Identification of a Novel Salt Tolerance-Related Locus in Wild Soybean (Glycine soja Sieb. & Zucc.)

Salinity is an important abiotic stress factor that affects growth and yield of soybean. NY36-87 is a wild soybean germplasm with high salt tolerance. In this study, two F2:3 mapping populations derived from NY36-87 and two salt-sensitive soybean cultivars, Zhonghuang39 and Peking, were used to map salt tolerance-related genes. The two populations segregated as 1 (tolerant):2 (heterozygous):1 (sensitive), indicating a Mendelian segregation model. Using simple sequence repeat (SSR) markers together with the bulked segregant analysis (BSA) mapping strategy, we mapped a salt tolerance locus on chromosome 03 in F2:3 population Zhonghuang39×NY36-87 to a 98-kb interval, in which the known gene GmSALT3 co-segregated with the salt tolerance locus. In the F2:3 population of Peking×NY36-87, the dominant salt tolerance-associated gene was detected and mapped on chromosome 18. We named this gene GmSALT18 and fine mapped it to a 241-kb region. Time course analysis and a grafting experiment confirmed that Peking accumulated more Na+ in the shoot via a root-based mechanism. These findings reveal that the tolerant wild soybean line NY36-87 contains salt tolerance-related genes GmSALT3 and GmSALT18, providing genetic material and a novel locus for breeding salt-tolerant soybean.

Genetic Evidence of Stable Northward Extension of Pinus Thunbergii Forests in the Democratic People’s Republic Korea

Japanese black pine with high salt tolerance may be an important constitutive element sustaining terrestrial ecosystem by playing a role of windbreak forests in coastal areas. Korean peninsula would be a notable region in clarifying distribution shift in Pinus species as it has northern distribution limit of Japanese black pine in Asia. Our main object was to verify genetic evidence of stable northward extension of P.thunbergii populations in D. P. R. Korea. We investigated genetic background of 9 populations existing in Korean peninsula using nuclear SSR markers in relation to shifts in climate factors such as temperature and precipitation. Higher genetic diversity in east group (AR=10.7~19.5) and west group (AR=10.3~10.7) compared to north group (AR=6.7~8.8) was found. When number of putative clusters (K) = 2, whole individuals were divided into west group and north-east group, and when K=3, north-east group can be separated into north group and east group. Phylogeographic relationship verified by means of nSSR markers suggest that substantial increment of air temperature in D. P. R. Korea allowed stable anthropogenic transfer of P.thunbergii forests and that artificial afforestation may bring rapid establishment of forest ecosystem owing to climate change.

Physiological analysis reveals relatively higher salt tolerance in roots of Ilex integra than in those of Ilex purpurea

Determining the responses of candidate plants to salt stress is a prerequisite for selecting and breeding suitable plants with high salt tolerance to grow in coastal mudflat areas with high salinity. Here, 2-year cutting seedlings of Ilex purpurea Hassk. (local species) and I. integra Thunb. (introduced species) were grown in pots in a glasshouse and irrigated with a Hoagland-NaCl solution at 0, 24, and 48 h. Root samples were collected at 0, 1, 6, 24, and 72 h, and concentration of Na+ ion; content of proline, soluble carbohydrate, malondialdehyde (MDA), H2O2 and ascorbate; and activity of three key antioxidative enzymes were measured. Roots of I. integra accumulated relatively less Na+ and had less membrane lipid peroxidation and H2O2 during salt stress, thus indicating a relatively higher salt tolerance than roots of I. purpurea. Values for ascorbate content and antioxidant enzymatic activity suggest that the antioxidant ascorbate and antioxidative catalase may play substantial roles for scavenging reactive oxygen species in I. integra roots during salt treatment. Thus, I. integra is apparently more suitable for growing in local highly saline coastal mudflats.

