peach varieties was ranked as follows: ‘Golden gold’ No. 2 > ‘Golden gold’ No. 5 > ‘Golden gold’ No. 8 > ‘Golden gold’ No. 6 > ‘Golden gold’ No. 1 > ‘Golden gold’ No. 3 > ‘Golden gold’ Parents > ‘Golden gold’ No. 4 > ‘Golden gold’ No. 7 (Table 2).

The correlation analysis of 13 physiological indexes and the D value of the comprehensive evaluation of the ‘Golden gold’ peach varieties under salt stress showed that We, POD, SOD, and CAT were significantly (p < 0.05) positively correlated with Pn, and the correlation coefficients were 0.768, 0.684, 0.795, and 0.675, respectively. Tr was significantly (p < 0.05) positively correlated with Gs, and the correlation coefficient was 0.684. There was a significant (p < 0.05) positive correlation between the K⁺ content in the roots and Ci, and the correlation coefficient was 0.79. There was a significant (p < 0.05) positive correlation between CAT and We, and the correlation coefficient was 0.754. The content of Na⁺ in the leaves was significantly negatively correlated with that of We (p < 0.01), and the correlation coefficient was −0.82. There was a significant positive correlation between SOD and Tr (p < 0.01), and the correlation coefficient was 0.89. The APX and leaf K⁺ content were significantly positively correlated with RuBPCase (p < 0.01), and the correlation coefficients were 0.886 and 0.948, respectively. FBPase and RuBPCase were positively correlated (p < 0.05), and the correlation coefficient was 0.752. There was a significant positive correlation between APX and FBPase (p < 0.01), and the correlation coefficient was 0.854. The content of K⁺ in the leaves was positively correlated with FBPase (p < 0.05), and the correlation coefficient was 0.727. There was a significant negative correlation between proline and FBPase (p < 0.05), and the correlation coefficient was −0.705. APX and POD showed a significant positive correlation (p < 0.05), and the correlation coefficient was 0.712. The content of K⁺ in the leaves was positively correlated with SOD (p < 0.05), and the correlation coefficient was 0.711. There was a significant (p < 0.05) positive correlation between the K⁺ content in the leaves and APX, and the correlation coefficient was 0.796. There was a significant negative correlation between the Na⁺ content in the leaves and the Na⁺ content in the roots (p < 0.05), and the correlation coefficient was −0.776. Pn and We were significantly positively correlated with the D value (p < 0.01), and the correlation coefficients were 0.908 and 0.887, respectively. Tr, SOD, and CAT were significantly (p < 0.05) positively correlated with the D value, and the correlation coefficients were 0.697, 0.771, and 0.775, respectively. The Na⁺ content in the leaves showed a significant (p < 0.05) negative correlation, and the correlation coefficient was −0.696 (Table 3).

4. Discussion

4.1. Effect of Salt Stress on Photosynthetic Characteristics of ‘Golden Gold’ Peach Leaves

In this experiment, considering that seedlings are more sensitive to salt stress [28], the fruit trees were tested one month after grafting, The leaves were young when they were sampled 1d after salt stress, and they grew gradually at 6d and 12d after salt stress; perhaps Pn, Tr, and We were gradually increased at 1d, 6d, and 12d after salt stress for this reason.

In addition, plants demonstrate different developmental characteristics at different time scales under salt stress. To understand these temporal differences in response to salinity, Munns proposed the concept of a “two-stage growth response to salinity”. After exposure to salinity, the first phase of growth decline occurs quickly (within minutes), a response that is due to a change in the cell–water relationship caused by external osmosis that reduces the plant’s ability to take up water. After a brief decline in the leaf growth rate, it gradually recovers until a new steady state is reached [29]. The second stage is slower than the first, and the response time may take days, weeks, or months, which is associated with plant salt accumulation and causes salinity toxicity in old leaves [29]. In this experiment, the grafted seedlings of each variety were probably in the first stage of salt stress on the first day after salt stress was induced.

Salt stress affects photosynthesis mainly through stomatal and non-stomatal factors [30]. The intercellular carbon dioxide concentration (Ci) of J, J+S, J1+S, J2+S, J4+S, and J6+S was the lowest on the sixth day after salt stress; in most cases, salt stress decreases the potassium ion content, causes water loss in leaves, or increases abscisic acid content, etc., which can lead to stomatal closure in plants subjected to salt stress [30]. Stomatal closure leads to a decrease in the concentration of intercellular carbon dioxide, resulting in salt resistance.

