Physiological responses of three soybean species (<Emphasis Type="Italic">Glycine soja,G. gracilis</Emphasis>, and <Emphasis Type="Italic">G. max</Emphasis> cv. Melrose) to salinity stress

Understanding the mechanism for salt tolerance in wild soybean (Glycine soja) can help researchers improve that trait in cultivated soybean lines. We analyzed the effects of excess NaCl on the growth, physiology, and ion distribution in three soybean species: wild G. soja (W8), semi-wild G. gracilis (SW18), and the cultivated salt-sensitive G. max (cv. Melrose). These comparisons revealed that, under salt stress, shoot and root lengths and biomass (either shoot or root dry weights) were significantly higher for the W8 genotype than for the other two. Most of the morphological parameters for roots from the W8 plants were also increased, including total length, specific root length, and surface area. However, the average root diameter for W8 was significantly lower than that of either SW18 or ‘Melrose’ soybeans. In response to salinity, photosynthesis was suppressed to a greater extent in ‘Melrose’ than in W8. The relatively higher tolerance shown by W8 plants was also associated with lower levels of malondialdehyde, hydrogen peroxide, and relative electrical conductivity, but higher activities by superoxide dismutase and peroxidase, as well as more free proline and glycine betaine. In addition, the W8 plants contained less Na⁺ and Cl^?, but more K⁺, and they had a higher K⁺/Na⁺ ratio in their leaves and roots when compared with either SW18 or ‘Melrose’ plants. Therefore, the W8 genotype performs better in terms of seedling growth, photosynthetic characteristics, and physiological indexes. These findings provide guidance for developing new soybean cultivars with improved tolerance to salt stress. Our data also contribute to the knowledge base for plant salt tolerance as a tool for increasing the yields of other crops in high-salinity soils.     

Physiological Mechanisms for High Salt Tolerance in Wild Soybean (Glycine soja) from Yellow River Delta,China: Photosynthesis,Osmotic Regulation,Ion Flux and antioxidant Capacity

Glycine soja (BB52) is a wild soybean cultivar grown in coastal saline land in Yellow River Delta, China. In order to reveal the physiological mechanisms adapting to salinity, we examined photosynthesis, ion flux, antioxidant system and water status in Glycine soja under NaCl treatments, taking a cultivated soybean, ZH13, as control. Upon NaCl exposure, higher relative water content and water potential were maintained in the leaf of BB52 than ZH13, which might depend on the more accumulation of osmotic substances such as glycinebetaine and proline. Compared with ZH13, activities of antioxidant enzymes including superoxide dismutase, catalase, ascorbate peroxidase and contents of ascorbate, glutathione and phenolics were enhanced to a higher level in BB52 leaf under NaCl stress, which could mitigate the salt-induced oxidative damage in BB52. Consistently, lipid peroxidation indicated by malondialdehyde content was lower in BB52 leaf. Photosynthetic rate (Pn) was decreased by NaCl stress in BB52 and ZH13, and the decrease was greater in ZH13. The decreased Pn in BB52 was mainly due to stomatal limitation. The inhibited activation of rubisco enzyme in ZH13 due to the decrease of rubisco activase content became an important limiting factor of Pn, when NaCl concentration increased to 200 mM. Rubisco activase in BB52 was not affected by NaCl stress. Less negative impact in BB52 derived from lower contents of Na⁺ and Cl^- in the tissues, and non-invasive micro-test technique revealed that BB52 roots had higher ability to extrude Na⁺ and Cl^-. Wild soybean is a valuable genetic resource, and our study may provide a reference for molecular biologist to improve the salt tolerance of cultivated soybean in face of farmland salinity.     