Discovery of Endophytic Strains With Excellent Antagonism to Colletotrichum Scovillei in Sweet Pepper and Study on Their Biological Functions

Anthracnose caused by Colletotrichum spp. is a well-known disease that causes severe losses in pepper production which is used as a spice for thousands of households in many parts of China. With the biological control properties of endophytic strains have been developed and used have been of great importance in the prevention and control of anthracnose and environmental protection. Therefore, to control the pathogen Colletotrichum scovillei more safely, 58 endophytic strains were isolated from pepper leaves in this experiment. Plate resistance method was used to screen the antagonistic strains of C. scovillei, and it was found that the inhibition rate of 25 antagonistic strains against C. scovillei was greater than 60%, and the inhibitory rates of L1-7 and L3-5 against it were 79% and 80%, respectively. They were identified as Bacillus amyloliquefaciens and Bacillus velezensis by culture and morphological identification, combined with 16S rDNA and gyrB gene sequence analysis. The two antagonistic endophytic bacteria also had the ability to fix nitrogen and secrete IAA, and all had high salt tolerance. Controlled pot experiments in the laboratory showed that L1-7 and L3-5 had a good control effect against C. scovillei, with the control efficiency reaching 80.64% and 73.39%, respectively. Thus, B. amyloliquefaciens (L1-7) and B. velezensis (L3-5) could be useful as biological control agents to protect peppers from anthracnose disease caused by C. scovillei. The results of this test provide a basis for the development of pepper endophytic bacterial resources, and also bacterial resources for the biological control of C. scovillei.

Responses of Peppermint and Spearmint Crops to Excessive Biostimulant Application and Increased Salinity in a Closed Soilless Production System

A floating system was established in a heated glass greenhouse in order to investigate whether the effect of amino acids (0.25 or 0.50% of a commercial amino acid (AA) solution Amino16®) during peppermint and spearmint production on plant developmental and nutritional status may be in part attributed to salinity induced osmotic stress. For this reason, in some nutrient solutions, three levels of salinity were induced by adding 0, 10, or 20 mM NaCl. According to the results, it can be concluded that spearmint is mostly favored by the highest amino acid supplement of the nutrient solution (0.50%) in terms of a substantial improvement of the antioxidant nutritional quality (by up to 130%) at the expense of a reduced biomass production (by <30%). Enzymic antioxidant defense mechanism (APX and POD) was efficiently activated, preventing severe lipid peroxidation and the accumulation of reactive oxygen species such as H2O2 and maintaining the proline content at the normal levels. The osmotic stress that was induced by the excessive AA concentration and confirmed by the chlorophyl fluorescence variations was probably related to NH4+ excess supply in the growing media and was not associated with the elevated electrical conductivity in the solution. The absence of any adverse stressful consequences upon the addition of 20 mM NaCl may be attributed to the high salt tolerance of peppermint and spearmint species.

New Regression Model for Estimating Irrigation Water Quality Index

The common tool to evaluate the groundwater quality is so-called the Irrigation Water Quality Index (IWQI). In the present study, the IWQI model developed by Meireles is used to assess the quality of groundwater in Karbala - Najaf plateau, Iraq. The quality parameters that collected from groundwater tests of 78 wells in the study area are; EC, Na+1, Mg+2, Ca+2, Cl-1, and HCO3-1. The SPSS software program is employed to develop a non-linear regression model of the IWQI for the study area. The results show that the IWQI values for 90% of groundwater wells fall within the Severe Restriction (SR) category, which means that it’s only suitable for irrigation of high salt tolerance crops. While its remaining 10% of the wells are in the High Restriction (HR) category, and this means it is suitable for irrigation of moderate to high salt tolerance crops. The calibration and validation for the developed model presented that this model has a good estimation of the IWQI values. Due to flexible and unbiased, the current study recommends to use the proposed model to estimate the IWQI.

Characterization of a Yellow Laccase from Botrytis cinerea 241

Typical laccases have four copper atoms, which form three different copper centers, of which the T1 copper is responsible for the blue color of the enzyme and gives it a characteristic absorbance around 610 nm. Several laccases have unusual spectral properties and are referred to as yellow or white laccases. Only two yellow laccases from the Ascomycota phylum have been described previously, and only one amino acid sequence of those enzymes is available. A yellow laccase Bcl1 from Botrytis cinerea strain 241 has been identified, purified and characterized in this work. The enzyme appears to be a dimer with a molecular mass of 186 kDa. The gene encoding the Bcl1 protein has been cloned, and the sequence analysis shows that the yellow laccase Bcl1 is phylogenetically distinct from other known yellow laccases. In addition, a comparison of amino acid sequences, and 3D modeling shows that the Bcl1 laccase lacks a conservative tyrosine, which is responsible for absorption quenching at 610 nm in another yellow asco-laccase from Sclerotinia sclerotiorum. High thermostability, high salt tolerance, broad substrate specificity, and the ability to decolorize dyes without the mediators suggest that the Bcl1 laccase is a potential enzyme for various industrial applications.