The activities of photosynthetic enzymes such as ribulose 1,5-bisphosphate carboxylase (RuBPCase) and fructose-1,6-bisphosphatase (FBPase) are closely related to the integrity of photosynthetic apparatus [31,32]. As a C₃ plant, the yellow peach mainly uses RuBPCase to fix CO₂. RuBPCase is an important leaf protein that plays a decisive role in plant photosynthesis and is often called the rate-limiting enzyme of photosynthesis [33,34]. Ceusters et al. [34,35] found that RuBPCase activity plays a key role in maintaining photosynthesis under environmental stress. The results showed that the photocooperative enzymes’ activities in J2+S leaves were always higher than in the other varieties and were the least affected by salt stress.

4.2. Effects of Salt Stress on Antioxidant System in ‘Golden Gold’ Peach Leaves

In general, malondialdehyde and proline contents increase with an increasing salt concentration [23]. A higher malondialdehyde content represents greater cell membrane permeability and more severe cell damage. The content of osmoregulatory substances, such as proline, reflects the degree of plant response to adversity and the degree of membrane lipid peroxidation, in addition to providing an indication of stress tolerance. Proline is dipolar and its hydrophilic end binds to water, thus allowing the protein to bind more water [24]. The results showed that the MDA and proline contents in the leaves of nine species of yellow peaches increased under salt stress compared with the control. This was consistent with Lei Chengjun’s research results, which showed that MDA and proline contents in plant leaves increase under salt stress [36].

Peroxidase and catalase are mainly the products of SOD elimination and the mitigation of membrane oxidative damage. Salt-tolerant plants and salt-sensitive plants have different responses to salt stress; under mild and moderate salt stress, the activities of the four enzymes (SOD, POD, CAT, and APX) all show an upward trend [21]. This is consistent with our findings. Moreover, the activities of POD, CAT, and SOD in the J2+S, J3+S, J5+S, and J6+S leaves increased with the prolongation of salt stress, showing strong salt tolerance.

4.3. Effects of Salt Stress on Na⁺ and K⁺ Accumulation in the Roots and Leaves of ‘Golden Gold’ Peaches

When plants are exposed to salt stress, the increase in Na⁺ leads to salt injury. When the Na⁺ concentration increases, it will delay or damage the digestion and absorption of water and nutrients in plants and damage the normal function of plasma membrane transporters, resulting in plant metabolism disorder. This will weaken the uptake rate of mineral ions such as K⁺, Ca²⁺, Mg²⁺, and Fe²⁺ by the plant, thus inhibiting its growth [37].

Changes in the intracellular sodium and potassium ion content directly reflect the degree of ion toxicity to which the plant cells are subjected [38]. Plant cells demonstrate high sensitivity to the toxicity of salt ions, and an ion imbalance in plant cells under salt stress can lead to a lack of nutrients and the failure to grow and develop normally. When there is too much Na⁺ in the cell and little K⁺ uptake, it leads to competition between Na⁺ and K⁺ for K⁺ binding sites, resulting in Na⁺ toxicity [39]. Qin Wei et al. found that when plants are subjected to salt stress, the content of Na⁺ and K⁺ in the plant can be used to measure the plant’s salt resistance [18]. In this experiment, compared to other varieties, the K⁺ content in the roots and leaves of J2+S was much higher than in other varieties and basically remained stable and minimally affected. The Na⁺ content in the roots and leaves of J2+S was the lowest and displayed a decreasing trend as a whole. Salt stress affects the uptake of other nutrients by plants, especially due to Na⁺ competition for K⁺ binding sites [28]. In this study, although J7+S had a lower root Na⁺ content compared to the blank control J, salt stress caused damage to the plant and affected its K⁺ uptake, resulting in a low K⁺ content and a high Na⁺/K⁺ ratio. In conclusion, the resistance of ‘Golden gold’ No. 2 (J2) to salt stress was the strongest, and the resistance of ‘Golden gold’ No. 7 (J7) to salt stress was the weakest.

5. Conclusions

This study explored the salt tolerance differences among the ‘Golden gold’ series varieties of yellow peach under salt stress and comprehensively evaluated the extent of the yellow peach’s salt tolerance, providing a theoretical basis and technical support for the rational utilization of saline and alkaline land globally, the selection and breeding of high-quality yellow peach varieties, and the expansion of yellow peach planting areas.