The influence of salinity on cell ultrastructures and photosynthetic apparatus of barley genotypes differing in salt stress tolerance

A hydroponic experiment was conducted to elucidate the difference in growth and cell ultrastructure between Tibetan wild and cultivated barley genotypes under moderate (150 mM NaCl) and high (300 mM NaCl) salt stress. The growth of three barley genotypes was reduced significantly under salt stress, but the wild barley XZ16 (tolerant) was less affected relative to cultivated barley Yerong (moderate tolerant) and Gairdner (sensitive). Meanwhile, XZ16 had lower Na⁺ and higher K⁺ concentrations in leaves than other two genotypes. In terms of photosynthetic and chlorophyll fluorescence parameters, salt stress reduced maximal photochemical efficiency (F _v/F _m), net photosynthetic rate (Pn), stomatal conductance (Gs), and intracellular CO₂ concentration (Ci). XZ16 showed relatively smaller reduction in comparison with the two cultivated barley genotypes. The observation of transmission electron microscopy found that fundamental cell ultrastructure changes happened in both leaves and roots of all barley genotypes under salt NaCl stress, with chloroplasts being most changed. Moreover, obvious difference could be detected among the three genotypes in the damage of cell ultrastructure under salt stress, with XZ16 and Gairdner being least and most affected, respectively. It may be concluded that high salt tolerance in XZ16 is attributed to less Na⁺ accumulation and K⁺ reduction in leaves, more slight damage in cell ultrastructure, which in turn caused less influence on chloroplast function and photosynthesis.     

Different Effect of Humidity on Growth and Salt Tolerance of Two Soybean Cultivars

Two soybean (Glycine max (L.) Merr.) cultivars, Tachiyutaka and Dare, were grown in pots at 30 and 70 % relative humidity (RH) and treated with 0 (control), 40 (moderate), 80 and 120 (severe) mM NaCl for 3 weeks. Increasing RH enhanced growth of salt sensitive cultivar, Tachiyutaka, but had no effect on salt tolerant cultivar, Dare, under control and moderate saline conditions. Both cultivars benefited from elevated humidity under severe saline conditions. Cultivar Tachiyutaka had poorer ability for controlling translocation of Na⁺ to the leaves, lower Na⁺ exclusion ability in the roots, and lower root activity under NaCl treatment, compared with cv. Dare. The increased growth of cv. Tachiyutaka at high RH was consistent with decreased Na⁺ accumulation in the leaves, increased stomatal conductance and root activity, while the unchanged growth of cv. Dare was consistent with similar Na⁺ accumulation in the leaves, and the decreased root activity.     

Effects of salt stress and exogenous Ca2+ on Na+ compartmentalization,ion pump activities of tonoplast and plasma membrane in Nitraria tangutorum Bobr. leaves

Nitraria tangutorum Bobr. is a typical halophyte with superior tolerance to salinity. However, little is known about its physiological adaptation mechanisms to the salt environment. In the present study, N. tangutorum seedlings were treated with different concentrations of NaCl (100, 200, 300 and 400 mmol L^?1) combined with five levels of Ca²⁺ (0, 5, 10, 15 and 20 mmol L^?1) to investigate the effects of salt stress and exogenous Ca²⁺ on Na⁺ compartmentalization and ion pump activities of tonoplast and plasma membrane (PM) in leaves. Na⁺ and Ca²⁺ treatments increased the fresh weight and dry weight of N. tangutorum seedlings. The absorption of Na⁺ in roots, stems and leaves was substantially increased with the increases of NaCl concentration, and Na⁺ was mainly accumulated in leaves. Exogenous Ca²⁺ reduced Na⁺ accumulation in roots but promoted Na⁺ accumulation in leaves. The absorption and transportation of Ca²⁺ in N. tangutorum seedlings were inhibited under NaCl treatments. Exogenous Ca²⁺ promoted Ca²⁺ accumulation in the plant. Na⁺ contents in apoplast and symplast of leaves were also significantly increased, and symplast was the main part of Na⁺ intracellular compartmentalization. The tonoplast H⁺-ATPase and H⁺-PPase activities were significantly promoted under salt stress (NaCl concentrations ≤300 mmol L^?1). PM H⁺-ATPase activities gradually increased under salt stress (NaCl concentrations ≤200 mmol L^?1) followed by decreases with NaCl concentration increasing. The tonoplast H⁺-ATPase, H⁺-PPase and PM H⁺-ATPase activities increased first with the increasing exogenous Ca²⁺ concentration, reached the maximums at 15 mmol L^?1 Ca²⁺, and then decreased. The tonoplast and PM Ca²⁺-ATPase activities showed increasing trends with the increases of NaCl and Ca²⁺ concentration. These results suggested that certain concentrations of exogenous Ca²⁺ effectively enhanced ion pump activities of tonoplast and PM as well as promoted the intracellular Na⁺ compartmentalization to improve the salt tolerance of N. tangutorum.     