Unraveling the Strategies Used by the Underexploited Amaranth Species to Confront Salt Stress: Similarities and Differences With Quinoa Species

Yield losses due to cultivation in saline soils is a common problem all over the world as most crop plants are glycophytes and, hence, susceptible to salt stress. The use of halophytic crops could be an interesting alternative to cope with this issue. The Amaranthaceae family comprises by far the highest proportion of salt-tolerant halophytic species. Amaranth and quinoa belong to this family, and their seeds used as pseudo-cereal grains have received much attention in recent years because of their exceptional nutritional value. While advances in the knowledge of salt tolerance mechanisms of quinoa have been remarkable in recent years, much less attention was received by amaranth, despite evidences pointing to amaranth as a promising species to be grown under salinity. In order to advance in the understanding of strategies used by amaranth to confront salt stress, we studied the comparative responses of amaranth and quinoa to salinity (100 mM NaCl) at the physiological, anatomical, and molecular levels. Amaranth was able to exhibit salt tolerance throughout its life cycle, since grain production was not affected by the saline conditions applied. The high salt tolerance of amaranth is associated with a low basal stomatal conductance due to a low number of stomata (stomatal density) and degree of stomata aperture (in adaxial surface) of leaves, which contributes to avoid leaf water loss under salt stress in a more efficient way than in quinoa. With respect to Na+ homeostasis, amaranth showed a pattern of Na+ distribution throughout the plant similar to glycophytes, with the highest accumulation found in the roots, followed by the stem and the lowest one detected in the leaves. Contrarily, quinoa exhibited a Na+ includer character with the highest accumulation detected in the shoots. Expression levels of main genes involved in Na+ homeostasis (SOS1, HKT1s, and NHX1) showed different patterns between amaranth and quinoa, with a marked higher basal expression in amaranth roots. These results highlight the important differences in the physiological and molecular responses of amaranth and quinoa when confronted with salinity.

Differential Accumulation of Metabolites in Suaeda Species Provides New Insights into Abiotic Stress Tolerance in C4-Halophytic Species in Elevated CO2 Conditions

Halophytic plants can adapt to grow and thrive in highly saline conditions. Suaeda species are annual halophytes with high salt tolerance and are most suitable in the restoration of salinized or contaminated saline land and as food, forage, medicine, and bioenergy. In this study, we comprehensively analyzed the different metabolic responses of Suaeda species under salt and drought stress at ambient and elevated CO2 conditions. Seedlings of Suaeda species were treated with 500 mM NaCl and 5% of polyethylene glycol under elevated CO2 stress conditions for 24 h. Then, widely untargeted metabolites were detected by gas chromatography–mass spectrometry. Different metabolites involved in amino acid metabolism, glycolysis, photorespiration, and tricarboxylic acid cycle were quantitatively determined after stress treatments. A total of 61 primary metabolites were annotated. Different treatments increased the contents of certain metabolites, such as amino acids, sugars, and organic acids, as well as some antioxidants, such as quininic acid, kaempferol, and melatonin. These substances may be correlated with osmotic tolerance, increased antioxidant activity, and medical and nutritional value in the species. This study suggests that various metabolites differentially accumulated in C4Suaeda species under varying stress conditions. Furthermore, this work provides new insights into the key secondary metabolite pathway involved in stress tolerance.

Functional Characteristics of The Stelar K+ Outward Rectifying Channel (EeSKOR) Gene in Elytrigia Elongata

As an important nutrient, K+ plays a crucial role in plant stress resistance. It has been reported that the stelar K+ outward rectifying channel (SKOR) is involved in loading K+ into the xylem for its transport from roots to shoots. Elytrigia elongata is a perennial, sparsely distributed, rhizome-type herbaceous plant belonging to the wheatgrass family; it has high salt tolerance. Here, we isolated EeSKOR from decaploid E. elongata and investigated its function in transgenic tobacco. The results showed that EeSKOR was mainly expressed in the roots and was up-regulated with increasing salinity and drought intensity. Overexpression of EeSKOR in plants exposed to salt stress enhanced growth performance, increased SOD activity and chlorophyll content, significantly reduced H2O2 and MDA content, reduced Na+ concentration, and increased K+ concentration in transgenic tobacco plants compared with wild-type (WT) and null vector (Vector) plants. Our findings suggest that transgenic plants overexpressing EeSKOR could enhance K+ transport from the roots to the aboveground parts to maintain K+ steady-state in the aboveground under conditions of salt stress, thereby enhancing tobacco salt tolerance.