Author Contributions

Conceptualization, Y.L., K.H., J.L. (Jin Liu) and Y.S.; Methodology, Y.L.; Software, Y.L.; Investigation, Y.L., K.H., X.J., X.S., J.L. (Jiachen Leng), Q.H., J.L. (Jin Liu) and Y.S.; Writing—original draft, Y.L., K.H., X.J., X.S., J.L. (Jiachen Leng), Q.H., J.L. (Jin Liu) and Y.S.; Formal analysis, Y.L., K.H., X.J., X.S., J.L. (Jiachen Leng), Q.H. and Y.S.; Validation, Y.L., K.H. and X.J.; Writing—review and editing, Y.L., K.H., X.J., X.S., J.L. (Jiachen Leng), Q.H. and Y.S.; Data curation, J.L. (Jiachen Leng), Q.H. and J.L. (Jin Liu); Supervision, J.L. (Jin Liu); Funding acquisition, J.L. (Jin Liu); Project administration, J.L. (Jin Liu); Resources, Y.S. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Collaborative Extension Program for Major Agricultural Technologies in Shandong Province (SDNYXTTG-2024-19).

Data Availability Statement

The data presented in this study are available on request from the corresponding author due to privacy.

Conflicts of Interest

The authors declare no conflicts of interest.

References

Liu, J.; Xue, G.H.; Liu, C.S. Selection and breeding of new peach yellow flesh variety ‘Golden Gold No. 2’. China Fruit Tree 2019, 83–84. [Google Scholar] [CrossRef]
Liu, J.; Peng, F.; Zhang, A.; Yang, C.; Li, G. Selection and breeding of a new off-core yellow peach variety ‘Golden Gold No.6’. North Hortic. 2022, 158–160. Available online: https://caod.oriprobe.com/articles/62914382/li_he_huang_tao_xin_pin_zhong__jin_huang_jin_6_hao.htm (accessed on 10 December 2024).
Liu, J.; Yang, C.; Dong, M.; Zhang, A.; Li, G.; Liu, C.; Zhou, Z. Selection and breeding of a new peach variety ‘Golden Gold No.3’ with very late maturity and yellow flesh. China Fruit Tree 2020, 101–102. [Google Scholar] [CrossRef]
Liu, J.; Yang, C.; Wang, H.; Dou, Q.; Wang, F.; Luan, Y.; Lu, Z. Selection and breeding of a new late-maturing yellow-fleshed variety of peach ‘Golden Gold’. China Fruit Tree 2016, 72–73. [Google Scholar] [CrossRef]
Hassani, A.; Azapagic, A.; Shokri, N. Global predictions of primary soil salinization under changing climate in the 21st century. Nat. Commun. 2021, 12, 6663. [Google Scholar] [CrossRef] [PubMed]
López-Climent, M.F.; Arbona, V.; Pérez-Clemente, R.M.; Gómez-Cadenas, A. Relationship between salt tolerance and photosynthetic machinery performance in citrus. Environ. Exp. Bot. 2008, 62, 176–184. [Google Scholar] [CrossRef]
Sudhir, P.; Murthy, S.D. Effects of salt stress on basic processes of photosynthesis. J. Catal. 2004, 42, 481–486. [Google Scholar] [CrossRef]
Wu, W.; Zhang, Q.; Ervin, E.H.; Yang, Z.; Zhang, X. Physiological Mechanism of Enhancing Salt Stress Tolerance of Perennial Ryegrass by 24 Epibrassinolide. Front. Plant Sci. 2017, 8, 1017. [Google Scholar] [CrossRef] [PubMed]
Mei, Y.; Li, H.; Xie, J.; Luo, H. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Plant Physiol. 2007, 43, 363–368. [Google Scholar]
Koushesh, M.; Moradi, S. Sodium nitroprusside (SNP) spray to maintain fruit quality and alleviate postharvest chilling injury of peach fruit. Sci. Hortic. 2017, 216, 193–199. [Google Scholar] [CrossRef]