野生大豆耐盐性研究进展

野生大豆对于拓宽大豆种质遗传基础和丰富大豆种质基因库具有重要意义.该文从野生大豆的资源概况及优良性状、耐盐机理和利用野生大豆提高栽培大豆耐盐性等三个方面,对近年来国内外有关野生大豆耐盐性的解剖结构、生理基础、分子生物学基础等方面的研究进展进行了系统综述,并提出野生大豆通过茎叶表皮上的"腺体"及对Na+和Cl-的排斥性,实现对盐渍环境的颉颃作用.较强的抗氧化能力、大豆异黄酮代谢和耐盐基因也是其适应盐渍环境的重要原因.今后应对野生大豆耐盐机理的遗传学基础进行深入研究,并通过种群保护以保障野生大豆的发掘鉴定和创新利用.     

Nucleotide diversity of the upstream region of the putative MADS-box gene controlling soybean maturity

MADS-box genes are involved in plant reproductive development. However, the role of gene nucleotide diversity in soybean flowering and maturity remains unknown. Therefore, in this study, the distribution of DNA polymorphisms in the putative MADS-box gene located near the quantitative trait loci (QTL) for flowering time and maturity was targeted for association analysis using Glycine max (cultivated soybean) and Glycine soja (wild soybean). Sixteen single nucleotide polymorphisms identified in the upstream region of the putative MADS-box gene around QTL Pod mat 13-7 and Fflr 4-2 on chromosome 7 were found to be highly associated with maturity in soybean. The genetic diversity between cultivated soybeans and the wild relative was comparable, although the early maturity group (EMG) was less diverse than the late maturity group (LMG) of the cultivated soybean. Population size changes of the MADS-box gene in this soybean germplasm appeared to result from non-random selection. A selective pressure seemed to act on this gene in the EMG, while the LMG and G. soja were in genetic equilibrium. Neutrality tests and the constructed neighbor-joining tree indicate that the EMG of G. max has experienced strong artificial selection for its domestication and genetic improvement.     

Salt resistance in two cashew species is associated with accumulation of organic and inorganic solutes

This study establishes relationships between salt resistance and solute accumulation in roots and leaves of two contrasting cashew species. The sensitive (Anacardium microcarpum) and resistant (A. occidentale) species showed maximum root LD₅₀ values (the external NaCl concentration required for a 50% reduction in dry weight) of 63 and 128?mM NaCl, whereas the shoot LD₅₀ values were 90 and 132?mM, respectively. The salt sensitivity was directly associated with Na⁺ accumulation and especially with the Cl^? content in leaves and to a minor extent in roots. The accumulation of saline ions was associated with higher net uptake rates by roots and transport rates from root to shoot in the sensitive cashew species. The K⁺/Na⁺ ratios were not associated with salt resistance either in roots or leaves. Proline and free amino acid concentrations were strongly increased by salinity, especially in the leaves of the resistant species. The soluble sugar concentrations were not influenced by NaCl treatments in leaves of both species. In contrast, the root soluble sugar content was significantly decreased by salinity in the sensitive species only. In conclusion, the higher salt sensitivity of A. microcarpum is associated to an inefficient salt exclusion system of the leaves, especially for Cl^?. On the other hand, the resistant species displays higher concentrations of organic solutes especially a salt-induced accumulation of proline and free amino acids in leaves.     

Uncovering signatures of selection in the soybean genome using SSR diversity near QTLs of agronomic importance

The cultivated soybean [Glycine max (L.) Merr.] is widely considered to descend from the wild soybean (G. soja Sieb. & Zucc.). This study was designed to evaluate the genetic variability and differentiation between G. soja and G. max, and to detect signatures of the selection that may have occurred during the domestication process from G. soja to G. max. A total of 192 G. soja accessions and 104 G. max accessions were genotyped using eight selected simple sequence repeat (SSR) markers assigned to three SSR groups. Four SSRs in group A were not located near any known QTL. Three SSRs in group B were associated with seed protein content, and an SSR in group C was associated with resistance to Sclerotinia stem rot. The number of alleles per locus and the level of genetic variability in G. soja were higher than those in G. max. A total of 122 out of 125 alleles were present in G. soja, but only 59 alleles were detected in G. max. The average gene diversity was 0.74 in G. soja and 0.64 in G. max. Four SSRs near QTLs of agronomic importance showed strong genetic differentiation and shift change in high frequency alleles in groups B and C between G. soja and G. max, revealing selection signatures that may reflect the domestication events and recent selective breeding. With reduced diversity in G. max, some undomesticated genes from G. soja should be prime candidates for introgression to increase the pool of diversity in G. max.     