Sharma, P.; Jha, A.B.; Dubey, R.S.; Pessarakli, M. Reactive oxygen species, oxidative damage, and antioxidative defense mechanism in plants under stressful conditions. J. Bot. 2012, 2012, 217037. [Google Scholar] [CrossRef]
Baxter, A.; Mittler, R.; Suzuki, N. ROS as key players in plant stress signaling. J. Bot. 2014, 65, 1229–1240. [Google Scholar]
Das, K.; Roychoudhury, A. Reactive oxygen species (ROS) and response of antioxidants as ROS-scavengers during environmental stress in plants. Front. Environ. Sci. 2014, 2, 53. [Google Scholar] [CrossRef]
Wu, Z.; Zhao, X.; Sun, X.; Tan, Q.; Tang, Y.; Nie, Z.; Qu, C.; Chen, Z.; Hu, C. Antioxidant enzyme systems and the ascorbate-glutathione cycle as contributing factors to cadmium accumulation and tolerance in two oilseed rape cultivars (Brassica napus L.) under moderate cadmium stress. Chemosphere 2015, 138, 526–536. [Google Scholar] [CrossRef]
Ma, Y.Y.; Huang, D.D.; Chen, C.B.; Zhu, S.H.; Gao, J.G. Regulation of ascorbate-glutathione cycle in peaches via nitric oxide treatment during cold storage. Sci. Hortic. 2019, 247, 400–406. [Google Scholar] [CrossRef]
Kim, Y.H.; Khan, A.L.; Waqas, M.; Lee, I.J. Silicon regulates antioxidant activities of crop plants under abiotic-induced oxidative stress: A review. Front. Plant Sci. 2017, 8, 510. [Google Scholar] [CrossRef] [PubMed]
Silberbush, M.; Ben-Asher, J. Simulation study of nutrient uptake by plants from soilless cultures as affected by salinity buildup and transpiration. Plant Soil 2001, 233, 59–69. [Google Scholar] [CrossRef]
Tester, M.; Davenport, R. Na⁺ tolerance and Na⁺ transport in higher plants. Ann. Bot. 2003, 91, 503–527. [Google Scholar] [CrossRef]
Prochazkova, D.; Sairam, R.K.; Srivastava, G.C.; Singh, D.V. Oxidative stress and antioxidant activity as the basis of senescence in maize leaves. Plant Sci. 2001, 161, 765–771. [Google Scholar] [CrossRef]
Cakmak, I.; Marschner, H. Magnesium deficiency and high light intensity enhance activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in bean leaves. Plant Physiol. 1992, 98, 1222–1227. [Google Scholar] [CrossRef] [PubMed]
Velikova, V.; Yordanov, I.; Edreva, A. Oxidative stress and some antioxidant systems in acid rain-treated bean plants protective role of exogenous polyamines. Plant Sci. 2000, 151, 59–66. [Google Scholar] [CrossRef]
Nakano, Y.; Asada, K. Hydrogen peroxide is scavenged by ascorbate-specific peroxidase in spinach chloroplasts. Plant Cell Physiol. 1981, 2, 867–880. [Google Scholar]
Balal, R.M.; Khan, M.M.; Shahid, M.A.; Mattson, N.S.; Abbas, T.; Ashfaq, M.; Garcia-Sanchez, F.; Ghazanfer, U.; Gimeno, V.; Iqbal, Z. Comparative studies on the physiobiochemical, enzymatic, and ionicmodifications in salt-tolerant and salt-sensitive citrus rootstocks under NaCl stress. J. Am. Soc. Hortic. Sci. 2012, 137, 86–95. [Google Scholar] [CrossRef]
Zhao, Q.; Zhang, Z.J.; Li, C.; Zou, Y.J. Effects of different rootstocks on nutrient uptake and utilization of “honey crisp” apple seedlings under drought conditions. J. Northwest AF Univ. (Nat. Sci. Ed.) 2019, 47, 103–111. [Google Scholar]
Ma, R.J.; Zhang, B.B.; Cai, Z.X.; Shen, Z.J.; Yu, M.L. Evaluation of peach rootstock waterlogging tolerance based on the responses of the photosynthetic indexes to continuous submergence stress. Acta Hortic. Sin. 2013, 40, 409–416. [Google Scholar]
Liu, Y.; Wu, J.; Xu, Z.; Shen, Z.; Xia, Y.; Wang, G.; Chen, Y. Identification method of salt tolerance of wheat at germination and seedling stage under artificial seawater stress. Acta Phytophysiol. Sin. 2014, 50, 214–222. [Google Scholar]
Gao, X.; Zhu, L.; Su, Y. Comprehensive evaluation of salt tolerance of sweet sorghum at booting stage based on membership function method. J. South. Agric. 2018, 49, 1736–1744. [Google Scholar]
Yokoi, S.; Quintero, F.J.; Cubero, B.; Ruiz, M.T.; Bressan, R.A.; Hasegawa, P.M.; Pardo, J.M. Differential expression and function of Arabidopsis thaliana NHX Na⁺/H⁺ antiporters in the salt stress response. Plant J. 2002, 30, 529–539. [Google Scholar] [CrossRef] [PubMed]
Munns, R. Comparative Physiology of Salt and Water Stress. Plant Cell Environ. 2002, 25, 239–250. [Google Scholar] [CrossRef]
Cramer, G.R.; Quarrie, S.A. Abscisic acid Is correlated with the leaf growth inhibition of Four genotypes of maize differing in Their Response to Salinity. Funct. Plant Biol. 2002, 29, 111–115. [Google Scholar] [CrossRef]
Yin, F.; Zhang, S.; Cao, B.; Xu, K. Low pH alleviated salinity stress of ginger seedlings by enhancing photosynthesis, fluorescence, and mineral element contents. PeerJ 2021, 11, e10832. [Google Scholar] [CrossRef] [PubMed]
Hazra, S.; Henderson, J.N.; Liles, K.; Hilton, M.T.; Wachter, R.M. Regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activase: Product inhibition, cooperativity, and magnesium activation. J. Biol. Chem. 2015, 290, 24222–24236. [Google Scholar] [CrossRef]
Chen, G.Y.; Yu, G.L.; Chen, Y.; Xu, D.Q. A study on the observation method of photosynthesis response to light and carbon dioxide. J. Plant Physiol. Mol. Biol. 2006, 32, 691–696. [Google Scholar]
Andersson, I.; Taylor, T.C. Structural framework for catalysis and regulation in ribulose-1,5-bisphosphate carboxylase/oxygenase. Arch. Biochem. Biophys. 2003, 414, 130–140. [Google Scholar] [CrossRef] [PubMed]
Ceusters, J.; Borland, A.M.; Londers, E.; Verdoodt, V.; Godts, C.; De Proft, M.P. Diel shifts in carboxylation pathway and metabolite dynamics in the CAM bromeliad Aechmea ‘Maya’ in response to elevated CO₂. Ann. Bot. 2008, 102, 389–397. [Google Scholar] [CrossRef]
Lei, C. Effects of Salt Stress on Growth Physiological Indexes and Disease Resistance of Red Globe Grape Seedlings. Master’s Thesis, Gansu Agricultural University, Lanzhou, China, 2012. [Google Scholar]
Parvaiz, A.; Satyawati, S. Salt stress and phyto-biochemicalresponses of plants a review. Plant Soil Environ. 2008, 54, 88–99. [Google Scholar] [CrossRef]
Walker, R.R.; Blackmore, D.H.; Clingeleffer, P.R.; Correll, R.L. Rootstock effects on salt tolerance of irrigated field grown grape vines (Vitis vinifera L cv. Sultana). 1. Yield and vigour inter-relationships. Aust. J. Grape Wine Res. 2002, 8, 3–14. [Google Scholar] [CrossRef]
Hasegawa, P.M.; Bressan, R.A.; Zhu, J.K.; Bohnert, H.J. Plant cellular and molecular responses to high salinity. Plant Physiol. 2000, 51, 463–499. [Google Scholar]