Influence of exogenous application of glycinebetaine on antioxidative system and growth of salt-stressed soybean seedlings (Glycine max L.)

Glycinebetaine is one of the most competitive compounds which play an important role in salt stress in plants. In this study, the enhanced salt tolerance in soybean (Glycine max L.) by exogenous application of glycinebetaine was evaluated. To improve salt tolerance at the seedling stage, GB was applied in four different concentrations (0, 5, 25 and 50 mM) as a pre-sowing seed treatment. Salinity stress in the form of a final concentration of 150 mM sodium chloride (NaCl) over a 15 day period drastically affected the plants as indicated by increased proline, MDA and Na⁺ content of soybean plants. In contrast, supplementation with 50 mM GB improved growth of soybean plants under NaCl as evidenced by a decrease in proline, MDA and Na⁺ content of soybean plants. Further analysis showed that treatments with GB, resulted in increasing of CAT and SOD activity of soybean seedlings in salt stress. We propose that the role of GB in increasing tolerance to salinity stress in soybean may result from either its antioxidant capacity by direct scavenging of H₂O₂ or its role in activating CAT activity which is mandatory in scavenging H₂O₂.     

Effects of NaCl stress on the growth and photosynthetic characteristics of Ulmus pumila L. seedlings in sand culture

The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na⁺ content and the Na⁺/K⁺ ratio in both expanded and expanding leaves increased. Na⁺ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na⁺ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation.     

Induction of cyclic electron flow around photosystem 1 and state transition are correlated with salt tolerance in soybean

We investigated the role of cyclic electron flow around photosystem 1 (CEF1) and state transition (ST) in two soybean cultivars that differed in salt tolerance. The CEF1 and maximum photochemical efficiency (F_v/F_m) were determined under control and NaCl (50 mM) stress and the NaCl-induced light-harvesting complex 2 (LHC2) phosphorylation in vitro was analysed in light and dark. NaCl induced the increase of CEF1 more greatly in wild soybean Glycine cyrtoloba (cv. ACC547) than in cultivated soybean Glycine max (cv. Melrose). The F_v/F_m was reduced less in G. cyrtoloba than in G. max after 10-d NaCl stress. In G. cyrtoloba, the increase of CEF1 was associated with enhancement of LHC2 phosphorylation in thylakoid membrane under both dark and light. However, in G. max the NaCl treatment decreased the LHC2 phosphorylation. Treatment with photosynthetic electron flow inhibitors (DCMU, DBMIB) inhibited LHC2 phosphorylation more in G. max than in G. cyrtoloba. Thus the NaCl-induced up-regulation in CEF1 and ST might contribute to salt resistance of G. cyrtoloba.     

Significance of Na<Superscript>+</Superscript> and K<Superscript>+</Superscript> for Sustained Hydration of Organ Tissues in Ecologically Distinct Halophytes of the Family Chenopodiaceae

The contents of Na⁺, K⁺, water, and dry matter were measured in leaves and roots of euhalophytes Salicornia europaea L. and Climacoptera lanata (Pall.) Botsch featuring succulent and xeromorphic cell structures, respectively, as well as in saltbush Atriplex micrantha C.A. Mey, a halophyte having bladder-like salt glands on their leaves. All three species were able to accumulate Na⁺ in their tissues. The Na⁺ content in organs increased with elevation of NaCl concentration in the substrate, the concentrations of Na⁺ being higher in leaves than in roots. When these halophytes were grown on a NaCl-free substrate, a trend toward K⁺ accumulation was observed and was better pronounced in leaves than in roots. Particularly high K⁺ concentrations were accumulated in Salicornia leaves. There were no principal differences in the partitioning of Na⁺ and K⁺ between organs of three halophyte species representing different ecological groups. At all substrate concentrations of NaCl, the total content of Na⁺ and K⁺ in leaves was higher than in roots. This distribution pattern persisted in Atriplex possessing salt glands, as well as in euhalophytes Salicornia and Climacoptera. The physiological significance of such universal pattern of ion accumulation and distribution among organs in halophytes is related to the necessity of water absorption by roots, its transport to shoots, and maintenance of sufficient cell water content in all organs under high soil salinity.     