Figure 1. Effect of salt stress on photosynthetic parameters Pn (A), Gs (B), Ci (C), Tr (D), and water efficiency (E) of ‘Golden gold’ peach leaves. Letters a, b, c, d, e, and f are used to indicate significant differences, and different small letters indicate significance at p < 0.05 level. Bars in figures represent SD. J represents parent plant and indicates water-treated blank control; J1–J8 indicate new varieties of ‘Golden gold’ series 1–8; J+S, J1+S, J2+S, J3+S, J4+S, J5+S, J6+S, J7+S, and J8+S indicate they were treated with 0.1 mol/L NaCl. 1d indicates the 1st day after salt stress; 6d indicates the 6th day after salt stress; and 12d indicates the 12th day after salt stress.

Figure 2. Effect of salt stress on photocooperative enzyme activity. RuBPCase (A) and FBPase (B) of ‘Golden gold’ peach leaves. The letters a, b, c, d, e, f, g, and h are used to indicate the significance of differences, and different small letters indicate significance at the p < 0.05 level. The bars in the figures represent SD. J represents the parent and indicates the blank control, which was treated with water; J1–J8 indicate the new varieties of ‘Golden gold’ series 1–8; and J+S, J1+S, J2+S, J3+S, J4+S, J5+S, J6+S, J7+S, and J8+S indicate they were treated with 0.1 mol/L NaCl. 6d indicates the 6th day after salt stress; 12d indicates the 12th day after salt stress.

Figure 3. Effect of salt stress on antioxidant oxidase activities and MDA and proline contents in ‘Golden gold’ peach leaves. POD (A), CAT (B), SOD (C), APX (D), MDA (E), Pro (F) of ‘Golden gold’ peach leaves. The letters a, b, c, d, e, f, g, h, i, and j are used to indicate the significance of differences, and different small letters indicate significance at the p < 0.05 level. The bars in the figures represent SD. J represents the parent and indicates the blank control, which was treated with water; J1–J8 indicate the new varieties of ‘Golden gold’ series 1–8; J+S, J1+S, J2+S, J3+S, J4+S, J5+S, J6+S, J7+S, and J8+S indicate they were treated with 0.1 mol/L NaCl. 6d indicates the 6th day after salt stress; 12d indicates the 12th day after salt stress.

Figure 4. Na⁺ and K⁺ accumulation in the roots and leaves of ‘Golden gold’ peach under salt stress. (A) Na⁺ in roots. (B) Na⁺ in leaves. (C) K⁺ in roots. (D) K⁺ in leaves. The letters a, b, c, d, e and f are used to indicate the significance of differences, and different small letters indicate significance at the p < 0.05 level. The bars in the figures represent SD. J represents the parent and indicates the blank control, which was treated with water; J1–J8 indicate the new varieties of ‘Golden gold’ series 1–8; J+S, J1+S, J2+S, J3+S, J4+S, J5+S, J6+S, J7+S, and J8+S indicate they were treated with 0.1 mol/L NaCl. 6d indicates the 6th day after salt stress; 12d indicates the 12th day after salt stress.

Table 1. Coefficient and contribution of each comprehensive index.

	Pn	Gs	Ci	We	Tr	RuBPCase	FBPase	Pro	MDA	POD	SOD	CAT	APX	K⁺ in Roots	K⁺ in Leaves	Na⁺ in Roots	Na⁺ in Leaves	Eigen-value	Contribution Rate	Cumulative Contribution Rate
PC1	0.125	0.051	0.059	0.078	0.104	0.11	0.104	−0.085	−0.071	0.098	0.125	0.097	0.108	0.061	0.118	−0.017	−0.027	7.216	42.449	42.45%
PC2	0.063	0.077	0.144	0.133	0.065	−0.105	−0.115	0.142	0.042	−0.038	0.056	0.073	−0.111	0.151	−0.075	0.206	−0.217	4.189	24.641	67.09%
PC3	0.059	−0.298	−0.073	0.281	−0.182	0.13	−0.008	0.169	0.283	0.059	−0.124	0.221	0.183	−0.155	0.025	−0.068	−0.155	2.042	12.01	79.10%
PC4	0.024	0.364	−0.42	0.061	0.172	−0.056	0.265	0.125	0.254	0.222	−0.083	−0.247	0.076	−0.112	−0.009	0.178	−0.123	1.475	8.68%	87.78%

Table 2. Comprehensive index value, weights, U (X_j), D value, and sequence of salt tolerance of each variety.

Treatments	PC1	PC2	PC3	PC4	U(X₁)	U(X₂)	U(X₃)	U(X₄)	D Value	Arrange in Order
J+S	−0.64	0.60	−0.41	−1.22	0	0.77	0.22	0	0.245	7
J1+S	−0.62	1.39	−1.09	0.44	0.01	1	0	0.51	0.335	5
J2+S	2.62	0.38	−0.19	−0.04	1	0.71	0.29	0.36	0.754	1
J3+S	−0.32	−0.62	−0.14	0.33	0.10	0.41	0.31	0.47	0.253	6
J4+S	−0.23	−0.48	−1.03	−0.85	0.13	0.45	0.02	0.11	0.202	8
J5+S	−0.34	0.38	0.79	2.04	0.09	0.70	0.61	1	0.426	2
J6+S	−0.18	−0.38	2.02	−0.99	0.14	0.48	1	0.07	0.350	4
J7+S	−0.08	−2.02	−0.61	0.52	0.17	0	0.16	0.53	0.159	9
J8+S	−0.21	0.75	0.67	−0.24	0.13	0.81	0.56	0.30	0.400	3
weights					0.48	0.28	0.14	0.1	0.48

Table 3. Correlation coefficients among indexes and D values of different ‘Golden gold’ peach varieties under salt stress.

	Pn	Gs	Ci	We	Tr	Rub	FBP	Pro	MDA	POD	SOD	CAT	APX	K⁺ in Roots	K⁺ in Leaves	Na⁺ in Roots	Na⁺ in Leaves
Pn	1
Gs	0.307	1
Ci	0.511	0.096	1					.
We	0.768 *	0.051	0.433	1
Tr	0.635	0.684 *	0.352	0.37	1
Rub	0.564	−0.034	0.04	0.308	0.44	1
FBP	0.572	0.284	−0.175	0.184	0.559	0.752 *	1
Pro	−0.422	−0.127	−0.125	0.183	−0.263	−0.578	−0.705 *	1
MDA	−0.392	−0.221	−0.372	0.1	−0.508	−0.355	−0.313	0.638	1
POD	0.684 *	0.351	0.086	0.426	0.325	0.473	0.746 *	−0.604	−0.082	1
SOD	0.795 *	0.465	0.635	0.467	0.89 **	0.601	0.544	−0.468	−0.616	0.427	1
CAT	0.675 *	−0.035	0.619	0.754 *	0.37	0.622	0.187	−0.1	−0.143	0.346	0.64	1
APX	0.655	−0.061	−0.073	0.432	0.346	0.886 **	0.854 **	−0.614	−0.286	0.712 *	0.479	0.504	1
K+ in roots	0.532	0.551	0.79 *	0.362	0.41	−0.067	−0.036	−0.164	−0.157	0.375	0.571	0.434	−0.128	1
K+ in leaves	0.626	0.23	0.097	0.292	0.6	0.948 **	0.727 *	−0.579	−0.489	0.462	0.711 *	0.603	0.796 *	0.085	1
Na+ in roots	0.165	0.381	0.272	0.394	0.33	−0.498	−0.398	0.636	0.083	−0.315	0.124	−0.028	−0.489	0.323	−0.332	1
Na+ in leaves	−0.463	−0.262	−0.469	−0.82 **	−0.332	0.176	0.225	−0.568	−0.291	−0.081	−0.291	−0.488	0.128	−0.51	0.107	−0.776 *	1
D	0.908 **	0.392	0.49	0.887 **	0.697 *	0.508	0.464	−0.115	−0.135	0.603	0.771 *	0.775 *	0.546	0.551	0.571	0.309	−0.696 *

* significant correlation (p < 0.05); ** extremely significant correlation (p < 0.01).

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Share and Cite

MDPI and ACS Style

Li, Y.; Sun, X.; He, K.; Jin, X.; Leng, J.; Huang, Q.; Liu, J.; Sheng, Y. Analysis of Salt Tolerance of ‘Golden Gold’ Peach Varieties. Agronomy 2024, 14, 3034. https://doi.org/10.3390/agronomy14123034

AMA Style

Li Y, Sun X, He K, Jin X, Leng J, Huang Q, Liu J, Sheng Y. Analysis of Salt Tolerance of ‘Golden Gold’ Peach Varieties. Agronomy. 2024; 14(12):3034. https://doi.org/10.3390/agronomy14123034

Chicago/Turabian Style

Li, Yang, Xiaoming Sun, Kailong He, Xuebin Jin, Jiachen Leng, Qinglin Huang, Jin Liu, and Yinsheng Sheng. 2024. "Analysis of Salt Tolerance of ‘Golden Gold’ Peach Varieties" Agronomy 14, no. 12: 3034. https://doi.org/10.3390/agronomy14123034

APA Style

Li, Y., Sun, X., He, K., Jin, X., Leng, J., Huang, Q., Liu, J., & Sheng, Y. (2024). Analysis of Salt Tolerance of ‘Golden Gold’ Peach Varieties. Agronomy, 14(12), 3034. https://doi.org/10.3390/agronomy14123034

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Menu