Study of the biosafety of genetically modified soybean in the center of its origin and diversity in the Far East of the Russian Federation

Wild soybean (Glycine soja Sieb. and Zucc.) is the nearest relative of cultivated soybean (G. max (L.) Merr.). Study of the population genetic structure of wild-growing relatives of genetically modified (GM) plants in the centers of their origin is one of the main procedures before introduction of GM crops in these areas. We studied the genetic variability of nine wild-growing soya populations of Primorskii krai using RAPD analysis. The level of genetic variability of G. soja was considerably higher than that of G. max. We analyzed phylogenetic relationships in the genus Glycine subgenus Soja using RAPD markers. Our data confirm the validity of allocation to G. gracilis of the rank of species.     

高盐生境中乌拉尔甘草盐离子分泌与积存格局的研究

采用植物水培方法,以乌拉尔甘草为研究材料,用不同浓度(0、80、160、320mmol·L~(-1))NaCl溶液胁迫处理乌拉尔甘草幼苗3周后,分析其叶片表面盐离子(K~+、Ca~(2+)、Na+)分泌速率的差异,并采集盐化低地草甸重盐土生境中2年生乌拉尔甘草植株,应用ICP-AES测定其不同部位(根、根状茎、茎、老叶和幼叶)中的盐离子(K~+、Na~+、Ga~(2+)、Mg~(2+))含量,探究盐离子在乌拉尔甘草叶片上的分泌格局以及盐离子在植株体内的积存格局,为完善甘草耐盐机理的研究提供依据。结果显示:(1)随着盐胁迫浓度的升高,乌拉尔甘草叶片上K~+、Ca~(2+)、Na+的分泌速率均呈增加趋势,且Na~+的分泌速率远远大于Ca~(2+)和K+的分泌速率。(2)在乌拉尔甘草各部位中,K+的积存量从大到小依次为:幼叶根根状茎茎老叶;Na~+在各个部位的积存量都十分有限,且无论地下部分还是地上部分,差异均不大;Ca~(2+)积存量由大到小依次为:老叶幼叶茎根状茎根,且老叶中Ca~(2+)的积存量显著高于其它部位。研究认为,在重盐碱地生境中,K+主要积存在幼叶中,Ga~(2+)主要积存在老叶中,植株体内各个部位Na~+的积存量很低,乌拉尔甘草表现出明显的拒Na现象;叶片分泌的主要盐离子为Na~+;乌拉尔甘草通过泌盐的方式将Na+排出体外,从而有效降低Na~+在体内的积存,这是其能够在重盐碱地生存生长的重要原因。     

Physiological adaptation and gene expression analysis of <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> under salt stress

Casuarina equisetifolia is widely planted in coastal areas of tropical and subtropical regions as windbreaks or to stabilize dunes against wind erosion due to its high salt tolerance and nitrogen-fixing ability. To investigate the mechanisms responsible for its salt tolerance, we examined growth, mineral composition, expression of genes for sodium (Na⁺) and potassium (K⁺) transport proteins, and antioxidant responses under NaCl treatments. Increasing NaCl concentrations inhibited lateral root elongation and decreased plant height, length of internodes, and numbers of branches and twigs. The Na⁺ content significantly increased whereas the K⁺ content significantly decreased in both shoots and roots with increasing external NaCl concentration, resulting in a significant increase in Na⁺/K⁺ ratio. Most of the Na⁺/H⁺ antiporter genes (NHXs) were obviously upregulated in roots after 24 and 168 h of salt stress, and NHX7 was especially induced after 168 h. Almost all salt overly sensitive (SOS) genes were induced after 168-h treatment. Additionally, activities of superoxide dismutase, glutathione peroxidase, and catalase were significantly changed in shoots and roots under salt stress. Hence, we conclude that salinity tolerance of C. equisetifolia mainly relied on sequestering excess Na⁺ into vacuoles and on induced expression of NHX and SOS genes in roots and thus the maintenance of sufficient K⁺ content in shoots.     

Assessment of salt tolerance of Nasturtium officinale R. Br. using physiological and biochemical parameters

Nasturtium officinale R. Br. seedlings were treated with a range of NaCl concentrations (0, 50, 100 and 150 mM) for 21 days after seedling emergence. Physiological analysis based on growth and mineral nutrition, showed a substantial decrease in leaf dry matter with 150 mM NaCl treatment. The growth decrease was correlated with nutritional imbalance and a reduction in potassium accumulation and transport to the leaves. At the same time, we noted an increase in leaf sodium and chloride accumulation and transport. Salt tolerance of N. officinale under 100 mM NaCl was associated with osmotic adjustment via Na⁺ and Cl^? and the maintenance of high K⁺/Na⁺ selectivity. Salt decreased carotenoid content more than chlorophylls and also disturbed membrane integrity by increasing malondialdehyde content and electrolyte leakage. At 150 mM NaCl, an increase in antioxidant enzyme-specific activities for superoxide dismutase, catalase and guaiacol peroxidase occurred in concert with a decrease in ascorbic acid, polyphenol, tannin and flavonoid content. These results indicate that N. officinale can maintain growth and natural antioxidant defense compounds such as, vitamin C, carotenoids, and polyphenols, when cultivated in 100 mM NaCl, but not at higher salt levels.     

Salt-Induced Hypodermal Transfer Cells in Roots of Prosopis farcta and Ion Distribution within Young Plants

Prosopis farcta was grown on hydroculture with additions of 0.5, 10, 50, and 100 mM NaCl and without salt treatment. In plants from a 0.5 mM NaCl treatment, Cl^? was taken up into stems and leaves, but Na⁺ was withheld from the shoot. At 10 mM NaCl, shoot K⁺ concentration was below that of the control; Na⁺ and Cl^? were taken up to stems and cotyledons in nearly equimolar amounts. However, in the leaves, Na⁺ concentrations were only half of those of Cl^?. With increasing salt stress, Na⁺ and Cl^? were transported to the shoot, but kept at relatively low levels in the roots. Na⁺/ K⁺ ratios in roots did not increase proportionally to those in the solution. At an external Na⁺/K⁺ of > 5 and a root Na⁺/K⁺ of >1 (10 mM NaCl treatment), K⁺ selectivity was induced which rose exponentially with increasing salt stress; and cell wall protuberances were discovered in the hypodermis at the zone of side root formation. These transfer cells were found neither in roots from the 0.5 mM NaCl treatment nor in the controls. Their possible role in the Na⁺/K⁺ selectivity of the roots of Prosopis farcta is discussed.     

QTL affecting fitness of hybrids between wild and cultivated soybeans in experimental fields

The objective of this study was to identify quantitative trait loci (QTL) affecting fitness of hybrids between wild soybean (Glycine soja) and cultivated soybean (Glycine max). Seed dormancy and seed number, both of which are important for fitness, were evaluated by testing artificial hybrids of G. soja × G. max in a multiple‐site field trial. Generally, the fitness of the F₁ hybrids and hybrid derivatives from self‐pollination was lower than that of G. soja due to loss of seed dormancy, whereas the fitness of hybrid derivatives with higher proportions of G. soja genetic background was comparable with that of G. soja. These differences were genetically dissected into QTL for each population. Three QTLs for seed dormancy and one QTL for total seed number were detected in the F₂ progenies of two diverse cross combinations. At those four QTLs, the G. max alleles reduced seed number and severely reduced seed survival during the winter, suggesting that major genes acquired during soybean adaptation to cultivation have a selective disadvantage in natural habitats. In progenies with a higher proportion of G. soja genetic background, the genetic effects of the G. max alleles were not expressed as phenotypes because the G. soja alleles were dominant over the G. max alleles. Considering the highly inbreeding nature of these species, most hybrid derivatives would disappear quickly in early self‐pollinating generations in natural habitats because of the low fitness of plants carrying G. max alleles.